[PATCH v2 0/4] box: introduce hint option for memtx tree index

[PATCH v2 0/4] box: introduce hint option for memtx tree index

[Kirill Shcherbatov]

Reworked memtx tree to use 'tuple hints'.
Introduced special functions for retrieve tuple hints for a particular key_def.
Hint is an integer that can be used for tuple comparison optimization:
if a hint of one tuple is less than a hint of another then the first
tuple is definitely less than the second; only if hints are equal
tuple_compare must be called for getting comparison result.

Hints are only useful when:

* they are precalculated and stored along with the tuple;
  calculation is not cheap (cheaper than tuple_compare btw) but
  precalculated hints allow to compare tuples without even fetching
  tuple data.
* first part of key_def is 'string', 'unsigned' or 'integer'
* since hint is calculated using only the first part of key_def
  (and only first several characters if it is a string) this part
  must be different with high probability for every tuple pair.

Enabled hint option improve performance on average by 15%; Select operations
are significantly accelerated (there are scenarios in which the difference
reaches 200-250%).

Changes in version 2:
  -- Splitted patch to parts in other way to decrease diff
  -- Hints are not index option anymore, but default where possible
  -- Removed hints for numeric types

http://github.com/tarantool/tarantool/tree/kshch/gh-3961-tuple-hints
https://github.com/tarantool/tarantool/issues/3961

Alexandr Lyapunov (1):
  box: introduce tuple compare hint for string index

Kirill Shcherbatov (3):
  box: move memtx_tree implementation to source file
  box: rework memtx_tree to store arbitrary nodes
  box: rename memtx_tree.c to memtx_tree_impl.h

 src/box/CMakeLists.txt                      |   2 +-
 src/box/key_def.c                           |   1 +
 src/box/key_def.h                           |  44 ++
 src/box/memtx_tree.h                        |  68 +--
 src/box/memtx_tree_decl.c                   | 207 +++++++++
 src/box/{memtx_tree.c => memtx_tree_impl.h} | 490 +++++++++++++++-----
 src/box/tuple_compare.cc                    | 101 ++++
 src/box/tuple_compare.h                     |   7 +
 src/coll.c                                  |  45 ++
 src/coll.h                                  |   4 +
 10 files changed, 787 insertions(+), 182 deletions(-)
 create mode 100644 src/box/memtx_tree_decl.c
 rename src/box/{memtx_tree.c => memtx_tree_impl.h} (55%)

-- 
2.20.1

[PATCH v2 1/4] box: move memtx_tree implementation to source file

[Kirill Shcherbatov]

Refactored memtx_tree code so that memtx_tree.h contained only
the signature of the tree object constructor memtx_tree_index_new,
while all implementation details were in memtx_tree.c.
This will further allow to template the implementation details.

Needed for #3961
---
 src/box/memtx_tree.c | 62 ++++++++++++++++++++++++++++++++++++++--
 src/box/memtx_tree.h | 68 ++------------------------------------------
 2 files changed, 63 insertions(+), 67 deletions(-)

diff --git a/src/box/memtx_tree.c b/src/box/memtx_tree.c
index f851fb869..2e8adb682 100644
--- a/src/box/memtx_tree.c
+++ b/src/box/memtx_tree.c
@@ -39,6 +39,64 @@
 #include <third_party/qsort_arg.h>
 #include <small/mempool.h>
 
+/**
+ * Struct that is used as a key in BPS tree definition.
+ */
+struct memtx_tree_key_data {
+	/** Sequence of msgpacked search fields. */
+	const char *key;
+	/** Number of msgpacked search fields. */
+	uint32_t part_count;
+};
+
+/**
+ * BPS tree element vs key comparator.
+ * Defined in header in order to allow compiler to inline it.
+ * @param tuple - tuple to compare.
+ * @param key_data - key to compare with.
+ * @param def - key definition.
+ * @retval 0  if tuple == key in terms of def.
+ * @retval <0 if tuple < key in terms of def.
+ * @retval >0 if tuple > key in terms of def.
+ */
+static int
+memtx_tree_compare_key(const struct tuple *tuple,
+		       const struct memtx_tree_key_data *key_data,
+		       struct key_def *def)
+{
+	return tuple_compare_with_key(tuple, key_data->key,
+				      key_data->part_count, def);
+}
+
+#define BPS_TREE_NAME memtx_tree
+#define BPS_TREE_BLOCK_SIZE (512)
+#define BPS_TREE_EXTENT_SIZE MEMTX_EXTENT_SIZE
+#define BPS_TREE_COMPARE(a, b, arg) tuple_compare(a, b, arg)
+#define BPS_TREE_COMPARE_KEY(a, b, arg) memtx_tree_compare_key(a, b, arg)
+#define bps_tree_elem_t struct tuple *
+#define bps_tree_key_t struct memtx_tree_key_data *
+#define bps_tree_arg_t struct key_def *
+
+#include "salad/bps_tree.h"
+
+#undef BPS_TREE_NAME
+#undef BPS_TREE_BLOCK_SIZE
+#undef BPS_TREE_EXTENT_SIZE
+#undef BPS_TREE_COMPARE
+#undef BPS_TREE_COMPARE_KEY
+#undef bps_tree_elem_t
+#undef bps_tree_key_t
+#undef bps_tree_arg_t
+
+struct memtx_tree_index {
+	struct index base;
+	struct memtx_tree tree;
+	struct tuple **build_array;
+	size_t build_array_size, build_array_alloc_size;
+	struct memtx_gc_task gc_task;
+	struct memtx_tree_iterator gc_iterator;
+};
+
 /* {{{ Utilities. *************************************************/
 
 static int
@@ -683,7 +741,7 @@ static const struct index_vtab memtx_tree_index_vtab = {
 	/* .end_build = */ memtx_tree_index_end_build,
 };
 
-struct memtx_tree_index *
+struct index *
 memtx_tree_index_new(struct memtx_engine *memtx, struct index_def *def)
 {
 	if (!mempool_is_initialized(&memtx->tree_iterator_pool)) {
@@ -707,5 +765,5 @@ memtx_tree_index_new(struct memtx_engine *memtx, struct index_def *def)
 	struct key_def *cmp_def = memtx_tree_index_cmp_def(index);
 	memtx_tree_create(&index->tree, cmp_def, memtx_index_extent_alloc,
 			  memtx_index_extent_free, memtx);
-	return index;
+	return &index->base;
 }
diff --git a/src/box/memtx_tree.h b/src/box/memtx_tree.h
index bbc8b2419..edeaebab9 100644
--- a/src/box/memtx_tree.h
+++ b/src/box/memtx_tree.h
@@ -30,78 +30,16 @@
  * THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  */
-#include <stddef.h>
-#include <stdint.h>
-
-#include "index.h"
-#include "memtx_engine.h"
 
 #if defined(__cplusplus)
 extern "C" {
 #endif /* defined(__cplusplus) */
 
+struct index;
+struct index_def;
 struct memtx_engine;
 
-/**
- * Struct that is used as a key in BPS tree definition.
- */
-struct memtx_tree_key_data
-{
-	/** Sequence of msgpacked search fields */
-	const char *key;
-	/** Number of msgpacked search fields */
-	uint32_t part_count;
-};
-
-/**
- * BPS tree element vs key comparator.
- * Defined in header in order to allow compiler to inline it.
- * @param tuple - tuple to compare.
- * @param key_data - key to compare with.
- * @param def - key definition.
- * @retval 0  if tuple == key in terms of def.
- * @retval <0 if tuple < key in terms of def.
- * @retval >0 if tuple > key in terms of def.
- */
-static inline int
-memtx_tree_compare_key(const struct tuple *tuple,
-		       const struct memtx_tree_key_data *key_data,
-		       struct key_def *def)
-{
-	return tuple_compare_with_key(tuple, key_data->key,
-				      key_data->part_count, def);
-}
-
-#define BPS_TREE_NAME memtx_tree
-#define BPS_TREE_BLOCK_SIZE (512)
-#define BPS_TREE_EXTENT_SIZE MEMTX_EXTENT_SIZE
-#define BPS_TREE_COMPARE(a, b, arg) tuple_compare(a, b, arg)
-#define BPS_TREE_COMPARE_KEY(a, b, arg) memtx_tree_compare_key(a, b, arg)
-#define bps_tree_elem_t struct tuple *
-#define bps_tree_key_t struct memtx_tree_key_data *
-#define bps_tree_arg_t struct key_def *
-
-#include "salad/bps_tree.h"
-
-#undef BPS_TREE_NAME
-#undef BPS_TREE_BLOCK_SIZE
-#undef BPS_TREE_EXTENT_SIZE
-#undef BPS_TREE_COMPARE
-#undef BPS_TREE_COMPARE_KEY
-#undef bps_tree_elem_t
-#undef bps_tree_key_t
-#undef bps_tree_arg_t
-
-struct memtx_tree_index {
-	struct index base;
-	struct memtx_tree tree;
-	struct tuple **build_array;
-	size_t build_array_size, build_array_alloc_size;
-	struct memtx_gc_task gc_task;
-	struct memtx_tree_iterator gc_iterator;
-};
-
-struct memtx_tree_index *
+struct index *
 memtx_tree_index_new(struct memtx_engine *memtx, struct index_def *def);
 
 #if defined(__cplusplus)
-- 
2.20.1

[PATCH v2 2/4] box: rework memtx_tree to store arbitrary nodes

[Kirill Shcherbatov]

Reworked memtx_tree class to use arbitrary containers as a tree
nodes. This makes possible to implement tuple hints in subsequent
patches.

The memtx_tree.c is currently used in a header manner. This is to
ensure that functional changes in the patch do not mix with
refactoring, that will be finished in the next commit.

Needed for #3961
---
 src/box/CMakeLists.txt    |   2 +-
 src/box/memtx_tree.c      | 498 ++++++++++++++++++++++++++------------
 src/box/memtx_tree_decl.c |  84 +++++++
 3 files changed, 434 insertions(+), 150 deletions(-)
 create mode 100644 src/box/memtx_tree_decl.c

diff --git a/src/box/CMakeLists.txt b/src/box/CMakeLists.txt
index 5521e489e..dc8cc2cd5 100644
--- a/src/box/CMakeLists.txt
+++ b/src/box/CMakeLists.txt
@@ -64,7 +64,7 @@ add_library(box STATIC
     index_def.c
     iterator_type.c
     memtx_hash.c
-    memtx_tree.c
+    memtx_tree_decl.c
     memtx_rtree.c
     memtx_bitset.c
     engine.c
diff --git a/src/box/memtx_tree.c b/src/box/memtx_tree.c
index 2e8adb682..0874b7dc8 100644
--- a/src/box/memtx_tree.c
+++ b/src/box/memtx_tree.c
@@ -1,5 +1,5 @@
 /*
- * Copyright 2010-2016, Tarantool AUTHORS, please see AUTHORS file.
+ * Copyright 2010-2019, Tarantool AUTHORS, please see AUTHORS file.
  *
  * Redistribution and use in source and binary forms, with or
  * without modification, are permitted provided that the following
@@ -28,72 +28,156 @@
  * THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  */
-#include "memtx_tree.h"
-#include "memtx_engine.h"
-#include "space.h"
-#include "schema.h" /* space_cache_find() */
-#include "errinj.h"
-#include "memory.h"
-#include "fiber.h"
-#include "tuple.h"
-#include <third_party/qsort_arg.h>
+
+#if defined(__cplusplus)
+extern "C" {
+#endif /* defined(__cplusplus) */
+
 #include <small/mempool.h>
+#include <third_party/qsort_arg.h>
+#include "memtx_engine.h"
+#include "schema.h"
 
-/**
- * Struct that is used as a key in BPS tree definition.
- */
-struct memtx_tree_key_data {
-	/** Sequence of msgpacked search fields. */
-	const char *key;
-	/** Number of msgpacked search fields. */
-	uint32_t part_count;
-};
+#ifndef MEMTX_TREE_NAME
+#error "MEMTX_TREE_NAME must be defined"
+#endif
+
+#ifndef memtx_tree_elem
+#error "memtx_tree_elem must be defined"
+#endif
+
+#ifndef memtx_tree_key
+#error "memtx_tree_key must be defined"
+#endif
+
+#ifndef MEMTX_TREE_ELEM_CMP
+#error "MEMTX_TREE_ELEM_CMP must be defined"
+#endif
+
+#ifndef MEMTX_TREE_ELEM_WITH_KEY_CMP
+#error "MEMTX_TREE_ELEM_WITH_KEY_CMP must be defined"
+#endif
+
+#ifndef MEMTX_TREE_ELEM_SET
+#error "MEMTX_TREE_ELEM_SET must be defined"
+#endif
+
+#ifndef MEMTX_TREE_KEY_SET
+#error "MEMTX_TREE_KEY_SET must be defined"
+#endif
+
+#ifndef MEMTX_TREE_ELEM_GET
+#error "MEMTX_TREE_ELEM_GET must be defined"
+#endif
+
+#ifndef MEMTX_TREE_KEY_GET
+#error "MEMTX_TREE_KEY_GET must be defined"
+#endif
 
 /**
- * BPS tree element vs key comparator.
- * Defined in header in order to allow compiler to inline it.
- * @param tuple - tuple to compare.
- * @param key_data - key to compare with.
- * @param def - key definition.
- * @retval 0  if tuple == key in terms of def.
- * @retval <0 if tuple < key in terms of def.
- * @retval >0 if tuple > key in terms of def.
+ * The size of the biggest memtx tree iterator. Used with
+ * mempool_create. This is the size of the block that will be
+ * allocated for each iterator.
  */
-static int
-memtx_tree_compare_key(const struct tuple *tuple,
-		       const struct memtx_tree_key_data *key_data,
-		       struct key_def *def)
-{
-	return tuple_compare_with_key(tuple, key_data->key,
-				      key_data->part_count, def);
-}
+#define MEMTX_TREE_ITERATOR_SIZE (152)
 
-#define BPS_TREE_NAME memtx_tree
+#define bps_tree_elem_t memtx_tree_elem
+#define bps_tree_key_t memtx_tree_key *
+#define bps_tree_arg_t struct key_def *
+#define BPS_TREE_NAME CONCAT3(MEMTX_TREE_NAME, _, tree)
 #define BPS_TREE_BLOCK_SIZE (512)
 #define BPS_TREE_EXTENT_SIZE MEMTX_EXTENT_SIZE
-#define BPS_TREE_COMPARE(a, b, arg) tuple_compare(a, b, arg)
-#define BPS_TREE_COMPARE_KEY(a, b, arg) memtx_tree_compare_key(a, b, arg)
-#define bps_tree_elem_t struct tuple *
-#define bps_tree_key_t struct memtx_tree_key_data *
-#define bps_tree_arg_t struct key_def *
+#define BPS_TREE_COMPARE(a, b, arg) MEMTX_TREE_ELEM_CMP(&a, &b, arg)
+#define BPS_TREE_COMPARE_KEY(a, b, arg) MEMTX_TREE_ELEM_WITH_KEY_CMP(&a, b, arg)
+#define BPS_TREE_NO_DEBUG
 
 #include "salad/bps_tree.h"
 
+#undef bps_tree_elem_t
+#undef bps_tree_key_t
+#undef bps_tree_arg_t
 #undef BPS_TREE_NAME
 #undef BPS_TREE_BLOCK_SIZE
 #undef BPS_TREE_EXTENT_SIZE
 #undef BPS_TREE_COMPARE
 #undef BPS_TREE_COMPARE_KEY
-#undef bps_tree_elem_t
-#undef bps_tree_key_t
-#undef bps_tree_arg_t
+#undef BPS_TREE_NO_DEBUG
+
+#define memtx_tree CONCAT3(MEMTX_TREE_NAME, _, tree)
+#define _tree_api_name(postfix) CONCAT5(MEMTX_TREE_NAME, _, tree, _, postfix)
+#define memtx_tree_iterator _tree_api_name(iterator)
+#define memtx_tree_iterator_is_invalid _tree_api_name(iterator_is_invalid)
+#define memtx_tree_iterator_first _tree_api_name(iterator_first)
+#define memtx_tree_iterator_last _tree_api_name(iterator_last)
+#define memtx_tree_iterator_get_elem _tree_api_name(iterator_get_elem)
+#define memtx_tree_iterator_next _tree_api_name(iterator_next)
+#define memtx_tree_iterator_prev _tree_api_name(iterator_prev)
+#define memtx_tree_iterator_freeze _tree_api_name(iterator_freeze)
+#define memtx_tree_iterator_destroy _tree_api_name(iterator_destroy)
+#define memtx_tree_create _tree_api_name(create)
+#define memtx_tree_build _tree_api_name(build)
+#define memtx_tree_destroy _tree_api_name(destroy)
+#define memtx_tree_find _tree_api_name(find)
+#define memtx_tree_insert _tree_api_name(insert)
+#define memtx_tree_delete _tree_api_name(delete)
+#define memtx_tree_size _tree_api_name(size)
+#define memtx_tree_mem_used _tree_api_name(mem_used)
+#define memtx_tree_random _tree_api_name(random)
+#define memtx_tree_invalid_iterator _tree_api_name(invalid_iterator)
+#define memtx_tree_lower_bound _tree_api_name(lower_bound)
+#define memtx_tree_upper_bound _tree_api_name(upper_bound)
+#define memtx_tree_lower_bound_elem _tree_api_name(lower_bound_elem)
+#define memtx_tree_upper_bound_elem _tree_api_name(upper_bound_elem)
+
+#undef _api_name
+#define _api_name(postfix) CONCAT3(MEMTX_TREE_NAME, _, postfix)
+#define memtx_tree_index _api_name(index)
+#define memtx_tree_qcompare _api_name(qcompare)
+#define tree_iterator _api_name(iterator)
+#define tree_iterator_free _api_name(iterator_free)
+#define tree_iterator_cast _api_name(iterator_cast)
+#define tree_iterator_dummie _api_name(iterator_dummie)
+#define tree_iterator_next _api_name(iterator_next)
+#define tree_iterator_prev _api_name(iterator_prev)
+#define tree_iterator_next_equal _api_name(iterator_next_equal)
+#define tree_iterator_prev_equal _api_name(iterator_prev_equal)
+#define tree_iterator_set_next_method _api_name(iterator_set_next_method)
+#define tree_iterator_start _api_name(iterator_start)
+#define memtx_tree_index_cmp_def _api_name(index_cmp_def)
+#define memtx_tree_index_free _api_name(index_free)
+#define memtx_tree_index_gc_run _api_name(index_gc_run)
+#define memtx_tree_index_gc_free _api_name(index_gc_free)
+#define memtx_tree_index_gc_vtab _api_name(index_gc_vtab)
+#define memtx_tree_index_destroy _api_name(index_destroy)
+#define memtx_tree_index_update_def _api_name(index_update_def)
+#define memtx_tree_index_depends_on_pk _api_name(index_depends_on_pk)
+#define memtx_tree_index_size _api_name(index_size)
+#define memtx_tree_index_bsize _api_name(index_bsize)
+#define memtx_tree_index_random _api_name(index_random)
+#define memtx_tree_index_count _api_name(index_count)
+#define memtx_tree_index_get _api_name(index_get)
+#define memtx_tree_index_insert_tuple _api_name(index_insert_tuple)
+#define memtx_tree_index_delete_tuple _api_name(index_delete_tuple)
+#define memtx_tree_index_replace _api_name(index_replace)
+#define memtx_tree_index_create_iterator _api_name(index_create_iterator)
+#define memtx_tree_index_begin_build _api_name(index_begin_build)
+#define memtx_tree_index_build_next _api_name(index_build_next)
+#define memtx_tree_index_reserve _api_name(index_reserve)
+#define memtx_tree_index_end_build _api_name(index_end_build)
+#define tree_snapshot_iterator _api_name(snapshot_iterator)
+#define tree_snapshot_iterator_free _api_name(snapshot_iterator_free)
+#define tree_snapshot_iterator_next _api_name(snapshot_iterator_next)
+#define memtx_tree_index_create_snapshot_iterator\
+	_api_name(index_create_snapshot_iterator)
+#define memtx_tree_index_vtab _api_name(index_vtab)
+#define memtx_tree_index_new _api_name(index_new)
 
 struct memtx_tree_index {
 	struct index base;
-	struct memtx_tree tree;
-	struct tuple **build_array;
+	memtx_tree_elem *build_array;
 	size_t build_array_size, build_array_alloc_size;
 	struct memtx_gc_task gc_task;
+	struct memtx_tree tree;
 	struct memtx_tree_iterator gc_iterator;
 };
 
@@ -102,8 +186,8 @@ struct memtx_tree_index {
 static int
 memtx_tree_qcompare(const void* a, const void *b, void *c)
 {
-	return tuple_compare(*(struct tuple **)a,
-		*(struct tuple **)b, (struct key_def *)c);
+	return MEMTX_TREE_ELEM_CMP((memtx_tree_elem *)a,
+				   (memtx_tree_elem *)b, c);
 }
 
 /* {{{ MemtxTree Iterators ****************************************/
@@ -113,17 +197,21 @@ struct tree_iterator {
 	struct index_def *index_def;
 	struct memtx_tree_iterator tree_iterator;
 	enum iterator_type type;
-	struct memtx_tree_key_data key_data;
-	struct tuple *current_tuple;
+	memtx_tree_key key_data;
+	memtx_tree_elem current;
 	/** Memory pool the iterator was allocated from. */
 	struct mempool *pool;
 };
 
+static_assert(sizeof(struct tree_iterator) <= MEMTX_TREE_ITERATOR_SIZE,
+	      "tree_iterator must be less or equal than "
+	      "MEMTX_TREE_ITERATOR_SIZE");
+
 static void
 tree_iterator_free(struct iterator *iterator);
 
 static inline struct tree_iterator *
-tree_iterator(struct iterator *it)
+tree_iterator_cast(struct iterator *it)
 {
 	assert(it->free == tree_iterator_free);
 	return (struct tree_iterator *) it;
@@ -132,9 +220,10 @@ tree_iterator(struct iterator *it)
 static void
 tree_iterator_free(struct iterator *iterator)
 {
-	struct tree_iterator *it = tree_iterator(iterator);
-	if (it->current_tuple != NULL)
-		tuple_unref(it->current_tuple);
+	struct tree_iterator *it = tree_iterator_cast(iterator);
+	struct tuple *tuple = MEMTX_TREE_ELEM_GET(&it->current);
+	if (tuple != NULL)
+		tuple_unref(tuple);
 	mempool_free(it->pool, it);
 }
 
@@ -149,25 +238,28 @@ tree_iterator_dummie(struct iterator *iterator, struct tuple **ret)
 static int
 tree_iterator_next(struct iterator *iterator, struct tuple **ret)
 {
-	struct tuple **res;
-	struct tree_iterator *it = tree_iterator(iterator);
-	assert(it->current_tuple != NULL);
-	struct tuple **check = memtx_tree_iterator_get_elem(it->tree, &it->tree_iterator);
-	if (check == NULL || *check != it->current_tuple)
+	struct tree_iterator *it = tree_iterator_cast(iterator);
+	assert(MEMTX_TREE_ELEM_GET(&it->current) != NULL);
+	memtx_tree_elem *check =
+		memtx_tree_iterator_get_elem(it->tree, &it->tree_iterator);
+	if (check == NULL ||
+	    MEMTX_TREE_ELEM_GET(check) != MEMTX_TREE_ELEM_GET(&it->current)) {
 		it->tree_iterator =
-			memtx_tree_upper_bound_elem(it->tree, it->current_tuple,
-						    NULL);
-	else
+			memtx_tree_upper_bound_elem(it->tree, it->current, NULL);
+	} else {
 		memtx_tree_iterator_next(it->tree, &it->tree_iterator);
-	tuple_unref(it->current_tuple);
-	it->current_tuple = NULL;
-	res = memtx_tree_iterator_get_elem(it->tree, &it->tree_iterator);
+	}
+	tuple_unref(MEMTX_TREE_ELEM_GET(&it->current));
+	memtx_tree_elem *res =
+		memtx_tree_iterator_get_elem(it->tree, &it->tree_iterator);
 	if (res == NULL) {
 		iterator->next = tree_iterator_dummie;
+		memset(&it->current, 0, sizeof(it->current));
 		*ret = NULL;
 	} else {
-		*ret = it->current_tuple = *res;
-		tuple_ref(it->current_tuple);
+		*ret = MEMTX_TREE_ELEM_GET(res);
+		tuple_ref(*ret);
+		it->current = *res;
 	}
 	return 0;
 }
@@ -175,23 +267,27 @@ tree_iterator_next(struct iterator *iterator, struct tuple **ret)
 static int
 tree_iterator_prev(struct iterator *iterator, struct tuple **ret)
 {
-	struct tree_iterator *it = tree_iterator(iterator);
-	assert(it->current_tuple != NULL);
-	struct tuple **check = memtx_tree_iterator_get_elem(it->tree, &it->tree_iterator);
-	if (check == NULL || *check != it->current_tuple)
+	struct tree_iterator *it = tree_iterator_cast(iterator);
+	assert(MEMTX_TREE_ELEM_GET(&it->current) != NULL);
+	memtx_tree_elem *check =
+		memtx_tree_iterator_get_elem(it->tree, &it->tree_iterator);
+	if (check == NULL ||
+	    MEMTX_TREE_ELEM_GET(check) != MEMTX_TREE_ELEM_GET(&it->current)) {
 		it->tree_iterator =
-			memtx_tree_lower_bound_elem(it->tree, it->current_tuple,
-						    NULL);
+			memtx_tree_lower_bound_elem(it->tree, it->current, NULL);
+	}
 	memtx_tree_iterator_prev(it->tree, &it->tree_iterator);
-	tuple_unref(it->current_tuple);
-	it->current_tuple = NULL;
-	struct tuple **res = memtx_tree_iterator_get_elem(it->tree, &it->tree_iterator);
+	tuple_unref(MEMTX_TREE_ELEM_GET(&it->current));
+	memtx_tree_elem *res =
+		memtx_tree_iterator_get_elem(it->tree, &it->tree_iterator);
 	if (!res) {
 		iterator->next = tree_iterator_dummie;
+		memset(&it->current, 0, sizeof(it->current));
 		*ret = NULL;
 	} else {
-		*ret = it->current_tuple = *res;
-		tuple_ref(it->current_tuple);
+		*ret = MEMTX_TREE_ELEM_GET(res);
+		tuple_ref(*ret);
+		it->current = *res;
 	}
 	return 0;
 }
@@ -199,28 +295,31 @@ tree_iterator_prev(struct iterator *iterator, struct tuple **ret)
 static int
 tree_iterator_next_equal(struct iterator *iterator, struct tuple **ret)
 {
-	struct tree_iterator *it = tree_iterator(iterator);
-	assert(it->current_tuple != NULL);
-	struct tuple **check = memtx_tree_iterator_get_elem(it->tree,
-						&it->tree_iterator);
-	if (check == NULL || *check != it->current_tuple)
+	struct tree_iterator *it = tree_iterator_cast(iterator);
+	assert(MEMTX_TREE_ELEM_GET(&it->current) != NULL);
+	memtx_tree_elem *check =
+		memtx_tree_iterator_get_elem(it->tree, &it->tree_iterator);
+	if (check == NULL ||
+	    MEMTX_TREE_ELEM_GET(check) != MEMTX_TREE_ELEM_GET(&it->current)) {
 		it->tree_iterator =
-			memtx_tree_upper_bound_elem(it->tree, it->current_tuple,
-						    NULL);
-	else
+			memtx_tree_upper_bound_elem(it->tree, it->current, NULL);
+	} else {
 		memtx_tree_iterator_next(it->tree, &it->tree_iterator);
-	tuple_unref(it->current_tuple);
-	it->current_tuple = NULL;
-	struct tuple **res = memtx_tree_iterator_get_elem(it->tree,
-						&it->tree_iterator);
+	}
+	tuple_unref(MEMTX_TREE_ELEM_GET(&it->current));
+	memtx_tree_elem *res =
+		memtx_tree_iterator_get_elem(it->tree, &it->tree_iterator);
 	/* Use user key def to save a few loops. */
-	if (!res || memtx_tree_compare_key(*res, &it->key_data,
-					   it->index_def->key_def) != 0) {
+	if (!res ||
+	    MEMTX_TREE_ELEM_WITH_KEY_CMP(res, &it->key_data,
+					 it->index_def->key_def) != 0) {
 		iterator->next = tree_iterator_dummie;
+		memset(&it->current, 0, sizeof(it->current));
 		*ret = NULL;
 	} else {
-		*ret = it->current_tuple = *res;
-		tuple_ref(it->current_tuple);
+		*ret = MEMTX_TREE_ELEM_GET(res);
+		tuple_ref(*ret);
+		it->current = *res;
 	}
 	return 0;
 }
@@ -228,27 +327,30 @@ tree_iterator_next_equal(struct iterator *iterator, struct tuple **ret)
 static int
 tree_iterator_prev_equal(struct iterator *iterator, struct tuple **ret)
 {
-	struct tree_iterator *it = tree_iterator(iterator);
-	assert(it->current_tuple != NULL);
-	struct tuple **check = memtx_tree_iterator_get_elem(it->tree,
-						&it->tree_iterator);
-	if (check == NULL || *check != it->current_tuple)
+	struct tree_iterator *it = tree_iterator_cast(iterator);
+	assert(MEMTX_TREE_ELEM_GET(&it->current) != NULL);
+	memtx_tree_elem *check =
+		memtx_tree_iterator_get_elem(it->tree, &it->tree_iterator);
+	if (check == NULL ||
+	    MEMTX_TREE_ELEM_GET(check) != MEMTX_TREE_ELEM_GET(&it->current)) {
 		it->tree_iterator =
-			memtx_tree_lower_bound_elem(it->tree, it->current_tuple,
-						    NULL);
+			memtx_tree_lower_bound_elem(it->tree, it->current, NULL);
+	}
 	memtx_tree_iterator_prev(it->tree, &it->tree_iterator);
-	tuple_unref(it->current_tuple);
-	it->current_tuple = NULL;
-	struct tuple **res = memtx_tree_iterator_get_elem(it->tree,
-						&it->tree_iterator);
+	tuple_unref(MEMTX_TREE_ELEM_GET(&it->current));
+	memtx_tree_elem *res =
+		memtx_tree_iterator_get_elem(it->tree, &it->tree_iterator);
 	/* Use user key def to save a few loops. */
-	if (!res || memtx_tree_compare_key(*res, &it->key_data,
-					   it->index_def->key_def) != 0) {
+	if (!res ||
+	    MEMTX_TREE_ELEM_WITH_KEY_CMP(res, &it->key_data,
+					 it->index_def->key_def) != 0) {
 		iterator->next = tree_iterator_dummie;
+		memset(&it->current, 0, sizeof(it->current));
 		*ret = NULL;
 	} else {
-		*ret = it->current_tuple = *res;
-		tuple_ref(it->current_tuple);
+		*ret = MEMTX_TREE_ELEM_GET(res);
+		tuple_ref(*ret);
+		it->current = *res;
 	}
 	return 0;
 }
@@ -256,7 +358,7 @@ tree_iterator_prev_equal(struct iterator *iterator, struct tuple **ret)
 static void
 tree_iterator_set_next_method(struct tree_iterator *it)
 {
-	assert(it->current_tuple != NULL);
+	assert(MEMTX_TREE_ELEM_GET(&it->current) != NULL);
 	switch (it->type) {
 	case ITER_EQ:
 		it->base.next = tree_iterator_next_equal;
@@ -285,13 +387,15 @@ static int
 tree_iterator_start(struct iterator *iterator, struct tuple **ret)
 {
 	*ret = NULL;
-	struct tree_iterator *it = tree_iterator(iterator);
+	struct tree_iterator *it = tree_iterator_cast(iterator);
 	it->base.next = tree_iterator_dummie;
 	const struct memtx_tree *tree = it->tree;
 	enum iterator_type type = it->type;
 	bool exact = false;
-	assert(it->current_tuple == NULL);
-	if (it->key_data.key == 0) {
+	assert(MEMTX_TREE_ELEM_GET(&it->current) == NULL);
+	uint32_t part_count;
+	const char *key = MEMTX_TREE_KEY_GET(&it->key_data, &part_count);
+	if (key == NULL) {
 		if (iterator_type_is_reverse(it->type))
 			it->tree_iterator = memtx_tree_iterator_last(tree);
 		else
@@ -327,12 +431,13 @@ tree_iterator_start(struct iterator *iterator, struct tuple **ret)
 		}
 	}
 
-	struct tuple **res = memtx_tree_iterator_get_elem(it->tree,
-						&it->tree_iterator);
+	memtx_tree_elem *res =
+		memtx_tree_iterator_get_elem(it->tree, &it->tree_iterator);
 	if (!res)
 		return 0;
-	*ret = it->current_tuple = *res;
-	tuple_ref(it->current_tuple);
+	*ret = MEMTX_TREE_ELEM_GET(res);
+	tuple_ref(*ret);
+	it->current = *res;
 	tree_iterator_set_next_method(it);
 	return 0;
 }
@@ -386,7 +491,8 @@ memtx_tree_index_gc_run(struct memtx_gc_task *task, bool *done)
 
 	unsigned int loops = 0;
 	while (!memtx_tree_iterator_is_invalid(itr)) {
-		struct tuple *tuple = *memtx_tree_iterator_get_elem(tree, itr);
+		memtx_tree_elem *res = memtx_tree_iterator_get_elem(tree, itr);
+		struct tuple *tuple = MEMTX_TREE_ELEM_GET(res);;
 		memtx_tree_iterator_next(tree, itr);
 		tuple_unref(tuple);
 		if (++loops >= YIELD_LOOPS) {
@@ -466,8 +572,8 @@ static int
 memtx_tree_index_random(struct index *base, uint32_t rnd, struct tuple **result)
 {
 	struct memtx_tree_index *index = (struct memtx_tree_index *)base;
-	struct tuple **res = memtx_tree_random(&index->tree, rnd);
-	*result = res != NULL ? *res : NULL;
+	memtx_tree_elem *res = memtx_tree_random(&index->tree, rnd);
+	*result = res != NULL ? MEMTX_TREE_ELEM_GET(res) : NULL;
 	return 0;
 }
 
@@ -487,26 +593,50 @@ memtx_tree_index_get(struct index *base, const char *key,
 	assert(base->def->opts.is_unique &&
 	       part_count == base->def->key_def->part_count);
 	struct memtx_tree_index *index = (struct memtx_tree_index *)base;
-	struct memtx_tree_key_data key_data;
-	key_data.key = key;
-	key_data.part_count = part_count;
-	struct tuple **res = memtx_tree_find(&index->tree, &key_data);
-	*result = res != NULL ? *res : NULL;
+	memtx_tree_key key_data;
+	struct key_def *cmp_def = memtx_tree_index_cmp_def(index);
+	MEMTX_TREE_KEY_SET(&key_data, key, part_count, cmp_def);
+	memtx_tree_elem *res = memtx_tree_find(&index->tree, &key_data);
+	*result = res != NULL ? MEMTX_TREE_ELEM_GET(res) : NULL;
 	return 0;
 }
 
+static int
+memtx_tree_index_insert_tuple(struct index *base, struct tuple *tuple,
+			      struct tuple **replaced)
+{
+	struct memtx_tree_index *index = (struct memtx_tree_index *)base;
+	memtx_tree_elem data;
+	MEMTX_TREE_ELEM_SET(&data, tuple, index->tree.arg);
+	memtx_tree_elem data_replaced;
+	memset(&data_replaced, 0, sizeof(data_replaced));
+	int rc = memtx_tree_insert(&index->tree, data, &data_replaced);
+	if (replaced != NULL)
+		*replaced = MEMTX_TREE_ELEM_GET(&data_replaced);
+	return rc;
+}
+
+static void
+memtx_tree_index_delete_tuple(struct index *base, struct tuple *tuple)
+{
+	struct memtx_tree_index *index = (struct memtx_tree_index *)base;
+	memtx_tree_elem data;
+	MEMTX_TREE_ELEM_SET(&data, tuple, index->tree.arg);
+	memtx_tree_delete(&index->tree, data);
+}
+
 static int
 memtx_tree_index_replace(struct index *base, struct tuple *old_tuple,
 			 struct tuple *new_tuple, enum dup_replace_mode mode,
 			 struct tuple **result)
 {
-	struct memtx_tree_index *index = (struct memtx_tree_index *)base;
 	if (new_tuple) {
 		struct tuple *dup_tuple = NULL;
 
 		/* Try to optimistically replace the new_tuple. */
-		int tree_res = memtx_tree_insert(&index->tree,
-						 new_tuple, &dup_tuple);
+		int tree_res =
+			memtx_tree_index_insert_tuple(base, new_tuple,
+						      &dup_tuple);
 		if (tree_res) {
 			diag_set(OutOfMemory, MEMTX_EXTENT_SIZE,
 				 "memtx_tree_index", "replace");
@@ -516,9 +646,9 @@ memtx_tree_index_replace(struct index *base, struct tuple *old_tuple,
 		uint32_t errcode = replace_check_dup(old_tuple,
 						     dup_tuple, mode);
 		if (errcode) {
-			memtx_tree_delete(&index->tree, new_tuple);
+			memtx_tree_index_delete_tuple(base, new_tuple);
 			if (dup_tuple)
-				memtx_tree_insert(&index->tree, dup_tuple, 0);
+				memtx_tree_index_insert_tuple(base, dup_tuple, 0);
 			struct space *sp = space_cache_find(base->def->space_id);
 			if (sp != NULL)
 				diag_set(ClientError, errcode, base->def->name,
@@ -530,9 +660,8 @@ memtx_tree_index_replace(struct index *base, struct tuple *old_tuple,
 			return 0;
 		}
 	}
-	if (old_tuple) {
-		memtx_tree_delete(&index->tree, old_tuple);
-	}
+	if (old_tuple)
+		memtx_tree_index_delete_tuple(base, old_tuple);
 	*result = old_tuple;
 	return 0;
 }
@@ -571,12 +700,12 @@ memtx_tree_index_create_iterator(struct index *base, enum iterator_type type,
 	it->base.next = tree_iterator_start;
 	it->base.free = tree_iterator_free;
 	it->type = type;
-	it->key_data.key = key;
-	it->key_data.part_count = part_count;
+	struct key_def *cmp_def = memtx_tree_index_cmp_def(index);
+	MEMTX_TREE_KEY_SET(&it->key_data, key, part_count, cmp_def);
 	it->index_def = base->def;
 	it->tree = &index->tree;
 	it->tree_iterator = memtx_tree_invalid_iterator();
-	it->current_tuple = NULL;
+	memset(&it->current, 0, sizeof(it->current));
 	return (struct iterator *)it;
 }
 
@@ -594,8 +723,8 @@ memtx_tree_index_reserve(struct index *base, uint32_t size_hint)
 	struct memtx_tree_index *index = (struct memtx_tree_index *)base;
 	if (size_hint < index->build_array_alloc_size)
 		return 0;
-	struct tuple **tmp = (struct tuple **)realloc(index->build_array,
-						      size_hint * sizeof(*tmp));
+	memtx_tree_elem *tmp =
+		realloc(index->build_array, size_hint * sizeof(*tmp));
 	if (tmp == NULL) {
 		diag_set(OutOfMemory, size_hint * sizeof(*tmp),
 			 "memtx_tree_index", "reserve");
@@ -611,20 +740,20 @@ memtx_tree_index_build_next(struct index *base, struct tuple *tuple)
 {
 	struct memtx_tree_index *index = (struct memtx_tree_index *)base;
 	if (index->build_array == NULL) {
-		index->build_array = (struct tuple **)malloc(MEMTX_EXTENT_SIZE);
+		index->build_array = (memtx_tree_elem *)malloc(MEMTX_EXTENT_SIZE);
 		if (index->build_array == NULL) {
 			diag_set(OutOfMemory, MEMTX_EXTENT_SIZE,
 				 "memtx_tree_index", "build_next");
 			return -1;
 		}
 		index->build_array_alloc_size =
-			MEMTX_EXTENT_SIZE / sizeof(struct tuple*);
+			MEMTX_EXTENT_SIZE / sizeof(index->build_array[0]);
 	}
 	assert(index->build_array_size <= index->build_array_alloc_size);
 	if (index->build_array_size == index->build_array_alloc_size) {
 		index->build_array_alloc_size = index->build_array_alloc_size +
 					index->build_array_alloc_size / 2;
-		struct tuple **tmp = (struct tuple **)
+		memtx_tree_elem *tmp =
 			realloc(index->build_array,
 				index->build_array_alloc_size * sizeof(*tmp));
 		if (tmp == NULL) {
@@ -634,7 +763,8 @@ memtx_tree_index_build_next(struct index *base, struct tuple *tuple)
 		}
 		index->build_array = tmp;
 	}
-	index->build_array[index->build_array_size++] = tuple;
+	MEMTX_TREE_ELEM_SET(&index->build_array[index->build_array_size++],
+			    tuple, memtx_tree_index_cmp_def(index));
 	return 0;
 }
 
@@ -644,10 +774,9 @@ memtx_tree_index_end_build(struct index *base)
 	struct memtx_tree_index *index = (struct memtx_tree_index *)base;
 	struct key_def *cmp_def = memtx_tree_index_cmp_def(index);
 	qsort_arg(index->build_array, index->build_array_size,
-		  sizeof(struct tuple *),
-		  memtx_tree_qcompare, cmp_def);
+		  sizeof(index->build_array[0]), memtx_tree_qcompare, cmp_def);
 	memtx_tree_build(&index->tree, index->build_array,
-			 index->build_array_size);
+		       index->build_array_size);
 
 	free(index->build_array);
 	index->build_array = NULL;
@@ -678,12 +807,12 @@ tree_snapshot_iterator_next(struct snapshot_iterator *iterator, uint32_t *size)
 	assert(iterator->free == tree_snapshot_iterator_free);
 	struct tree_snapshot_iterator *it =
 		(struct tree_snapshot_iterator *)iterator;
-	struct tuple **res = memtx_tree_iterator_get_elem(it->tree,
-						&it->tree_iterator);
+	memtx_tree_elem *res =
+		memtx_tree_iterator_get_elem(it->tree, &it->tree_iterator);
 	if (res == NULL)
 		return NULL;
 	memtx_tree_iterator_next(it->tree, &it->tree_iterator);
-	return tuple_data_range(*res, size);
+	return tuple_data_range(MEMTX_TREE_ELEM_GET(res), size);
 }
 
 /**
@@ -746,7 +875,7 @@ memtx_tree_index_new(struct memtx_engine *memtx, struct index_def *def)
 {
 	if (!mempool_is_initialized(&memtx->tree_iterator_pool)) {
 		mempool_create(&memtx->tree_iterator_pool, cord_slab_cache(),
-			       sizeof(struct tree_iterator));
+			       MEMTX_TREE_ITERATOR_SIZE);
 	}
 
 	struct memtx_tree_index *index =
@@ -767,3 +896,74 @@ memtx_tree_index_new(struct memtx_engine *memtx, struct index_def *def)
 			  memtx_index_extent_free, memtx);
 	return &index->base;
 }
+
+#undef _tree_api_name
+#undef memtx_tree
+#undef memtx_tree_iterator
+#undef memtx_tree_iterator_is_invalid
+#undef memtx_tree_iterator_first
+#undef memtx_tree_iterator_last
+#undef memtx_tree_iterator_get_elem
+#undef memtx_tree_iterator_next
+#undef memtx_tree_iterator_prev
+#undef memtx_tree_iterator_freeze
+#undef memtx_tree_iterator_destroy
+#undef memtx_tree_create
+#undef memtx_tree_build
+#undef memtx_tree_destroy
+#undef memtx_tree_find
+#undef memtx_tree_insert
+#undef memtx_tree_delete
+#undef memtx_tree_size
+#undef memtx_tree_mem_used
+#undef memtx_tree_random
+#undef memtx_tree_invalid_iterator
+#undef memtx_tree_lower_bound
+#undef memtx_tree_upper_bound
+#undef memtx_tree_lower_bound_elem
+#undef memtx_tree_upper_bound_elem
+
+#undef _api_name
+#undef memtx_tree_index
+#undef memtx_tree_qcompare
+#undef tree_iterator
+#undef tree_iterator_free
+#undef tree_iterator_cast
+#undef tree_iterator_dummie
+#undef tree_iterator_next
+#undef tree_iterator_prev
+#undef tree_iterator_next_equal
+#undef tree_iterator_prev_equal
+#undef tree_iterator_set_next_method
+#undef tree_iterator_start
+#undef memtx_tree_index_cmp_def
+#undef memtx_tree_index_free
+#undef memtx_tree_index_gc_run
+#undef memtx_tree_index_gc_free
+#undef memtx_tree_index_gc_vtab
+#undef memtx_tree_index_destroy
+#undef memtx_tree_index_update_def
+#undef memtx_tree_index_depends_on_pk
+#undef memtx_tree_index_size
+#undef memtx_tree_index_bsize
+#undef memtx_tree_index_random
+#undef memtx_tree_index_count
+#undef memtx_tree_index_get
+#undef memtx_tree_index_insert_tuple
+#undef memtx_tree_index_delete_tuple
+#undef memtx_tree_index_replace
+#undef memtx_tree_index_create_iterator
+#undef memtx_tree_index_begin_build
+#undef memtx_tree_index_build_next
+#undef memtx_tree_index_reserve
+#undef memtx_tree_index_end_build
+#undef tree_snapshot_iterator
+#undef tree_snapshot_iterator_free
+#undef tree_snapshot_iterator_next
+#undef tree_index_create_snapshot_iterator
+#undef memtx_tree_index_vtab
+#undef memtx_tree_index_new
+
+#if defined(__cplusplus)
+} /* extern "C" */
+#endif /* defined(__cplusplus) */
diff --git a/src/box/memtx_tree_decl.c b/src/box/memtx_tree_decl.c
new file mode 100644
index 000000000..03e0e0ed7
--- /dev/null
+++ b/src/box/memtx_tree_decl.c
@@ -0,0 +1,84 @@
+/*
+ * Copyright 2010-2019, Tarantool AUTHORS, please see AUTHORS file.
+ *
+ * Redistribution and use in source and binary forms, with or
+ * without modification, are permitted provided that the following
+ * conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above
+ *    copyright notice, this list of conditions and the
+ *    following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above
+ *    copyright notice, this list of conditions and the following
+ *    disclaimer in the documentation and/or other materials
+ *    provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY <COPYRIGHT HOLDER> ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
+ * <COPYRIGHT HOLDER> OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
+ * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
+ * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+ * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
+ * THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+#include <stdbool.h>
+#include <stdint.h>
+#include "tuple_compare.h"
+#include "memtx_tree.h"
+
+/* {{{ Memtx tree of tuples class. ******************************/
+
+/** Struct that is used as a key in BPS tree definition. */
+struct memtx_tuple_tree_key_data {
+	/** Sequence of msgpacked search fields. */
+	const char *key;
+	/** Number of msgpacked search fields. */
+	uint32_t part_count;
+};
+
+#define MEMTX_TREE_NAME memtx_tuple_tree
+#define memtx_tree_elem struct tuple *
+#define memtx_tree_key struct memtx_tuple_tree_key_data
+#define MEMTX_TREE_ELEM_CMP(elem_a_ptr, elem_b_ptr, key_def)			\
+	tuple_compare(*elem_a_ptr, *elem_b_ptr, key_def)
+#define MEMTX_TREE_ELEM_WITH_KEY_CMP(elem_ptr, key_ptr, key_def)		\
+	tuple_compare_with_key(*elem_ptr, (key_ptr)->key,			\
+			       (key_ptr)->part_count, key_def)
+#define MEMTX_TREE_ELEM_SET(elem_ptr, tuple, key_def)				\
+	({(void)key_def; *elem_ptr = tuple;})
+#define MEMTX_TREE_KEY_SET(key_ptr, key_val, part_count_val, key_def)		\
+	({(void)key_def; (key_ptr)->key = key_val;				\
+	 (key_ptr)->part_count = part_count_val;})
+#define MEMTX_TREE_ELEM_GET(elem_ptr) (*(elem_ptr))
+#define MEMTX_TREE_KEY_GET(key_ptr, part_count_ptr)				\
+	({*part_count_ptr = (key_ptr)->part_count; (key_ptr)->key;})
+
+#include "memtx_tree.c"
+
+#undef memtx_tree_key
+#undef memtx_tree_elem
+#undef MEMTX_TREE_KEY_GET
+#undef MEMTX_TREE_ELEM_GET
+#undef MEMTX_TREE_KEY_SET
+#undef MEMTX_TREE_ELEM_SET
+#undef MEMTX_TREE_ELEM_WITH_KEY_CMP
+#undef MEMTX_TREE_ELEM_CMP
+#undef MEMTX_TREE_ELEM_EQUAL
+#undef memtx_tree_key
+#undef memtx_tree_elem
+#undef MEMTX_TREE_NAME
+
+/* }}} */
+
+struct index *
+memtx_tree_index_new(struct memtx_engine *memtx, struct index_def *def)
+{
+	return memtx_tuple_tree_index_new(memtx, def);
+}
-- 
2.20.1

[PATCH v2 3/4] box: rename memtx_tree.c to memtx_tree_impl.h

[Kirill Shcherbatov]

File meta_tree.c that implements the template class memtx_tree,
renamed to memes_tree_impl.h due to the fact that the inclusion
of code in header files is more common.

Needed for #3961
---
 src/box/memtx_tree_decl.c                   | 2 +-
 src/box/{memtx_tree.c => memtx_tree_impl.h} | 0
 2 files changed, 1 insertion(+), 1 deletion(-)
 rename src/box/{memtx_tree.c => memtx_tree_impl.h} (100%)

diff --git a/src/box/memtx_tree_decl.c b/src/box/memtx_tree_decl.c
index 03e0e0ed7..084a0594f 100644
--- a/src/box/memtx_tree_decl.c
+++ b/src/box/memtx_tree_decl.c
@@ -60,7 +60,7 @@ struct memtx_tuple_tree_key_data {
 #define MEMTX_TREE_KEY_GET(key_ptr, part_count_ptr)				\
 	({*part_count_ptr = (key_ptr)->part_count; (key_ptr)->key;})
 
-#include "memtx_tree.c"
+#include "memtx_tree_impl.h"
 
 #undef memtx_tree_key
 #undef memtx_tree_elem
diff --git a/src/box/memtx_tree.c b/src/box/memtx_tree_impl.h
similarity index 100%
rename from src/box/memtx_tree.c
rename to src/box/memtx_tree_impl.h
-- 
2.20.1

[PATCH v2 4/4] box: introduce tuple compare hint for string index

[Kirill Shcherbatov]

From: Alexandr Lyapunov <aleks@tarantool.org>

Implement functions for retrieving tuple hints for a particular
key_def. Hint is an integer that can be used for tuple comparison
optimization: if a hint of one tuple is less than a hint of another
then the first tuple is definitely less than the second; only if
hints are equal tuple_compare must be called for getting comparison
result.

Hints are calculated using only the first part of key_def.

Hints are only useful when:
 * they are precalculated and stored along with the tuple;
calculation is not cheap (cheaper than tuple_compare btw) but
precalculated hints allow to compare tuples without even fetching
tuple data.
 * first part of key_def is 'string'(for now)
 * since hint is calculated using only the first part of key_def
(and only first several characters if it is a string) this part
must be different with high probability for every tuple pair.

Part of #3961
---
 src/box/key_def.c         |   1 +
 src/box/key_def.h         |  44 ++++++++++++++
 src/box/memtx_tree_decl.c | 123 ++++++++++++++++++++++++++++++++++++++
 src/box/tuple_compare.cc  | 101 +++++++++++++++++++++++++++++++
 src/box/tuple_compare.h   |   7 +++
 src/coll.c                |  45 ++++++++++++++
 src/coll.h                |   4 ++
 7 files changed, 325 insertions(+)

diff --git a/src/box/key_def.c b/src/box/key_def.c
index 9411ade39..ceca1ebee 100644
--- a/src/box/key_def.c
+++ b/src/box/key_def.c
@@ -135,6 +135,7 @@ key_def_set_cmp(struct key_def *def)
 	def->tuple_compare_with_key = tuple_compare_with_key_create(def);
 	tuple_hash_func_set(def);
 	tuple_extract_key_set(def);
+	tuple_hint_set(def);
 }
 
 static void
diff --git a/src/box/key_def.h b/src/box/key_def.h
index bf3e63b6d..a2a0bbecb 100644
--- a/src/box/key_def.h
+++ b/src/box/key_def.h
@@ -153,6 +153,13 @@ typedef uint32_t (*tuple_hash_t)(const struct tuple *tuple,
 typedef uint32_t (*key_hash_t)(const char *key,
 				struct key_def *key_def);
 
+/** @copydoc tuple_hint() */
+typedef uint64_t (*tuple_hint_t)(const struct tuple *tuple,
+				 struct key_def *key_def);
+
+/** @copydoc key_hint() */
+typedef uint64_t (*key_hint_t)(const char *key, struct key_def *key_def);
+
 /* Definition of a multipart key. */
 struct key_def {
 	/** @see tuple_compare() */
@@ -167,6 +174,10 @@ struct key_def {
 	tuple_hash_t tuple_hash;
 	/** @see key_hash() */
 	key_hash_t key_hash;
+	/** @see tuple_hint() */
+	tuple_hint_t tuple_hint;
+	/** @see key_hint() */
+	key_hint_t key_hint;
 	/**
 	 * Minimal part count which always is unique. For example,
 	 * if a secondary index is unique, then
@@ -551,6 +562,39 @@ tuple_compare_with_key(const struct tuple *tuple, const char *key,
 	return key_def->tuple_compare_with_key(tuple, key, part_count, key_def);
 }
 
+/**
+ * Get a comparison hint of a tuple.
+ * Hint is such a function h(tuple) in terms of particular key_def that
+ * has follows rules:
+ * if h(t1) < h(t2) then t1 < t2;
+ * if h(t1) > h(t2) then t1 > t2;
+ * if t1 == t2 then h(t1) == h(t2);
+ * These rules means that instead of direct tuple vs tuple (or tuple vs key)
+ * comparison one may compare theirs hints first; and only if theirs hints
+ * are equal compare the tuples themselves.
+ * @param tuple - tuple to get hint of.
+ * @param key_def - key_def that defines which comparison is used.
+ * @return the hint.
+ */
+static inline uint64_t
+tuple_hint(const struct tuple *tuple, struct key_def *key_def)
+{
+	return key_def->tuple_hint(tuple, key_def);
+}
+
+/**
+ * Get a comparison hint of a key.
+ * @See tuple_hint for hint term definition.
+ * @param key - key to get hint of.
+ * @param key_def - key_def that defines which comparison is used.
+ * @return the hint.
+ */
+static inline uint64_t
+key_hint(const char *key, struct key_def *key_def)
+{
+	return key_def->key_hint(key, key_def);
+}
+
 #if defined(__cplusplus)
 } /* extern "C" */
 #endif /* defined(__cplusplus) */
diff --git a/src/box/memtx_tree_decl.c b/src/box/memtx_tree_decl.c
index 084a0594f..264241832 100644
--- a/src/box/memtx_tree_decl.c
+++ b/src/box/memtx_tree_decl.c
@@ -77,8 +77,131 @@ struct memtx_tuple_tree_key_data {
 
 /* }}} */
 
+/* {{{ Memtx hinted and hint_only tree class. *******************/
+
+/**
+ * Struct that is used as a key in BPS tree definition in
+ * memtx_hint_only_tree and memtx_hinted_tree.
+*/
+struct memtx_hinted_tree_key_data {
+	/** Sequence of msgpacked search fields. */
+	const char *key;
+	/** Number of msgpacked search fields. */
+	uint32_t part_count;
+	/**
+	 * Compare hint. Is calculated automatically on 'set'
+	 * operation with memtx_hinted_tree_key_data_set().
+	 */
+	uint64_t hint;
+};
+
+/**
+ * Struct that is used as a key in BPS tree definition in
+ * memtx_hint_only_tree and memtx_hinted_tree.
+ */
+struct memtx_hinted_tree_data {
+	/** Tuple this node is representing. */
+	struct tuple *tuple;
+	/**
+	 * Compare hint. Is calculated automatically on 'set'
+	 * operation with memtx_hinted_tree_data_set().
+	 */
+	uint64_t hint;
+};
+
+/**
+ * Compare memtx_hinted_tree records.
+ */
+static int
+memtx_hinted_tree_data_cmp(struct memtx_hinted_tree_data *a,
+			   struct memtx_hinted_tree_data *b,
+			   struct key_def *key_def)
+{
+	if (a->hint != b->hint)
+		return a->hint < b->hint ? -1 : 1;
+	return tuple_compare(a->tuple, b->tuple, key_def);
+}
+
+/**
+ * Compare memtx_hinted_tree record with key.
+ */
+static int
+memtx_hinted_tree_data_cmp_with_key(struct memtx_hinted_tree_data *a,
+				    struct memtx_hinted_tree_key_data *key,
+				    struct key_def *key_def)
+{
+	if (a->hint != key->hint)
+		return a->hint < key->hint ? -1 : 1;
+	return tuple_compare_with_key(a->tuple, key->key, key->part_count,
+				      key_def);
+}
+
+/**
+ * Initialize memtx_hinted_tree or memtx_hint_only_tree record
+ * with tuple and recalculate internal hint field.
+ */
+static void
+memtx_hinted_tree_data_set(struct memtx_hinted_tree_data *data,
+			   struct tuple *tuple, struct key_def *key_def)
+{
+	data->tuple = tuple;
+	data->hint = tuple != NULL ? tuple_hint(tuple, key_def) : 0;
+}
+
+/**
+ * Initialize memtx_hinted_tree or memtx_hint_only_tree key with
+ * key raw and part count and recalculate internal hint field.
+ */
+static void
+memtx_hinted_tree_key_data_set(struct memtx_hinted_tree_key_data *key_data,
+			       const char *key, uint32_t part_count,
+			       struct key_def *key_def)
+{
+	key_data->key = key;
+	key_data->part_count = part_count;
+	key_data->hint = key != NULL && part_count > 0 ?
+			 key_hint(key, key_def) : 0;
+}
+
+#define MEMTX_TREE_NAME memtx_hinted_tree
+#define memtx_tree_elem struct memtx_hinted_tree_data
+#define memtx_tree_key struct memtx_hinted_tree_key_data
+#define MEMTX_TREE_ELEM_EQUAL(elem_a_ptr, elem_b_ptr)				\
+	((elem_a_ptr)->tuple == (elem_b_ptr)->tuple)
+#define MEMTX_TREE_ELEM_CMP(elem_a_ptr, elem_b_ptr, key_def)			\
+	memtx_hinted_tree_data_cmp(elem_a_ptr, elem_b_ptr, key_def)
+#define MEMTX_TREE_ELEM_WITH_KEY_CMP(elem_ptr, key_ptr, key_def)		\
+	memtx_hinted_tree_data_cmp_with_key(elem_ptr, key_ptr, key_def)
+#define MEMTX_TREE_ELEM_SET(elem_ptr, tuple, key_def)				\
+	memtx_hinted_tree_data_set(elem_ptr, tuple, key_def)
+#define MEMTX_TREE_KEY_SET(key_ptr, key_val, part_count_val, key_def)		\
+	memtx_hinted_tree_key_data_set(key_ptr, key_val, part_count_val,	\
+				       key_def)
+#define MEMTX_TREE_ELEM_GET(elem_ptr) ((elem_ptr)->tuple)
+#define MEMTX_TREE_KEY_GET(key_ptr, part_count_ptr)				\
+	({*part_count_ptr = (key_ptr)->part_count; (key_ptr)->key;})
+
+#include "memtx_tree_impl.h"
+
+#undef memtx_tree_key
+#undef memtx_tree_elem
+#undef MEMTX_TREE_KEY_GET
+#undef MEMTX_TREE_ELEM_GET
+#undef MEMTX_TREE_KEY_SET
+#undef MEMTX_TREE_ELEM_SET
+#undef MEMTX_TREE_ELEM_WITH_KEY_CMP
+#undef MEMTX_TREE_ELEM_CMP
+#undef MEMTX_TREE_ELEM_EQUAL
+#undef memtx_tree_key
+#undef memtx_tree_elem
+#undef MEMTX_TREE_NAME
+
+/* }}} */
+
 struct index *
 memtx_tree_index_new(struct memtx_engine *memtx, struct index_def *def)
 {
+	if (def->cmp_def->parts->type == FIELD_TYPE_STRING)
+		return memtx_hinted_tree_index_new(memtx, def);
 	return memtx_tuple_tree_index_new(memtx, def);
 }
diff --git a/src/box/tuple_compare.cc b/src/box/tuple_compare.cc
index ded802c7d..744901d70 100644
--- a/src/box/tuple_compare.cc
+++ b/src/box/tuple_compare.cc
@@ -1321,4 +1321,105 @@ tuple_compare_with_key_create(const struct key_def *def)
 	       compare_with_key_slowpath_funcs[cmp_func_idx];
 }
 
+static uint64_t
+key_hint_default(const char *key, struct key_def *key_def)
+{
+	(void)key;
+	(void)key_def;
+	return 0;
+}
+
+static uint64_t
+tuple_hint_default(const struct tuple *tuple, struct key_def *key_def)
+{
+	(void)tuple;
+	(void)key_def;
+	return 0;
+}
+
+static uint64_t
+key_hint_string(const char *key, struct key_def *key_def)
+{
+	assert(key != NULL);
+	(void)key_def;
+	assert(key_def->parts->type == FIELD_TYPE_STRING);
+	assert(mp_typeof(*key) == MP_STR);
+	uint32_t len;
+	const unsigned char *str =
+		(const unsigned char *)mp_decode_str(&key, &len);
+	uint64_t result = 0;
+	/*
+	 * Map the sequence of characters in the hint's bytes in
+	 * the reverse order: the first character will be mapped
+	 * in the highest byte of the number, etc.
+	 * One additional bit encodes the presence of the next
+	 * sign.
+	 * 0bCHARBYTEU CHARBYTEU CHARBYTEU ... CHARBYTE0
+	 * The sequence constructed in this way provides a
+	 * comparison transitivity of strings no longer than 7
+	 * bytes.
+	 */
+	uint32_t process_len = MIN(len, sizeof(char) - 1);
+	for (uint32_t i = 0; i < process_len; i++) {
+		result <<= CHAR_BIT + 1;
+		result |= UCHAR_MAX + 1;
+		result |= str[i];
+	}
+	/*
+	 * If the length of the string is less than the 64-bit
+	 * hint can accommodate, the insignificant positions are
+	 * filled with 0.
+	 */
+	result <<= (CHAR_BIT + 1) * (sizeof(char) - 1 - process_len);
+	return result;
+}
+
+static uint64_t
+tuple_hint_string(const struct tuple *tuple, struct key_def *key_def)
+{
+	const char *field = tuple_field_by_part(tuple, key_def->parts);
+	return field != NULL ? key_hint_string(field, key_def) : 0;
+}
+
+static uint64_t
+key_hint_string_coll(const char *key, struct key_def *key_def)
+{
+	assert(key != NULL);
+	assert(key_def->parts->type == FIELD_TYPE_STRING);
+	assert(mp_typeof(*key) == MP_STR);
+	assert(key_def->parts->coll != NULL);
+	uint32_t len;
+	const char *str = mp_decode_str(&key, &len);
+	return key_def->parts->coll->hint(str, len, key_def->parts->coll);
+}
+
+static uint64_t
+tuple_hint_string_coll(const struct tuple *tuple, struct key_def *key_def)
+{
+	const char *field = tuple_field_by_part(tuple, key_def->parts);
+	return field != NULL ? key_hint_string_coll(field, key_def) : 0;
+}
+
+void
+tuple_hint_set(struct key_def *def)
+{
+	def->key_hint = key_hint_default;
+	def->tuple_hint = tuple_hint_default;
+	if (key_part_is_nullable(def->parts))
+		return;
+	if (def->parts->type == FIELD_TYPE_STRING && def->parts->coll != NULL) {
+		def->key_hint = key_hint_string_coll;
+		def->tuple_hint = tuple_hint_string_coll;
+		return;
+	}
+	switch (def->parts->type) {
+	case FIELD_TYPE_STRING:
+		def->key_hint = key_hint_string;
+		def->tuple_hint = tuple_hint_string;
+		break;
+	default:
+		break;
+	};
+}
+
 /* }}} tuple_compare_with_key */
diff --git a/src/box/tuple_compare.h b/src/box/tuple_compare.h
index e3a63204f..405460086 100644
--- a/src/box/tuple_compare.h
+++ b/src/box/tuple_compare.h
@@ -67,6 +67,13 @@ tuple_compare_create(const struct key_def *key_def);
 tuple_compare_with_key_t
 tuple_compare_with_key_create(const struct key_def *key_def);
 
+/**
+ * Initialize tuple_hint() and key_hint() functions for the key_def.
+ * @param key_def key definition to set up.
+ */
+void
+tuple_hint_set(struct key_def *key_def);
+
 #if defined(__cplusplus)
 } /* extern "C" */
 #endif /* defined(__cplusplus) */
diff --git a/src/coll.c b/src/coll.c
index 6d9c44dbf..5bb46a94f 100644
--- a/src/coll.c
+++ b/src/coll.c
@@ -33,6 +33,7 @@
 #include "third_party/PMurHash.h"
 #include "diag.h"
 #include "assoc.h"
+#include "limits.h"
 #include <unicode/ucol.h>
 #include <trivia/config.h>
 
@@ -133,6 +134,48 @@ coll_bin_hash(const char *s, size_t s_len, uint32_t *ph, uint32_t *pcarry,
 	return s_len;
 }
 
+/** Get a compare hint of a string using ICU collation. */
+static uint64_t
+coll_icu_hint(const char *s, size_t s_len, struct coll *coll)
+{
+	UCharIterator itr;
+	uiter_setUTF8(&itr, s, s_len);
+	uint8_t buf[7];
+	uint32_t state[2] = {0, 0};
+	UErrorCode status = U_ZERO_ERROR;
+	int32_t got = ucol_nextSortKeyPart(coll->collator, &itr, state, buf,
+					   sizeof(buf), &status);
+	assert(got >= 0 && got <= 7);
+	uint64_t result = 0;
+	for (int32_t i = 0; i < got; i++) {
+		result <<= 9;
+		result |= 0x100;
+		result |= buf[i];
+	}
+	result <<= 9 * (7 - got);
+	return result;
+}
+
+/**
+ * Get a compare hint of a string using BINARY collation.
+ * Works similar to key_hint_string, read it's comment for more
+ * details.
+ */
+static uint64_t
+coll_bin_hint(const char *s, size_t s_len, struct coll *coll)
+{
+	(void)coll;
+	uint64_t result = 0;
+	uint32_t process_len = MIN(s_len, sizeof(char) - 1);
+	for (uint32_t i = 0; i < process_len; i++) {
+		result <<= CHAR_BIT;
+		result |= UCHAR_MAX + 1;
+		result |= s[i];
+	}
+	result <<= (CHAR_BIT + 1) * (sizeof(char) - 1 - process_len);
+	return result;
+}
+
 /**
  * Set up ICU collator and init cmp and hash members of collation.
  * @param coll Collation to set up.
@@ -242,6 +285,7 @@ coll_icu_init_cmp(struct coll *coll, const struct coll_def *def)
 	}
 	coll->cmp = coll_icu_cmp;
 	coll->hash = coll_icu_hash;
+	coll->hint = coll_icu_hint;
 	return 0;
 }
 
@@ -332,6 +376,7 @@ coll_new(const struct coll_def *def)
 		coll->collator = NULL;
 		coll->cmp = coll_bin_cmp;
 		coll->hash = coll_bin_hash;
+		coll->hint = coll_bin_hint;
 		break;
 	default:
 		unreachable();
diff --git a/src/coll.h b/src/coll.h
index 9c725712a..53133dae3 100644
--- a/src/coll.h
+++ b/src/coll.h
@@ -47,6 +47,8 @@ typedef int (*coll_cmp_f)(const char *s, size_t s_len, const char *t,
 typedef uint32_t (*coll_hash_f)(const char *s, size_t s_len, uint32_t *ph,
 				uint32_t *pcarry, struct coll *coll);
 
+typedef uint64_t (*coll_hint_f)(const char *s, size_t s_len, struct coll *coll);
+
 struct UCollator;
 
 /**
@@ -61,6 +63,8 @@ struct coll {
 	/** String comparator. */
 	coll_cmp_f cmp;
 	coll_hash_f hash;
+	/** The pointer to routine calculating tuple hint. */
+	coll_hint_f hint;
 	/** Reference counter. */
 	int refs;
 	/**
-- 
2.20.1

Re: [tarantool-patches] [PATCH v2 1/4] box: move memtx_tree implementation to source file

[Konstantin Osipov]

* Kirill Shcherbatov <kshcherbatov@tarantool.org> [19/02/13 13:03]:
> Refactored memtx_tree code so that memtx_tree.h contained only
> the signature of the tree object constructor memtx_tree_index_new,
> while all implementation details were in memtx_tree.c.
> This will further allow to template the implementation details.
> 
> Needed for #3961

This patch is OK to push.

I am not sure if any of the following patches will be in, but
hiding more details in the implementation is always a good thing.


-- 
Konstantin Osipov, Moscow, Russia, +7 903 626 22 32
http://tarantool.io - www.twitter.com/kostja_osipov

Re: [tarantool-patches] [PATCH v2 4/4] box: introduce tuple compare hint for string index

[Konstantin Osipov]

* Kirill Shcherbatov <kshcherbatov@tarantool.org> [19/02/13 13:03]:
> From: Alexandr Lyapunov <aleks@tarantool.org>
> diff --git a/src/box/key_def.c b/src/box/key_def.c
> index 9411ade39..ceca1ebee 100644
> --- a/src/box/key_def.c
> +++ b/src/box/key_def.c
> @@ -135,6 +135,7 @@ key_def_set_cmp(struct key_def *def)
>  	def->tuple_compare_with_key = tuple_compare_with_key_create(def);
>  	tuple_hash_func_set(def);
>  	tuple_extract_key_set(def);
> +	tuple_hint_set(def);

I think the name of the function is confusing. The name suggests
that it says a tuple hint, whereas it sets a function which
evaluates the hint. Please prepare a separate patch which renames
existing functions tuple_hash_func_set and tuple_extract_key_set
to
key_def_set_{tuple_extract_key_func|tuple_hash_func|tuple_hint_func}.

> +/** @copydoc tuple_hint() */
> +typedef uint64_t (*tuple_hint_t)(const struct tuple *tuple,
> +				 struct key_def *key_def);

The func typedef should end with _f not with _t.

> +
> +/** @copydoc key_hint() */
> +typedef uint64_t (*key_hint_t)(const char *key, struct key_def *key_def);

Same here.

> +static int
> +memtx_hinted_tree_data_cmp(struct memtx_hinted_tree_data *a,
> +			   struct memtx_hinted_tree_data *b,
> +			   struct key_def *key_def)
> +{
> +	if (a->hint != b->hint)
> +		return a->hint < b->hint ? -1 : 1;
> +	return tuple_compare(a->tuple, b->tuple, key_def);
> +}

Looks like we need null-aware hints as well, to preserve online null ->
not null alter semantics. 

-- 
Konstantin Osipov, Moscow, Russia, +7 903 626 22 32
http://tarantool.io - www.twitter.com/kostja_osipov

Re: [tarantool-patches] [PATCH v2 4/4] box: introduce tuple compare hint for string index

[Kirill Shcherbatov]

Hi! I've implemented Kostya's concepts for compatible hints for UINT/INT.
Also fixed nullability troubles. Now alter looks fine for me.
I've thought about number/integer convertions, but such alter would not pass,
I guess.

=========================================

Implement functions for retrieving tuple hints for a particular
key_def. Hint is an integer that can be used for tuple comparison
optimization: if a hint of one tuple is less than a hint of another
then the first tuple is definitely less than the second; only if
hints are equal tuple_compare must be called for getting comparison
result.

Hints are calculated using only the first part of key_def.

Hints are only useful when:
 * they are precalculated and stored along with the tuple;
calculation is not cheap (cheaper than tuple_compare btw) but
precalculated hints allow to compare tuples without even fetching
tuple data.
 * first part of key_def is 'string'(for now)
 * since hint is calculated using only the first part of key_def
(and only first several characters if it is a string) this part
must be different with high probability for every tuple pair.

Part of #3961
---
 src/box/key_def.c         |   1 +
 src/box/key_def.h         |  44 +++++++++
 src/box/memtx_tree_decl.c | 125 ++++++++++++++++++++++++++
 src/box/tuple_compare.cc  | 182 ++++++++++++++++++++++++++++++++++++++
 src/box/tuple_compare.h   |   7 ++
 src/coll.c                |  45 ++++++++++
 src/coll.h                |   4 +
 7 files changed, 408 insertions(+)

diff --git a/src/box/key_def.c b/src/box/key_def.c
index 9411ade39..ceca1ebee 100644
--- a/src/box/key_def.c
+++ b/src/box/key_def.c
@@ -135,6 +135,7 @@ key_def_set_cmp(struct key_def *def)
 	def->tuple_compare_with_key = tuple_compare_with_key_create(def);
 	tuple_hash_func_set(def);
 	tuple_extract_key_set(def);
+	tuple_hint_set(def);
 }
 
 static void
diff --git a/src/box/key_def.h b/src/box/key_def.h
index bf3e63b6d..a2a0bbecb 100644
--- a/src/box/key_def.h
+++ b/src/box/key_def.h
@@ -153,6 +153,13 @@ typedef uint32_t (*tuple_hash_t)(const struct tuple *tuple,
 typedef uint32_t (*key_hash_t)(const char *key,
 				struct key_def *key_def);
 
+/** @copydoc tuple_hint() */
+typedef uint64_t (*tuple_hint_t)(const struct tuple *tuple,
+				 struct key_def *key_def);
+
+/** @copydoc key_hint() */
+typedef uint64_t (*key_hint_t)(const char *key, struct key_def *key_def);
+
 /* Definition of a multipart key. */
 struct key_def {
 	/** @see tuple_compare() */
@@ -167,6 +174,10 @@ struct key_def {
 	tuple_hash_t tuple_hash;
 	/** @see key_hash() */
 	key_hash_t key_hash;
+	/** @see tuple_hint() */
+	tuple_hint_t tuple_hint;
+	/** @see key_hint() */
+	key_hint_t key_hint;
 	/**
 	 * Minimal part count which always is unique. For example,
 	 * if a secondary index is unique, then
@@ -551,6 +562,39 @@ tuple_compare_with_key(const struct tuple *tuple, const char *key,
 	return key_def->tuple_compare_with_key(tuple, key, part_count, key_def);
 }
 
+/**
+ * Get a comparison hint of a tuple.
+ * Hint is such a function h(tuple) in terms of particular key_def that
+ * has follows rules:
+ * if h(t1) < h(t2) then t1 < t2;
+ * if h(t1) > h(t2) then t1 > t2;
+ * if t1 == t2 then h(t1) == h(t2);
+ * These rules means that instead of direct tuple vs tuple (or tuple vs key)
+ * comparison one may compare theirs hints first; and only if theirs hints
+ * are equal compare the tuples themselves.
+ * @param tuple - tuple to get hint of.
+ * @param key_def - key_def that defines which comparison is used.
+ * @return the hint.
+ */
+static inline uint64_t
+tuple_hint(const struct tuple *tuple, struct key_def *key_def)
+{
+	return key_def->tuple_hint(tuple, key_def);
+}
+
+/**
+ * Get a comparison hint of a key.
+ * @See tuple_hint for hint term definition.
+ * @param key - key to get hint of.
+ * @param key_def - key_def that defines which comparison is used.
+ * @return the hint.
+ */
+static inline uint64_t
+key_hint(const char *key, struct key_def *key_def)
+{
+	return key_def->key_hint(key, key_def);
+}
+
 #if defined(__cplusplus)
 } /* extern "C" */
 #endif /* defined(__cplusplus) */
diff --git a/src/box/memtx_tree_decl.c b/src/box/memtx_tree_decl.c
index 084a0594f..55016148b 100644
--- a/src/box/memtx_tree_decl.c
+++ b/src/box/memtx_tree_decl.c
@@ -77,8 +77,133 @@ struct memtx_tuple_tree_key_data {
 
 /* }}} */
 
+/* {{{ Memtx hinted and hint_only tree class. *******************/
+
+/**
+ * Struct that is used as a key in BPS tree definition in
+ * memtx_hint_only_tree and memtx_hinted_tree.
+*/
+struct memtx_hinted_tree_key_data {
+	/** Sequence of msgpacked search fields. */
+	const char *key;
+	/** Number of msgpacked search fields. */
+	uint32_t part_count;
+	/**
+	 * Compare hint. Is calculated automatically on 'set'
+	 * operation with memtx_hinted_tree_key_data_set().
+	 */
+	uint64_t hint;
+};
+
+/**
+ * Struct that is used as a key in BPS tree definition in
+ * memtx_hint_only_tree and memtx_hinted_tree.
+ */
+struct memtx_hinted_tree_data {
+	/** Tuple this node is representing. */
+	struct tuple *tuple;
+	/**
+	 * Compare hint. Is calculated automatically on 'set'
+	 * operation with memtx_hinted_tree_data_set().
+	 */
+	uint64_t hint;
+};
+
+/**
+ * Compare memtx_hinted_tree records.
+ */
+static int
+memtx_hinted_tree_data_cmp(struct memtx_hinted_tree_data *a,
+			   struct memtx_hinted_tree_data *b,
+			   struct key_def *key_def)
+{
+	if (a->hint != b->hint)
+		return a->hint < b->hint ? -1 : 1;
+	return tuple_compare(a->tuple, b->tuple, key_def);
+}
+
+/**
+ * Compare memtx_hinted_tree record with key.
+ */
+static int
+memtx_hinted_tree_data_cmp_with_key(struct memtx_hinted_tree_data *a,
+				    struct memtx_hinted_tree_key_data *key,
+				    struct key_def *key_def)
+{
+	if (a->hint != key->hint)
+		return a->hint < key->hint ? -1 : 1;
+	return tuple_compare_with_key(a->tuple, key->key, key->part_count,
+				      key_def);
+}
+
+/**
+ * Initialize memtx_hinted_tree or memtx_hint_only_tree record
+ * with tuple and recalculate internal hint field.
+ */
+static void
+memtx_hinted_tree_data_set(struct memtx_hinted_tree_data *data,
+			   struct tuple *tuple, struct key_def *key_def)
+{
+	data->tuple = tuple;
+	data->hint = tuple_hint(tuple, key_def);
+}
+
+/**
+ * Initialize memtx_hinted_tree or memtx_hint_only_tree key with
+ * key raw and part count and recalculate internal hint field.
+ */
+static void
+memtx_hinted_tree_key_data_set(struct memtx_hinted_tree_key_data *key_data,
+			       const char *key, uint32_t part_count,
+			       struct key_def *key_def)
+{
+	key_data->key = key;
+	key_data->part_count = part_count;
+	key_data->hint = key != NULL && part_count > 0 ?
+			 key_hint(key, key_def) : 0;
+}
+
+#define MEMTX_TREE_NAME memtx_hinted_tree
+#define memtx_tree_elem struct memtx_hinted_tree_data
+#define memtx_tree_key struct memtx_hinted_tree_key_data
+#define MEMTX_TREE_ELEM_EQUAL(elem_a_ptr, elem_b_ptr)				\
+	((elem_a_ptr)->tuple == (elem_b_ptr)->tuple)
+#define MEMTX_TREE_ELEM_CMP(elem_a_ptr, elem_b_ptr, key_def)			\
+	memtx_hinted_tree_data_cmp(elem_a_ptr, elem_b_ptr, key_def)
+#define MEMTX_TREE_ELEM_WITH_KEY_CMP(elem_ptr, key_ptr, key_def)		\
+	memtx_hinted_tree_data_cmp_with_key(elem_ptr, key_ptr, key_def)
+#define MEMTX_TREE_ELEM_SET(elem_ptr, tuple, key_def)				\
+	memtx_hinted_tree_data_set(elem_ptr, tuple, key_def)
+#define MEMTX_TREE_KEY_SET(key_ptr, key_val, part_count_val, key_def)		\
+	memtx_hinted_tree_key_data_set(key_ptr, key_val, part_count_val,	\
+				       key_def)
+#define MEMTX_TREE_ELEM_GET(elem_ptr) ((elem_ptr)->tuple)
+#define MEMTX_TREE_KEY_GET(key_ptr, part_count_ptr)				\
+	({*part_count_ptr = (key_ptr)->part_count; (key_ptr)->key;})
+
+#include "memtx_tree_impl.h"
+
+#undef memtx_tree_key
+#undef memtx_tree_elem
+#undef MEMTX_TREE_KEY_GET
+#undef MEMTX_TREE_ELEM_GET
+#undef MEMTX_TREE_KEY_SET
+#undef MEMTX_TREE_ELEM_SET
+#undef MEMTX_TREE_ELEM_WITH_KEY_CMP
+#undef MEMTX_TREE_ELEM_CMP
+#undef MEMTX_TREE_ELEM_EQUAL
+#undef memtx_tree_key
+#undef memtx_tree_elem
+#undef MEMTX_TREE_NAME
+
+/* }}} */
+
 struct index *
 memtx_tree_index_new(struct memtx_engine *memtx, struct index_def *def)
 {
+	if (def->cmp_def->parts->type == FIELD_TYPE_STRING ||
+	    def->cmp_def->parts->type == FIELD_TYPE_UNSIGNED ||
+	    def->cmp_def->parts->type == FIELD_TYPE_INTEGER)
+		return memtx_hinted_tree_index_new(memtx, def);
 	return memtx_tuple_tree_index_new(memtx, def);
 }
diff --git a/src/box/tuple_compare.cc b/src/box/tuple_compare.cc
index ded802c7d..6ebf625a4 100644
--- a/src/box/tuple_compare.cc
+++ b/src/box/tuple_compare.cc
@@ -1321,4 +1321,186 @@ tuple_compare_with_key_create(const struct key_def *def)
 	       compare_with_key_slowpath_funcs[cmp_func_idx];
 }
 
+static uint64_t
+key_hint_default(const char *key, struct key_def *key_def)
+{
+	(void)key;
+	(void)key_def;
+	return 0;
+}
+
+static uint64_t
+tuple_hint_default(const struct tuple *tuple, struct key_def *key_def)
+{
+	(void)tuple;
+	(void)key_def;
+	return 0;
+}
+
+template<bool is_nullable>
+static uint64_t
+key_hint_uint(const char *key, struct key_def *key_def)
+{
+	assert(key_part_is_nullable(key_def->parts) == is_nullable);
+	if (is_nullable && mp_typeof(*key) == MP_NIL)
+		return 0;
+	assert(mp_typeof(*key) == MP_UINT);
+	uint64_t val = mp_decode_uint(&key);
+	if (val > INT64_MAX)
+		return INT64_MAX;
+	return val - (uint64_t)INT64_MIN;
+}
+
+template<bool is_nullable>
+static uint64_t
+tuple_hint_uint(const struct tuple *tuple, struct key_def *key_def)
+{
+	assert(key_part_is_nullable(key_def->parts) == is_nullable);
+	const char *field = tuple_field_by_part(tuple, key_def->parts);
+	if (is_nullable && field == NULL)
+		return 0;
+	return key_hint_uint<is_nullable>(field, key_def);
+}
+
+template<bool is_nullable>
+static uint64_t
+key_hint_int(const char *key, struct key_def *key_def)
+{
+	assert(key_part_is_nullable(key_def->parts) == is_nullable);
+	if (is_nullable && mp_typeof(*key) == MP_NIL)
+		return 0;
+	if (mp_typeof(*key) == MP_UINT) {
+		return key_hint_uint<is_nullable>(key, key_def);
+	} else {
+		assert(key_def->parts->type == FIELD_TYPE_INTEGER);
+		assert(mp_typeof(*key) == MP_INT);
+		int64_t val = mp_decode_int(&key);
+		return (uint64_t)val - (uint64_t)INT64_MIN;
+	}
+}
+
+template<bool is_nullable>
+static uint64_t
+tuple_hint_int(const struct tuple *tuple, struct key_def *key_def)
+{
+	assert(key_part_is_nullable(key_def->parts) == is_nullable);
+	const char *field = tuple_field_by_part(tuple, key_def->parts);
+	if (is_nullable && field == NULL)
+		return 0;
+	return key_hint_int<is_nullable>(field, key_def);
+}
+
+template<bool is_nullable>
+static uint64_t
+key_hint_string(const char *key, struct key_def *key_def)
+{
+	assert(key_part_is_nullable(key_def->parts) == is_nullable);
+	if (is_nullable && mp_typeof(*key) == MP_NIL)
+		return 0;
+	assert(key_def->parts->type == FIELD_TYPE_STRING);
+	assert(mp_typeof(*key) == MP_STR);
+	uint32_t len;
+	const unsigned char *str =
+		(const unsigned char *)mp_decode_str(&key, &len);
+	uint64_t result = 0;
+	/*
+	 * Map the sequence of characters in the hint's bytes in
+	 * the reverse order: the first character will be mapped
+	 * in the highest byte of the number, etc.
+	 * One additional bit encodes the presence of the next
+	 * sign.
+	 * 0bCHARBYTEU CHARBYTEU CHARBYTEU ... CHARBYTE0
+	 * The sequence constructed in this way provides a
+	 * comparison transitivity of strings no longer than 7
+	 * bytes.
+	 */
+	uint32_t process_len = MIN(len, 7);
+	for (uint32_t i = 0; i < process_len; i++) {
+		result <<= 9;
+		result |= 0x100;
+		result |= str[i];
+	}
+	/*
+	 * If the length of the string is less than the 64-bit
+	 * hint can accommodate, the insignificant positions are
+	 * filled with 0.
+	 */
+	result <<= 9 * (7 - process_len);
+	return result;
+}
+
+template<bool is_nullable>
+static uint64_t
+tuple_hint_string(const struct tuple *tuple, struct key_def *key_def)
+{
+	assert(key_part_is_nullable(key_def->parts) == is_nullable);
+	const char *field = tuple_field_by_part(tuple, key_def->parts);
+	if (is_nullable && field == NULL)
+		return 0;
+	return key_hint_string<is_nullable>(field, key_def);
+}
+
+template<bool is_nullable>
+static uint64_t
+key_hint_string_coll(const char *key, struct key_def *key_def)
+{
+	assert(key_part_is_nullable(key_def->parts) == is_nullable);
+	if (is_nullable && mp_typeof(*key) == MP_NIL)
+		return 0;
+	assert(key_def->parts->type == FIELD_TYPE_STRING);
+	assert(mp_typeof(*key) == MP_STR);
+	assert(key_def->parts->coll != NULL);
+	uint32_t len;
+	const char *str = mp_decode_str(&key, &len);
+	return key_def->parts->coll->hint(str, len, key_def->parts->coll);
+}
+
+template<bool is_nullable>
+static uint64_t
+tuple_hint_string_coll(const struct tuple *tuple, struct key_def *key_def)
+{
+	assert(key_part_is_nullable(key_def->parts) == is_nullable);
+	const char *field = tuple_field_by_part(tuple, key_def->parts);
+	if (is_nullable && field == NULL)
+		return 0;
+	return key_hint_string_coll<is_nullable>(field, key_def);
+}
+
+void
+tuple_hint_set(struct key_def *def)
+{
+	def->key_hint = key_hint_default;
+	def->tuple_hint = tuple_hint_default;
+	bool is_nullable = key_part_is_nullable(def->parts);
+	if (def->parts->type == FIELD_TYPE_STRING && def->parts->coll != NULL) {
+		def->key_hint = is_nullable ? key_hint_string_coll<true> :
+					      key_hint_string_coll<false>;
+		def->tuple_hint = is_nullable ? tuple_hint_string_coll<true> :
+						tuple_hint_string_coll<false>;
+		return;
+	}
+	switch (def->parts->type) {
+	case FIELD_TYPE_UNSIGNED:
+		def->key_hint = is_nullable ? key_hint_uint<true> :
+					      key_hint_uint<false>;
+		def->tuple_hint = is_nullable ? tuple_hint_uint<true> :
+						tuple_hint_uint<false>;
+		break;
+	case FIELD_TYPE_INTEGER:
+		def->key_hint = is_nullable ? key_hint_int<true> :
+					      key_hint_int<false>;
+		def->tuple_hint = is_nullable ? tuple_hint_int<true> :
+						tuple_hint_int<false>;
+		break;
+	case FIELD_TYPE_STRING:
+		def->key_hint = is_nullable ? key_hint_string<true> :
+					      key_hint_string<false>;
+		def->tuple_hint = is_nullable ? tuple_hint_string<true> :
+						tuple_hint_string<false>;
+		break;
+	default:
+		break;
+	};
+}
+
 /* }}} tuple_compare_with_key */
diff --git a/src/box/tuple_compare.h b/src/box/tuple_compare.h
index e3a63204f..405460086 100644
--- a/src/box/tuple_compare.h
+++ b/src/box/tuple_compare.h
@@ -67,6 +67,13 @@ tuple_compare_create(const struct key_def *key_def);
 tuple_compare_with_key_t
 tuple_compare_with_key_create(const struct key_def *key_def);
 
+/**
+ * Initialize tuple_hint() and key_hint() functions for the key_def.
+ * @param key_def key definition to set up.
+ */
+void
+tuple_hint_set(struct key_def *key_def);
+
 #if defined(__cplusplus)
 } /* extern "C" */
 #endif /* defined(__cplusplus) */
diff --git a/src/coll.c b/src/coll.c
index 6d9c44dbf..0e7c8ec92 100644
--- a/src/coll.c
+++ b/src/coll.c
@@ -33,6 +33,7 @@
 #include "third_party/PMurHash.h"
 #include "diag.h"
 #include "assoc.h"
+#include "limits.h"
 #include <unicode/ucol.h>
 #include <trivia/config.h>
 
@@ -133,6 +134,48 @@ coll_bin_hash(const char *s, size_t s_len, uint32_t *ph, uint32_t *pcarry,
 	return s_len;
 }
 
+/** Get a compare hint of a string using ICU collation. */
+static uint64_t
+coll_icu_hint(const char *s, size_t s_len, struct coll *coll)
+{
+	UCharIterator itr;
+	uiter_setUTF8(&itr, s, s_len);
+	uint8_t buf[7];
+	uint32_t state[2] = {0, 0};
+	UErrorCode status = U_ZERO_ERROR;
+	int32_t got = ucol_nextSortKeyPart(coll->collator, &itr, state, buf,
+					   sizeof(buf), &status);
+	assert(got >= 0 && got <= 7);
+	uint64_t result = 0;
+	for (int32_t i = 0; i < got; i++) {
+		result <<= 9;
+		result |= 0x100;
+		result |= buf[i];
+	}
+	result <<= 9 * (7 - got);
+	return result;
+}
+
+/**
+ * Get a compare hint of a string using BINARY collation.
+ * Works similar to key_hint_string, read it's comment for more
+ * details.
+ */
+static uint64_t
+coll_bin_hint(const char *s, size_t s_len, struct coll *coll)
+{
+	(void)coll;
+	uint64_t result = 0;
+	uint32_t process_len = MIN(s_len, 7);
+	for (uint32_t i = 0; i < process_len; i++) {
+		result <<= 9;
+		result |= 0x100;
+		result |= s[i];
+	}
+	result <<= 9 * (7 - process_len);
+	return result;
+}
+
 /**
  * Set up ICU collator and init cmp and hash members of collation.
  * @param coll Collation to set up.
@@ -242,6 +285,7 @@ coll_icu_init_cmp(struct coll *coll, const struct coll_def *def)
 	}
 	coll->cmp = coll_icu_cmp;
 	coll->hash = coll_icu_hash;
+	coll->hint = coll_icu_hint;
 	return 0;
 }
 
@@ -332,6 +376,7 @@ coll_new(const struct coll_def *def)
 		coll->collator = NULL;
 		coll->cmp = coll_bin_cmp;
 		coll->hash = coll_bin_hash;
+		coll->hint = coll_bin_hint;
 		break;
 	default:
 		unreachable();
diff --git a/src/coll.h b/src/coll.h
index 9c725712a..53133dae3 100644
--- a/src/coll.h
+++ b/src/coll.h
@@ -47,6 +47,8 @@ typedef int (*coll_cmp_f)(const char *s, size_t s_len, const char *t,
 typedef uint32_t (*coll_hash_f)(const char *s, size_t s_len, uint32_t *ph,
 				uint32_t *pcarry, struct coll *coll);
 
+typedef uint64_t (*coll_hint_f)(const char *s, size_t s_len, struct coll *coll);
+
 struct UCollator;
 
 /**
@@ -61,6 +63,8 @@ struct coll {
 	/** String comparator. */
 	coll_cmp_f cmp;
 	coll_hash_f hash;
+	/** The pointer to routine calculating tuple hint. */
+	coll_hint_f hint;
 	/** Reference counter. */
 	int refs;
 	/**
-- 
2.20.1

Re: [tarantool-patches] Re: [PATCH v2 4/4] box: introduce tuple compare hint for string index

[Konstantin Osipov]

* Kirill Shcherbatov <kshcherbatov@tarantool.org> [19/02/15 21:36]:
> Hi! I've implemented Kostya's concepts for compatible hints for UINT/INT.
> Also fixed nullability troubles. Now alter looks fine for me.
> I've thought about number/integer convertions, but such alter would not pass,
> I guess.
> 

Do you have tests for this or have you checked that specific tests
exist? E.g. when tuple hint is used *and* we change nullability
back and forth.

BTW, have you checked changes in collation, do they work?


-- 
Konstantin Osipov, Moscow, Russia, +7 903 626 22 32
http://tarantool.io - www.twitter.com/kostja_osipov

Re: [tarantool-patches] Re: [PATCH v2 4/4] box: introduce tuple compare hint for string index

[Kirill Shcherbatov]

Hm, it looks like introduced before collation hint for binary collation is a not working.
(I've dropped icu_bin_hint for now)
This is a particular case in which there is no collator object, so we can do without
hints at all in this case.

====================================================

Implement functions for retrieving tuple hints for a particular
key_def. Hint is an integer that can be used for tuple comparison
optimization: if a hint of one tuple is less than a hint of another
then the first tuple is definitely less than the second; only if
hints are equal tuple_compare must be called for getting comparison
result.

Hints are calculated using only the first part of key_def.

Hints are only useful when:
 * they are precalculated and stored along with the tuple;
calculation is not cheap (cheaper than tuple_compare btw) but
precalculated hints allow to compare tuples without even fetching
tuple data.
 * first part of key_def is 'string'(for now)
 * since hint is calculated using only the first part of key_def
(and only first several characters if it is a string) this part
must be different with high probability for every tuple pair.

Closes #3961
---
 src/box/key_def.c         |   1 +
 src/box/key_def.h         |  44 +++++++++
 src/box/memtx_tree_decl.c | 125 ++++++++++++++++++++++++++
 src/box/tuple_compare.cc  | 185 ++++++++++++++++++++++++++++++++++++++
 src/box/tuple_compare.h   |   7 ++
 src/coll.c                |  24 +++++
 src/coll.h                |   4 +
 7 files changed, 390 insertions(+)

diff --git a/src/box/key_def.c b/src/box/key_def.c
index 9411ade39..ceca1ebee 100644
--- a/src/box/key_def.c
+++ b/src/box/key_def.c
@@ -135,6 +135,7 @@ key_def_set_cmp(struct key_def *def)
 	def->tuple_compare_with_key = tuple_compare_with_key_create(def);
 	tuple_hash_func_set(def);
 	tuple_extract_key_set(def);
+	tuple_hint_set(def);
 }
 
 static void
diff --git a/src/box/key_def.h b/src/box/key_def.h
index bf3e63b6d..a2a0bbecb 100644
--- a/src/box/key_def.h
+++ b/src/box/key_def.h
@@ -153,6 +153,13 @@ typedef uint32_t (*tuple_hash_t)(const struct tuple *tuple,
 typedef uint32_t (*key_hash_t)(const char *key,
 				struct key_def *key_def);
 
+/** @copydoc tuple_hint() */
+typedef uint64_t (*tuple_hint_t)(const struct tuple *tuple,
+				 struct key_def *key_def);
+
+/** @copydoc key_hint() */
+typedef uint64_t (*key_hint_t)(const char *key, struct key_def *key_def);
+
 /* Definition of a multipart key. */
 struct key_def {
 	/** @see tuple_compare() */
@@ -167,6 +174,10 @@ struct key_def {
 	tuple_hash_t tuple_hash;
 	/** @see key_hash() */
 	key_hash_t key_hash;
+	/** @see tuple_hint() */
+	tuple_hint_t tuple_hint;
+	/** @see key_hint() */
+	key_hint_t key_hint;
 	/**
 	 * Minimal part count which always is unique. For example,
 	 * if a secondary index is unique, then
@@ -551,6 +562,39 @@ tuple_compare_with_key(const struct tuple *tuple, const char *key,
 	return key_def->tuple_compare_with_key(tuple, key, part_count, key_def);
 }
 
+/**
+ * Get a comparison hint of a tuple.
+ * Hint is such a function h(tuple) in terms of particular key_def that
+ * has follows rules:
+ * if h(t1) < h(t2) then t1 < t2;
+ * if h(t1) > h(t2) then t1 > t2;
+ * if t1 == t2 then h(t1) == h(t2);
+ * These rules means that instead of direct tuple vs tuple (or tuple vs key)
+ * comparison one may compare theirs hints first; and only if theirs hints
+ * are equal compare the tuples themselves.
+ * @param tuple - tuple to get hint of.
+ * @param key_def - key_def that defines which comparison is used.
+ * @return the hint.
+ */
+static inline uint64_t
+tuple_hint(const struct tuple *tuple, struct key_def *key_def)
+{
+	return key_def->tuple_hint(tuple, key_def);
+}
+
+/**
+ * Get a comparison hint of a key.
+ * @See tuple_hint for hint term definition.
+ * @param key - key to get hint of.
+ * @param key_def - key_def that defines which comparison is used.
+ * @return the hint.
+ */
+static inline uint64_t
+key_hint(const char *key, struct key_def *key_def)
+{
+	return key_def->key_hint(key, key_def);
+}
+
 #if defined(__cplusplus)
 } /* extern "C" */
 #endif /* defined(__cplusplus) */
diff --git a/src/box/memtx_tree_decl.c b/src/box/memtx_tree_decl.c
index 084a0594f..55016148b 100644
--- a/src/box/memtx_tree_decl.c
+++ b/src/box/memtx_tree_decl.c
@@ -77,8 +77,133 @@ struct memtx_tuple_tree_key_data {
 
 /* }}} */
 
+/* {{{ Memtx hinted and hint_only tree class. *******************/
+
+/**
+ * Struct that is used as a key in BPS tree definition in
+ * memtx_hint_only_tree and memtx_hinted_tree.
+*/
+struct memtx_hinted_tree_key_data {
+	/** Sequence of msgpacked search fields. */
+	const char *key;
+	/** Number of msgpacked search fields. */
+	uint32_t part_count;
+	/**
+	 * Compare hint. Is calculated automatically on 'set'
+	 * operation with memtx_hinted_tree_key_data_set().
+	 */
+	uint64_t hint;
+};
+
+/**
+ * Struct that is used as a key in BPS tree definition in
+ * memtx_hint_only_tree and memtx_hinted_tree.
+ */
+struct memtx_hinted_tree_data {
+	/** Tuple this node is representing. */
+	struct tuple *tuple;
+	/**
+	 * Compare hint. Is calculated automatically on 'set'
+	 * operation with memtx_hinted_tree_data_set().
+	 */
+	uint64_t hint;
+};
+
+/**
+ * Compare memtx_hinted_tree records.
+ */
+static int
+memtx_hinted_tree_data_cmp(struct memtx_hinted_tree_data *a,
+			   struct memtx_hinted_tree_data *b,
+			   struct key_def *key_def)
+{
+	if (a->hint != b->hint)
+		return a->hint < b->hint ? -1 : 1;
+	return tuple_compare(a->tuple, b->tuple, key_def);
+}
+
+/**
+ * Compare memtx_hinted_tree record with key.
+ */
+static int
+memtx_hinted_tree_data_cmp_with_key(struct memtx_hinted_tree_data *a,
+				    struct memtx_hinted_tree_key_data *key,
+				    struct key_def *key_def)
+{
+	if (a->hint != key->hint)
+		return a->hint < key->hint ? -1 : 1;
+	return tuple_compare_with_key(a->tuple, key->key, key->part_count,
+				      key_def);
+}
+
+/**
+ * Initialize memtx_hinted_tree or memtx_hint_only_tree record
+ * with tuple and recalculate internal hint field.
+ */
+static void
+memtx_hinted_tree_data_set(struct memtx_hinted_tree_data *data,
+			   struct tuple *tuple, struct key_def *key_def)
+{
+	data->tuple = tuple;
+	data->hint = tuple_hint(tuple, key_def);
+}
+
+/**
+ * Initialize memtx_hinted_tree or memtx_hint_only_tree key with
+ * key raw and part count and recalculate internal hint field.
+ */
+static void
+memtx_hinted_tree_key_data_set(struct memtx_hinted_tree_key_data *key_data,
+			       const char *key, uint32_t part_count,
+			       struct key_def *key_def)
+{
+	key_data->key = key;
+	key_data->part_count = part_count;
+	key_data->hint = key != NULL && part_count > 0 ?
+			 key_hint(key, key_def) : 0;
+}
+
+#define MEMTX_TREE_NAME memtx_hinted_tree
+#define memtx_tree_elem struct memtx_hinted_tree_data
+#define memtx_tree_key struct memtx_hinted_tree_key_data
+#define MEMTX_TREE_ELEM_EQUAL(elem_a_ptr, elem_b_ptr)				\
+	((elem_a_ptr)->tuple == (elem_b_ptr)->tuple)
+#define MEMTX_TREE_ELEM_CMP(elem_a_ptr, elem_b_ptr, key_def)			\
+	memtx_hinted_tree_data_cmp(elem_a_ptr, elem_b_ptr, key_def)
+#define MEMTX_TREE_ELEM_WITH_KEY_CMP(elem_ptr, key_ptr, key_def)		\
+	memtx_hinted_tree_data_cmp_with_key(elem_ptr, key_ptr, key_def)
+#define MEMTX_TREE_ELEM_SET(elem_ptr, tuple, key_def)				\
+	memtx_hinted_tree_data_set(elem_ptr, tuple, key_def)
+#define MEMTX_TREE_KEY_SET(key_ptr, key_val, part_count_val, key_def)		\
+	memtx_hinted_tree_key_data_set(key_ptr, key_val, part_count_val,	\
+				       key_def)
+#define MEMTX_TREE_ELEM_GET(elem_ptr) ((elem_ptr)->tuple)
+#define MEMTX_TREE_KEY_GET(key_ptr, part_count_ptr)				\
+	({*part_count_ptr = (key_ptr)->part_count; (key_ptr)->key;})
+
+#include "memtx_tree_impl.h"
+
+#undef memtx_tree_key
+#undef memtx_tree_elem
+#undef MEMTX_TREE_KEY_GET
+#undef MEMTX_TREE_ELEM_GET
+#undef MEMTX_TREE_KEY_SET
+#undef MEMTX_TREE_ELEM_SET
+#undef MEMTX_TREE_ELEM_WITH_KEY_CMP
+#undef MEMTX_TREE_ELEM_CMP
+#undef MEMTX_TREE_ELEM_EQUAL
+#undef memtx_tree_key
+#undef memtx_tree_elem
+#undef MEMTX_TREE_NAME
+
+/* }}} */
+
 struct index *
 memtx_tree_index_new(struct memtx_engine *memtx, struct index_def *def)
 {
+	if (def->cmp_def->parts->type == FIELD_TYPE_STRING ||
+	    def->cmp_def->parts->type == FIELD_TYPE_UNSIGNED ||
+	    def->cmp_def->parts->type == FIELD_TYPE_INTEGER)
+		return memtx_hinted_tree_index_new(memtx, def);
 	return memtx_tuple_tree_index_new(memtx, def);
 }
diff --git a/src/box/tuple_compare.cc b/src/box/tuple_compare.cc
index ded802c7d..5845235ff 100644
--- a/src/box/tuple_compare.cc
+++ b/src/box/tuple_compare.cc
@@ -1321,4 +1321,189 @@ tuple_compare_with_key_create(const struct key_def *def)
 	       compare_with_key_slowpath_funcs[cmp_func_idx];
 }
 
+static uint64_t
+key_hint_default(const char *key, struct key_def *key_def)
+{
+	(void)key;
+	(void)key_def;
+	return 0;
+}
+
+static uint64_t
+tuple_hint_default(const struct tuple *tuple, struct key_def *key_def)
+{
+	(void)tuple;
+	(void)key_def;
+	return 0;
+}
+
+template<bool is_nullable>
+static uint64_t
+key_hint_uint(const char *key, struct key_def *key_def)
+{
+	(void)key_def;
+	assert(key_part_is_nullable(key_def->parts) == is_nullable);
+	if (is_nullable && mp_typeof(*key) == MP_NIL)
+		return 0;
+	assert(mp_typeof(*key) == MP_UINT);
+	uint64_t val = mp_decode_uint(&key);
+	if (val > INT64_MAX)
+		return INT64_MAX;
+	return val - (uint64_t)INT64_MIN;
+}
+
+template<bool is_nullable>
+static uint64_t
+tuple_hint_uint(const struct tuple *tuple, struct key_def *key_def)
+{
+	assert(key_part_is_nullable(key_def->parts) == is_nullable);
+	const char *field = tuple_field_by_part(tuple, key_def->parts);
+	if (is_nullable && field == NULL)
+		return 0;
+	return key_hint_uint<is_nullable>(field, key_def);
+}
+
+template<bool is_nullable>
+static uint64_t
+key_hint_int(const char *key, struct key_def *key_def)
+{
+	assert(key_part_is_nullable(key_def->parts) == is_nullable);
+	if (is_nullable && mp_typeof(*key) == MP_NIL)
+		return 0;
+	if (mp_typeof(*key) == MP_UINT) {
+		return key_hint_uint<is_nullable>(key, key_def);
+	} else {
+		assert(key_def->parts->type == FIELD_TYPE_INTEGER);
+		assert(mp_typeof(*key) == MP_INT);
+		int64_t val = mp_decode_int(&key);
+		return (uint64_t)val - (uint64_t)INT64_MIN;
+	}
+}
+
+template<bool is_nullable>
+static uint64_t
+tuple_hint_int(const struct tuple *tuple, struct key_def *key_def)
+{
+	assert(key_part_is_nullable(key_def->parts) == is_nullable);
+	const char *field = tuple_field_by_part(tuple, key_def->parts);
+	if (is_nullable && field == NULL)
+		return 0;
+	return key_hint_int<is_nullable>(field, key_def);
+}
+
+template<bool is_nullable>
+static uint64_t
+key_hint_string(const char *key, struct key_def *key_def)
+{
+	(void)key_def;
+	assert(key_part_is_nullable(key_def->parts) == is_nullable);
+	if (is_nullable && mp_typeof(*key) == MP_NIL)
+		return 0;
+	assert(key_def->parts->type == FIELD_TYPE_STRING);
+	assert(mp_typeof(*key) == MP_STR);
+	uint32_t len;
+	const unsigned char *str =
+		(const unsigned char *)mp_decode_str(&key, &len);
+	uint64_t result = 0;
+	/*
+	 * Map the sequence of characters in the hint's bytes in
+	 * the reverse order: the first character will be mapped
+	 * in the highest byte of the number, etc.
+	 * One additional bit encodes the presence of the next
+	 * sign.
+	 * 0bCHARBYTEU CHARBYTEU CHARBYTEU ... CHARBYTE0
+	 * The sequence constructed in this way provides a
+	 * comparison transitivity of strings no longer than 7
+	 * bytes.
+	 */
+	uint32_t process_len = MIN(len, 7);
+	for (uint32_t i = 0; i < process_len; i++) {
+		result <<= 9;
+		result |= 0x100;
+		result |= str[i];
+	}
+	/*
+	 * If the length of the string is less than the 64-bit
+	 * hint can accommodate, the insignificant positions are
+	 * filled with 0.
+	 */
+	result <<= 9 * (7 - process_len);
+	return result;
+}
+
+template<bool is_nullable>
+static uint64_t
+tuple_hint_string(const struct tuple *tuple, struct key_def *key_def)
+{
+	assert(key_part_is_nullable(key_def->parts) == is_nullable);
+	const char *field = tuple_field_by_part(tuple, key_def->parts);
+	if (is_nullable && field == NULL)
+		return 0;
+	return key_hint_string<is_nullable>(field, key_def);
+}
+
+template<bool is_nullable>
+static uint64_t
+key_hint_string_coll(const char *key, struct key_def *key_def)
+{
+	assert(key_part_is_nullable(key_def->parts) == is_nullable);
+	if (is_nullable && mp_typeof(*key) == MP_NIL)
+		return 0;
+	assert(key_def->parts->type == FIELD_TYPE_STRING);
+	assert(mp_typeof(*key) == MP_STR);
+	assert(key_def->parts->coll != NULL);
+	uint32_t len;
+	const char *str = mp_decode_str(&key, &len);
+	return key_def->parts->coll->hint(str, len, key_def->parts->coll);
+}
+
+template<bool is_nullable>
+static uint64_t
+tuple_hint_string_coll(const struct tuple *tuple, struct key_def *key_def)
+{
+	assert(key_part_is_nullable(key_def->parts) == is_nullable);
+	const char *field = tuple_field_by_part(tuple, key_def->parts);
+	if (is_nullable && field == NULL)
+		return 0;
+	return key_hint_string_coll<is_nullable>(field, key_def);
+}
+
+void
+tuple_hint_set(struct key_def *def)
+{
+	def->key_hint = key_hint_default;
+	def->tuple_hint = tuple_hint_default;
+	bool is_nullable = key_part_is_nullable(def->parts);
+	if (def->parts->type == FIELD_TYPE_STRING && def->parts->coll != NULL &&
+	    def->parts->coll->type != COLL_TYPE_BINARY) {
+		def->key_hint = is_nullable ? key_hint_string_coll<true> :
+					      key_hint_string_coll<false>;
+		def->tuple_hint = is_nullable ? tuple_hint_string_coll<true> :
+						tuple_hint_string_coll<false>;
+		return;
+	}
+	switch (def->parts->type) {
+	case FIELD_TYPE_UNSIGNED:
+		def->key_hint = is_nullable ? key_hint_uint<true> :
+					      key_hint_uint<false>;
+		def->tuple_hint = is_nullable ? tuple_hint_uint<true> :
+						tuple_hint_uint<false>;
+		break;
+	case FIELD_TYPE_INTEGER:
+		def->key_hint = is_nullable ? key_hint_int<true> :
+					      key_hint_int<false>;
+		def->tuple_hint = is_nullable ? tuple_hint_int<true> :
+						tuple_hint_int<false>;
+		break;
+	case FIELD_TYPE_STRING:
+		def->key_hint = is_nullable ? key_hint_string<true> :
+					      key_hint_string<false>;
+		def->tuple_hint = is_nullable ? tuple_hint_string<true> :
+						tuple_hint_string<false>;
+		break;
+	default:
+		break;
+	};
+}
+
 /* }}} tuple_compare_with_key */
diff --git a/src/box/tuple_compare.h b/src/box/tuple_compare.h
index e3a63204f..405460086 100644
--- a/src/box/tuple_compare.h
+++ b/src/box/tuple_compare.h
@@ -67,6 +67,13 @@ tuple_compare_create(const struct key_def *key_def);
 tuple_compare_with_key_t
 tuple_compare_with_key_create(const struct key_def *key_def);
 
+/**
+ * Initialize tuple_hint() and key_hint() functions for the key_def.
+ * @param key_def key definition to set up.
+ */
+void
+tuple_hint_set(struct key_def *key_def);
+
 #if defined(__cplusplus)
 } /* extern "C" */
 #endif /* defined(__cplusplus) */
diff --git a/src/coll.c b/src/coll.c
index 6d9c44dbf..922f03944 100644
--- a/src/coll.c
+++ b/src/coll.c
@@ -133,6 +133,28 @@ coll_bin_hash(const char *s, size_t s_len, uint32_t *ph, uint32_t *pcarry,
 	return s_len;
 }
 
+/** Get a compare hint of a string using ICU collation. */
+static uint64_t
+coll_icu_hint(const char *s, size_t s_len, struct coll *coll)
+{
+	UCharIterator itr;
+	uiter_setUTF8(&itr, s, s_len);
+	uint8_t buf[7];
+	uint32_t state[2] = {0, 0};
+	UErrorCode status = U_ZERO_ERROR;
+	int32_t got = ucol_nextSortKeyPart(coll->collator, &itr, state, buf,
+					   sizeof(buf), &status);
+	assert(got >= 0 && got <= 7);
+	uint64_t result = 0;
+	for (int32_t i = 0; i < got; i++) {
+		result <<= 9;
+		result |= 0x100;
+		result |= buf[i];
+	}
+	result <<= 9 * (7 - got);
+	return result;
+}
+
 /**
  * Set up ICU collator and init cmp and hash members of collation.
  * @param coll Collation to set up.
@@ -242,6 +264,7 @@ coll_icu_init_cmp(struct coll *coll, const struct coll_def *def)
 	}
 	coll->cmp = coll_icu_cmp;
 	coll->hash = coll_icu_hash;
+	coll->hint = coll_icu_hint;
 	return 0;
 }
 
@@ -332,6 +355,7 @@ coll_new(const struct coll_def *def)
 		coll->collator = NULL;
 		coll->cmp = coll_bin_cmp;
 		coll->hash = coll_bin_hash;
+		coll->hint = NULL;
 		break;
 	default:
 		unreachable();
diff --git a/src/coll.h b/src/coll.h
index 9c725712a..53133dae3 100644
--- a/src/coll.h
+++ b/src/coll.h
@@ -47,6 +47,8 @@ typedef int (*coll_cmp_f)(const char *s, size_t s_len, const char *t,
 typedef uint32_t (*coll_hash_f)(const char *s, size_t s_len, uint32_t *ph,
 				uint32_t *pcarry, struct coll *coll);
 
+typedef uint64_t (*coll_hint_f)(const char *s, size_t s_len, struct coll *coll);
+
 struct UCollator;
 
 /**
@@ -61,6 +63,8 @@ struct coll {
 	/** String comparator. */
 	coll_cmp_f cmp;
 	coll_hash_f hash;
+	/** The pointer to routine calculating tuple hint. */
+	coll_hint_f hint;
 	/** Reference counter. */
 	int refs;
 	/**
-- 
2.20.1

Re: [PATCH v2 1/4] box: move memtx_tree implementation to source file

[Vladimir Davydov]

The subject line prefix should be 'memtx:' I think.

On Wed, Feb 13, 2019 at 12:32:25PM +0300, Kirill Shcherbatov wrote:
> Refactored memtx_tree code so that memtx_tree.h contained only
> the signature of the tree object constructor memtx_tree_index_new,
> while all implementation details were in memtx_tree.c.
> This will further allow to template the implementation details.
> 
> Needed for #3961
> ---
>  src/box/memtx_tree.c | 62 ++++++++++++++++++++++++++++++++++++++--
>  src/box/memtx_tree.h | 68 ++------------------------------------------
>  2 files changed, 63 insertions(+), 67 deletions(-)

The patch is good, but I think we shouldn't stop at memtx_tree and do
the same for other memtx indexes - hash, bitset, rtree. Please do it in
the scope of this patch.

Re: [PATCH v2 2/4] box: rework memtx_tree to store arbitrary nodes

[Vladimir Davydov]

On Wed, Feb 13, 2019 at 12:32:26PM +0300, Kirill Shcherbatov wrote:
> Reworked memtx_tree class to use arbitrary containers as a tree
> nodes. This makes possible to implement tuple hints in subsequent
> patches.
> 
> The memtx_tree.c is currently used in a header manner. This is to
> ensure that functional changes in the patch do not mix with
> refactoring, that will be finished in the next commit.
> 
> Needed for #3961
> ---
>  src/box/CMakeLists.txt    |   2 +-
>  src/box/memtx_tree.c      | 498 ++++++++++++++++++++++++++------------
>  src/box/memtx_tree_decl.c |  84 +++++++
>  3 files changed, 434 insertions(+), 150 deletions(-)
>  create mode 100644 src/box/memtx_tree_decl.c
> 
> diff --git a/src/box/CMakeLists.txt b/src/box/CMakeLists.txt
> index 5521e489e..dc8cc2cd5 100644
> --- a/src/box/CMakeLists.txt
> +++ b/src/box/CMakeLists.txt
> @@ -64,7 +64,7 @@ add_library(box STATIC
>      index_def.c
>      iterator_type.c
>      memtx_hash.c
> -    memtx_tree.c
> +    memtx_tree_decl.c
>      memtx_rtree.c
>      memtx_bitset.c
>      engine.c
> diff --git a/src/box/memtx_tree.c b/src/box/memtx_tree.c
> index 2e8adb682..0874b7dc8 100644
> --- a/src/box/memtx_tree.c
> +++ b/src/box/memtx_tree.c
> @@ -1,5 +1,5 @@
>  /*
> - * Copyright 2010-2016, Tarantool AUTHORS, please see AUTHORS file.
> + * Copyright 2010-2019, Tarantool AUTHORS, please see AUTHORS file.
>   *
>   * Redistribution and use in source and binary forms, with or
>   * without modification, are permitted provided that the following
> @@ -28,72 +28,156 @@
>   * THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
>   * SUCH DAMAGE.
>   */
> -#include "memtx_tree.h"
> -#include "memtx_engine.h"
> -#include "space.h"
> -#include "schema.h" /* space_cache_find() */
> -#include "errinj.h"
> -#include "memory.h"
> -#include "fiber.h"
> -#include "tuple.h"
> -#include <third_party/qsort_arg.h>

Why touch header inclusions?

> +
> +#if defined(__cplusplus)
> +extern "C" {
> +#endif /* defined(__cplusplus) */
> +

This isn't needed in a header like this.

>  #include <small/mempool.h>
> +#include <third_party/qsort_arg.h>
> +#include "memtx_engine.h"
> +#include "schema.h"
>  
> -/**
> - * Struct that is used as a key in BPS tree definition.
> - */
> -struct memtx_tree_key_data {
> -	/** Sequence of msgpacked search fields. */
> -	const char *key;
> -	/** Number of msgpacked search fields. */
> -	uint32_t part_count;
> -};
> +#ifndef MEMTX_TREE_NAME
> +#error "MEMTX_TREE_NAME must be defined"
> +#endif
> +
> +#ifndef memtx_tree_elem
> +#error "memtx_tree_elem must be defined"
> +#endif
> +
> +#ifndef memtx_tree_key
> +#error "memtx_tree_key must be defined"
> +#endif

Let's please use _t suffix for types (memtx_tree_elem_t,
memtx_tree_key_t).

> +
> +#ifndef MEMTX_TREE_ELEM_CMP
> +#error "MEMTX_TREE_ELEM_CMP must be defined"
> +#endif
> +
> +#ifndef MEMTX_TREE_ELEM_WITH_KEY_CMP
> +#error "MEMTX_TREE_ELEM_WITH_KEY_CMP must be defined"
> +#endif

May be, call these MEMTX_TREE_COMPARE and MEMTX_TREE_COMPARE_KEY to
match BPS tree macros?

> +
> +#ifndef MEMTX_TREE_ELEM_SET
> +#error "MEMTX_TREE_ELEM_SET must be defined"
> +#endif
> +
> +#ifndef MEMTX_TREE_KEY_SET
> +#error "MEMTX_TREE_KEY_SET must be defined"
> +#endif
> +
> +#ifndef MEMTX_TREE_ELEM_GET
> +#error "MEMTX_TREE_ELEM_GET must be defined"
> +#endif
> +
> +#ifndef MEMTX_TREE_KEY_GET
> +#error "MEMTX_TREE_KEY_GET must be defined"
> +#endif

Please add a comment to each of the macros describing what it is
supposed to do.

>  
>  /**
> - * BPS tree element vs key comparator.
> - * Defined in header in order to allow compiler to inline it.
> - * @param tuple - tuple to compare.
> - * @param key_data - key to compare with.
> - * @param def - key definition.
> - * @retval 0  if tuple == key in terms of def.
> - * @retval <0 if tuple < key in terms of def.
> - * @retval >0 if tuple > key in terms of def.
> + * The size of the biggest memtx tree iterator. Used with
> + * mempool_create. This is the size of the block that will be
> + * allocated for each iterator.
>   */
> -static int
> -memtx_tree_compare_key(const struct tuple *tuple,
> -		       const struct memtx_tree_key_data *key_data,
> -		       struct key_def *def)
> -{
> -	return tuple_compare_with_key(tuple, key_data->key,
> -				      key_data->part_count, def);
> -}
> +#define MEMTX_TREE_ITERATOR_SIZE (152)

Take a look at struct memtx_engine:

	/** Memory pool for tree index iterator. */
	struct mempool tree_iterator_pool;
	/** Memory pool for rtree index iterator. */
	struct mempool rtree_iterator_pool;
	/** Memory pool for hash index iterator. */
	struct mempool hash_iterator_pool;
	/** Memory pool for bitset index iterator. */
	struct mempool bitset_iterator_pool;

This looks ugly. Let's use this trick with static iterator size for all
index types. Please do it in a separate patch.

>  
> -#define BPS_TREE_NAME memtx_tree
> +#define bps_tree_elem_t memtx_tree_elem
> +#define bps_tree_key_t memtx_tree_key *
> +#define bps_tree_arg_t struct key_def *
> +#define BPS_TREE_NAME CONCAT3(MEMTX_TREE_NAME, _, tree)
>  #define BPS_TREE_BLOCK_SIZE (512)
>  #define BPS_TREE_EXTENT_SIZE MEMTX_EXTENT_SIZE
> -#define BPS_TREE_COMPARE(a, b, arg) tuple_compare(a, b, arg)
> -#define BPS_TREE_COMPARE_KEY(a, b, arg) memtx_tree_compare_key(a, b, arg)
> -#define bps_tree_elem_t struct tuple *
> -#define bps_tree_key_t struct memtx_tree_key_data *
> -#define bps_tree_arg_t struct key_def *
> +#define BPS_TREE_COMPARE(a, b, arg) MEMTX_TREE_ELEM_CMP(&a, &b, arg)
> +#define BPS_TREE_COMPARE_KEY(a, b, arg) MEMTX_TREE_ELEM_WITH_KEY_CMP(&a, b, arg)
> +#define BPS_TREE_NO_DEBUG
>  
>  #include "salad/bps_tree.h"
>  
> +#undef bps_tree_elem_t
> +#undef bps_tree_key_t
> +#undef bps_tree_arg_t
>  #undef BPS_TREE_NAME
>  #undef BPS_TREE_BLOCK_SIZE
>  #undef BPS_TREE_EXTENT_SIZE
>  #undef BPS_TREE_COMPARE
>  #undef BPS_TREE_COMPARE_KEY
> -#undef bps_tree_elem_t
> -#undef bps_tree_key_t
> -#undef bps_tree_arg_t
> +#undef BPS_TREE_NO_DEBUG
> +
> +#define memtx_tree CONCAT3(MEMTX_TREE_NAME, _, tree)
> +#define _tree_api_name(postfix) CONCAT5(MEMTX_TREE_NAME, _, tree, _, postfix)

Why not _api_name?

> +#define memtx_tree_iterator _tree_api_name(iterator)
> +#define memtx_tree_iterator_is_invalid _tree_api_name(iterator_is_invalid)
> +#define memtx_tree_iterator_first _tree_api_name(iterator_first)
> +#define memtx_tree_iterator_last _tree_api_name(iterator_last)
> +#define memtx_tree_iterator_get_elem _tree_api_name(iterator_get_elem)
> +#define memtx_tree_iterator_next _tree_api_name(iterator_next)
> +#define memtx_tree_iterator_prev _tree_api_name(iterator_prev)
> +#define memtx_tree_iterator_freeze _tree_api_name(iterator_freeze)
> +#define memtx_tree_iterator_destroy _tree_api_name(iterator_destroy)
> +#define memtx_tree_create _tree_api_name(create)
> +#define memtx_tree_build _tree_api_name(build)
> +#define memtx_tree_destroy _tree_api_name(destroy)
> +#define memtx_tree_find _tree_api_name(find)
> +#define memtx_tree_insert _tree_api_name(insert)
> +#define memtx_tree_delete _tree_api_name(delete)
> +#define memtx_tree_size _tree_api_name(size)
> +#define memtx_tree_mem_used _tree_api_name(mem_used)
> +#define memtx_tree_random _tree_api_name(random)
> +#define memtx_tree_invalid_iterator _tree_api_name(invalid_iterator)
> +#define memtx_tree_lower_bound _tree_api_name(lower_bound)
> +#define memtx_tree_upper_bound _tree_api_name(upper_bound)
> +#define memtx_tree_lower_bound_elem _tree_api_name(lower_bound_elem)
> +#define memtx_tree_upper_bound_elem _tree_api_name(upper_bound_elem)
> +
> +#undef _api_name

BPS tree should undef all macros it defines on its own. Please fix it in
a separate patch.

> +#define _api_name(postfix) CONCAT3(MEMTX_TREE_NAME, _, postfix)
> +#define memtx_tree_index _api_name(index)
> +#define memtx_tree_qcompare _api_name(qcompare)
> +#define tree_iterator _api_name(iterator)
> +#define tree_iterator_free _api_name(iterator_free)
> +#define tree_iterator_cast _api_name(iterator_cast)
> +#define tree_iterator_dummie _api_name(iterator_dummie)
> +#define tree_iterator_next _api_name(iterator_next)
> +#define tree_iterator_prev _api_name(iterator_prev)
> +#define tree_iterator_next_equal _api_name(iterator_next_equal)
> +#define tree_iterator_prev_equal _api_name(iterator_prev_equal)
> +#define tree_iterator_set_next_method _api_name(iterator_set_next_method)
> +#define tree_iterator_start _api_name(iterator_start)
> +#define memtx_tree_index_cmp_def _api_name(index_cmp_def)
> +#define memtx_tree_index_free _api_name(index_free)
> +#define memtx_tree_index_gc_run _api_name(index_gc_run)
> +#define memtx_tree_index_gc_free _api_name(index_gc_free)
> +#define memtx_tree_index_gc_vtab _api_name(index_gc_vtab)
> +#define memtx_tree_index_destroy _api_name(index_destroy)
> +#define memtx_tree_index_update_def _api_name(index_update_def)
> +#define memtx_tree_index_depends_on_pk _api_name(index_depends_on_pk)
> +#define memtx_tree_index_size _api_name(index_size)
> +#define memtx_tree_index_bsize _api_name(index_bsize)
> +#define memtx_tree_index_random _api_name(index_random)
> +#define memtx_tree_index_count _api_name(index_count)
> +#define memtx_tree_index_get _api_name(index_get)
> +#define memtx_tree_index_insert_tuple _api_name(index_insert_tuple)
> +#define memtx_tree_index_delete_tuple _api_name(index_delete_tuple)
> +#define memtx_tree_index_replace _api_name(index_replace)
> +#define memtx_tree_index_create_iterator _api_name(index_create_iterator)
> +#define memtx_tree_index_begin_build _api_name(index_begin_build)
> +#define memtx_tree_index_build_next _api_name(index_build_next)
> +#define memtx_tree_index_reserve _api_name(index_reserve)
> +#define memtx_tree_index_end_build _api_name(index_end_build)
> +#define tree_snapshot_iterator _api_name(snapshot_iterator)
> +#define tree_snapshot_iterator_free _api_name(snapshot_iterator_free)
> +#define tree_snapshot_iterator_next _api_name(snapshot_iterator_next)
> +#define memtx_tree_index_create_snapshot_iterator\
> +	_api_name(index_create_snapshot_iterator)
> +#define memtx_tree_index_vtab _api_name(index_vtab)
> +#define memtx_tree_index_new _api_name(index_new)

I'd undef _api_name right here, because we don't need it anywhere else.

>  
>  struct memtx_tree_index {
>  	struct index base;
> -	struct memtx_tree tree;
> -	struct tuple **build_array;
> +	memtx_tree_elem *build_array;
>  	size_t build_array_size, build_array_alloc_size;
>  	struct memtx_gc_task gc_task;
> +	struct memtx_tree tree;

Nit: pointless change (moving 'tree' member).

>  	struct memtx_tree_iterator gc_iterator;
>  };
>  
> @@ -102,8 +186,8 @@ struct memtx_tree_index {
>  static int
>  memtx_tree_qcompare(const void* a, const void *b, void *c)
>  {
> -	return tuple_compare(*(struct tuple **)a,
> -		*(struct tuple **)b, (struct key_def *)c);
> +	return MEMTX_TREE_ELEM_CMP((memtx_tree_elem *)a,
> +				   (memtx_tree_elem *)b, c);
>  }
>  
>  /* {{{ MemtxTree Iterators ****************************************/
> @@ -113,17 +197,21 @@ struct tree_iterator {
>  	struct index_def *index_def;
>  	struct memtx_tree_iterator tree_iterator;
>  	enum iterator_type type;
> -	struct memtx_tree_key_data key_data;
> -	struct tuple *current_tuple;
> +	memtx_tree_key key_data;
> +	memtx_tree_elem current;
>  	/** Memory pool the iterator was allocated from. */
>  	struct mempool *pool;
>  };
>  
> +static_assert(sizeof(struct tree_iterator) <= MEMTX_TREE_ITERATOR_SIZE,
> +	      "tree_iterator must be less or equal than "
> +	      "MEMTX_TREE_ITERATOR_SIZE");
> +
>  static void
>  tree_iterator_free(struct iterator *iterator);
>  
>  static inline struct tree_iterator *
> -tree_iterator(struct iterator *it)
> +tree_iterator_cast(struct iterator *it)
>  {
>  	assert(it->free == tree_iterator_free);
>  	return (struct tree_iterator *) it;
> @@ -132,9 +220,10 @@ tree_iterator(struct iterator *it)
>  static void
>  tree_iterator_free(struct iterator *iterator)
>  {
> -	struct tree_iterator *it = tree_iterator(iterator);
> -	if (it->current_tuple != NULL)
> -		tuple_unref(it->current_tuple);
> +	struct tree_iterator *it = tree_iterator_cast(iterator);
> +	struct tuple *tuple = MEMTX_TREE_ELEM_GET(&it->current);
> +	if (tuple != NULL)
> +		tuple_unref(tuple);
>  	mempool_free(it->pool, it);
>  }
>  
> @@ -149,25 +238,28 @@ tree_iterator_dummie(struct iterator *iterator, struct tuple **ret)
>  static int
>  tree_iterator_next(struct iterator *iterator, struct tuple **ret)
>  {
> -	struct tuple **res;
> -	struct tree_iterator *it = tree_iterator(iterator);
> -	assert(it->current_tuple != NULL);
> -	struct tuple **check = memtx_tree_iterator_get_elem(it->tree, &it->tree_iterator);
> -	if (check == NULL || *check != it->current_tuple)
> +	struct tree_iterator *it = tree_iterator_cast(iterator);
> +	assert(MEMTX_TREE_ELEM_GET(&it->current) != NULL);
> +	memtx_tree_elem *check =
> +		memtx_tree_iterator_get_elem(it->tree, &it->tree_iterator);
> +	if (check == NULL ||
> +	    MEMTX_TREE_ELEM_GET(check) != MEMTX_TREE_ELEM_GET(&it->current)) {

AFAIU this check isn't quite correct: we want to make sure that
it->current and check refer to the same tree element. So in case
of a multikey index it isn't enough to just check the tuples they
refer to - you also need to check the key offsets.

> diff --git a/src/box/memtx_tree_decl.c b/src/box/memtx_tree_decl.c
> new file mode 100644
> index 000000000..03e0e0ed7
> --- /dev/null
> +++ b/src/box/memtx_tree_decl.c
> @@ -0,0 +1,84 @@
> +/*
> + * Copyright 2010-2019, Tarantool AUTHORS, please see AUTHORS file.
> + *
> + * Redistribution and use in source and binary forms, with or
> + * without modification, are permitted provided that the following
> + * conditions are met:
> + *
> + * 1. Redistributions of source code must retain the above
> + *    copyright notice, this list of conditions and the
> + *    following disclaimer.
> + *
> + * 2. Redistributions in binary form must reproduce the above
> + *    copyright notice, this list of conditions and the following
> + *    disclaimer in the documentation and/or other materials
> + *    provided with the distribution.
> + *
> + * THIS SOFTWARE IS PROVIDED BY <COPYRIGHT HOLDER> ``AS IS'' AND
> + * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
> + * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
> + * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
> + * <COPYRIGHT HOLDER> OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
> + * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
> + * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
> + * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
> + * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
> + * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
> + * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
> + * THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
> + * SUCH DAMAGE.
> + */
> +#include <stdbool.h>
> +#include <stdint.h>
> +#include "tuple_compare.h"
> +#include "memtx_tree.h"
> +
> +/* {{{ Memtx tree of tuples class. ******************************/
> +
> +/** Struct that is used as a key in BPS tree definition. */
> +struct memtx_tuple_tree_key_data {
> +	/** Sequence of msgpacked search fields. */
> +	const char *key;
> +	/** Number of msgpacked search fields. */
> +	uint32_t part_count;
> +};
> +
> +#define MEMTX_TREE_NAME memtx_tuple_tree

I don't quite like the name, because all memtx indexes store tuples,
eventually. May be, memtx_simple_tree or memtx_basic_tree?

> +#define memtx_tree_elem struct tuple *
> +#define memtx_tree_key struct memtx_tuple_tree_key_data
> +#define MEMTX_TREE_ELEM_CMP(elem_a_ptr, elem_b_ptr, key_def)			\
> +	tuple_compare(*elem_a_ptr, *elem_b_ptr, key_def)
> +#define MEMTX_TREE_ELEM_WITH_KEY_CMP(elem_ptr, key_ptr, key_def)		\
> +	tuple_compare_with_key(*elem_ptr, (key_ptr)->key,			\
> +			       (key_ptr)->part_count, key_def)
> +#define MEMTX_TREE_ELEM_SET(elem_ptr, tuple, key_def)				\
> +	({(void)key_def; *elem_ptr = tuple;})
> +#define MEMTX_TREE_KEY_SET(key_ptr, key_val, part_count_val, key_def)		\
> +	({(void)key_def; (key_ptr)->key = key_val;				\
> +	 (key_ptr)->part_count = part_count_val;})
> +#define MEMTX_TREE_ELEM_GET(elem_ptr) (*(elem_ptr))
> +#define MEMTX_TREE_KEY_GET(key_ptr, part_count_ptr)				\
> +	({*part_count_ptr = (key_ptr)->part_count; (key_ptr)->key;})
> +
> +#include "memtx_tree.c"
> +
> +#undef memtx_tree_key
> +#undef memtx_tree_elem
> +#undef MEMTX_TREE_KEY_GET
> +#undef MEMTX_TREE_ELEM_GET
> +#undef MEMTX_TREE_KEY_SET
> +#undef MEMTX_TREE_ELEM_SET
> +#undef MEMTX_TREE_ELEM_WITH_KEY_CMP
> +#undef MEMTX_TREE_ELEM_CMP

> +#undef MEMTX_TREE_ELEM_EQUAL

This one is never defined.

> +#undef memtx_tree_key
> +#undef memtx_tree_elem

You undef those twice.

> +#undef MEMTX_TREE_NAME
> +
> +/* }}} */
> +
> +struct index *
> +memtx_tree_index_new(struct memtx_engine *memtx, struct index_def *def)
> +{
> +	return memtx_tuple_tree_index_new(memtx, def);
> +}

Re: [tarantool-patches] Re: [PATCH v2 4/4] box: introduce tuple compare hint for string index

[Vladimir Davydov]

On Tue, Feb 19, 2019 at 06:02:55PM +0300, Kirill Shcherbatov wrote:
> diff --git a/src/box/memtx_tree_decl.c b/src/box/memtx_tree_decl.c
> index 084a0594f..55016148b 100644
> --- a/src/box/memtx_tree_decl.c
> +++ b/src/box/memtx_tree_decl.c
> @@ -77,8 +77,133 @@ struct memtx_tuple_tree_key_data {
>  
>  /* }}} */
>  
> +/* {{{ Memtx hinted and hint_only tree class. *******************/

There's no hint_only tree anymore. Please update the comments.

> +
> +/**
> + * Struct that is used as a key in BPS tree definition in
> + * memtx_hint_only_tree and memtx_hinted_tree.
> +*/
> +struct memtx_hinted_tree_key_data {
> +	/** Sequence of msgpacked search fields. */
> +	const char *key;
> +	/** Number of msgpacked search fields. */
> +	uint32_t part_count;
> +	/**
> +	 * Compare hint. Is calculated automatically on 'set'

Comparison hint. 'Is' isn't necessary - could be simply Calculated ...

> +	 * operation with memtx_hinted_tree_key_data_set().
> +	 */
> +	uint64_t hint;
> +};
> +
> +/**
> + * Struct that is used as a key in BPS tree definition in
> + * memtx_hint_only_tree and memtx_hinted_tree.
> + */
> +struct memtx_hinted_tree_data {
> +	/** Tuple this node is representing. */

represents

> +	struct tuple *tuple;
> +	/**
> +	 * Compare hint. Is calculated automatically on 'set'
> +	 * operation with memtx_hinted_tree_data_set().
> +	 */
> +	uint64_t hint;
> +};
> +
> +/**
> + * Compare memtx_hinted_tree records.
> + */
> +static int
> +memtx_hinted_tree_data_cmp(struct memtx_hinted_tree_data *a,
> +			   struct memtx_hinted_tree_data *b,
> +			   struct key_def *key_def)
> +{
> +	if (a->hint != b->hint)
> +		return a->hint < b->hint ? -1 : 1;
> +	return tuple_compare(a->tuple, b->tuple, key_def);
> +}
> +
> +/**
> + * Compare memtx_hinted_tree record with key.
> + */
> +static int
> +memtx_hinted_tree_data_cmp_with_key(struct memtx_hinted_tree_data *a,
> +				    struct memtx_hinted_tree_key_data *key,
> +				    struct key_def *key_def)
> +{
> +	if (a->hint != key->hint)
> +		return a->hint < key->hint ? -1 : 1;
> +	return tuple_compare_with_key(a->tuple, key->key, key->part_count,
> +				      key_def);
> +}
> +
> +/**
> + * Initialize memtx_hinted_tree or memtx_hint_only_tree record
> + * with tuple and recalculate internal hint field.
> + */
> +static void
> +memtx_hinted_tree_data_set(struct memtx_hinted_tree_data *data,
> +			   struct tuple *tuple, struct key_def *key_def)
> +{
> +	data->tuple = tuple;
> +	data->hint = tuple_hint(tuple, key_def);
> +}
> +
> +/**
> + * Initialize memtx_hinted_tree or memtx_hint_only_tree key with
> + * key raw and part count and recalculate internal hint field.
> + */
> +static void
> +memtx_hinted_tree_key_data_set(struct memtx_hinted_tree_key_data *key_data,
> +			       const char *key, uint32_t part_count,
> +			       struct key_def *key_def)

All these functions aren't used anywhere except in MEMTX_TREE_ macros,
and they're pretty short. Worth inlining them there?

> +{
> +	key_data->key = key;
> +	key_data->part_count = part_count;
> +	key_data->hint = key != NULL && part_count > 0 ?

No need to check both part_count and key. Either of them is enough.

> +			 key_hint(key, key_def) : 0;
> +}
> +
> +#define MEMTX_TREE_NAME memtx_hinted_tree
> +#define memtx_tree_elem struct memtx_hinted_tree_data
> +#define memtx_tree_key struct memtx_hinted_tree_key_data

> +#define MEMTX_TREE_ELEM_EQUAL(elem_a_ptr, elem_b_ptr)				\
> +	((elem_a_ptr)->tuple == (elem_b_ptr)->tuple)

This macro isn't required as far as I recall.

> +#define MEMTX_TREE_ELEM_CMP(elem_a_ptr, elem_b_ptr, key_def)			\
> +	memtx_hinted_tree_data_cmp(elem_a_ptr, elem_b_ptr, key_def)
> +#define MEMTX_TREE_ELEM_WITH_KEY_CMP(elem_ptr, key_ptr, key_def)		\
> +	memtx_hinted_tree_data_cmp_with_key(elem_ptr, key_ptr, key_def)
> +#define MEMTX_TREE_ELEM_SET(elem_ptr, tuple, key_def)				\
> +	memtx_hinted_tree_data_set(elem_ptr, tuple, key_def)
> +#define MEMTX_TREE_KEY_SET(key_ptr, key_val, part_count_val, key_def)		\
> +	memtx_hinted_tree_key_data_set(key_ptr, key_val, part_count_val,	\
> +				       key_def)
> +#define MEMTX_TREE_ELEM_GET(elem_ptr) ((elem_ptr)->tuple)
> +#define MEMTX_TREE_KEY_GET(key_ptr, part_count_ptr)				\
> +	({*part_count_ptr = (key_ptr)->part_count; (key_ptr)->key;})
> +
> +#include "memtx_tree_impl.h"
> +
> +#undef memtx_tree_key
> +#undef memtx_tree_elem
> +#undef MEMTX_TREE_KEY_GET
> +#undef MEMTX_TREE_ELEM_GET
> +#undef MEMTX_TREE_KEY_SET
> +#undef MEMTX_TREE_ELEM_SET
> +#undef MEMTX_TREE_ELEM_WITH_KEY_CMP
> +#undef MEMTX_TREE_ELEM_CMP
> +#undef MEMTX_TREE_ELEM_EQUAL
> +#undef memtx_tree_key
> +#undef memtx_tree_elem
> +#undef MEMTX_TREE_NAME
> +
> +/* }}} */
> +
>  struct index *
>  memtx_tree_index_new(struct memtx_engine *memtx, struct index_def *def)
>  {
> +	if (def->cmp_def->parts->type == FIELD_TYPE_STRING ||
> +	    def->cmp_def->parts->type == FIELD_TYPE_UNSIGNED ||
> +	    def->cmp_def->parts->type == FIELD_TYPE_INTEGER)
> +		return memtx_hinted_tree_index_new(memtx, def);
>  	return memtx_tuple_tree_index_new(memtx, def);
>  }
> diff --git a/src/box/tuple_compare.cc b/src/box/tuple_compare.cc
> index ded802c7d..5845235ff 100644
> --- a/src/box/tuple_compare.cc
> +++ b/src/box/tuple_compare.cc
> @@ -1321,4 +1321,189 @@ tuple_compare_with_key_create(const struct key_def *def)
>  	       compare_with_key_slowpath_funcs[cmp_func_idx];
>  }

I think all the hints should be defined in new files tuple_hint.{h,cc}

>  
> +static uint64_t
> +key_hint_default(const char *key, struct key_def *key_def)
> +{
> +	(void)key;
> +	(void)key_def;
> +	return 0;
> +}
> +
> +static uint64_t
> +tuple_hint_default(const struct tuple *tuple, struct key_def *key_def)
> +{
> +	(void)tuple;
> +	(void)key_def;
> +	return 0;
> +}
> +
> +template<bool is_nullable>

I doubt we need to use templates here, but OK, let them be.

> +static uint64_t
> +key_hint_uint(const char *key, struct key_def *key_def)
> +{
> +	(void)key_def;
> +	assert(key_part_is_nullable(key_def->parts) == is_nullable);
> +	if (is_nullable && mp_typeof(*key) == MP_NIL)
> +		return 0;
> +	assert(mp_typeof(*key) == MP_UINT);
> +	uint64_t val = mp_decode_uint(&key);
> +	if (val > INT64_MAX)
> +		return INT64_MAX;
> +	return val - (uint64_t)INT64_MIN;
> +}
> +
> +template<bool is_nullable>
> +static uint64_t
> +tuple_hint_uint(const struct tuple *tuple, struct key_def *key_def)
> +{
> +	assert(key_part_is_nullable(key_def->parts) == is_nullable);
> +	const char *field = tuple_field_by_part(tuple, key_def->parts);
> +	if (is_nullable && field == NULL)
> +		return 0;
> +	return key_hint_uint<is_nullable>(field, key_def);
> +}
> +
> +template<bool is_nullable>
> +static uint64_t
> +key_hint_int(const char *key, struct key_def *key_def)
> +{
> +	assert(key_part_is_nullable(key_def->parts) == is_nullable);
> +	if (is_nullable && mp_typeof(*key) == MP_NIL)
> +		return 0;
> +	if (mp_typeof(*key) == MP_UINT) {
> +		return key_hint_uint<is_nullable>(key, key_def);
> +	} else {

> +		assert(key_def->parts->type == FIELD_TYPE_INTEGER);

This assertion should be in the beginning of this function, no?

Please also add assertions checking part->type to other hint functions.

> +		assert(mp_typeof(*key) == MP_INT);
> +		int64_t val = mp_decode_int(&key);
> +		return (uint64_t)val - (uint64_t)INT64_MIN;
> +	}
> +}
> +
> +template<bool is_nullable>
> +static uint64_t
> +tuple_hint_int(const struct tuple *tuple, struct key_def *key_def)
> +{
> +	assert(key_part_is_nullable(key_def->parts) == is_nullable);
> +	const char *field = tuple_field_by_part(tuple, key_def->parts);
> +	if (is_nullable && field == NULL)
> +		return 0;
> +	return key_hint_int<is_nullable>(field, key_def);
> +}
> +
> +template<bool is_nullable>
> +static uint64_t
> +key_hint_string(const char *key, struct key_def *key_def)
> +{
> +	(void)key_def;
> +	assert(key_part_is_nullable(key_def->parts) == is_nullable);
> +	if (is_nullable && mp_typeof(*key) == MP_NIL)
> +		return 0;
> +	assert(key_def->parts->type == FIELD_TYPE_STRING);
> +	assert(mp_typeof(*key) == MP_STR);
> +	uint32_t len;
> +	const unsigned char *str =
> +		(const unsigned char *)mp_decode_str(&key, &len);
> +	uint64_t result = 0;
> +	/*
> +	 * Map the sequence of characters in the hint's bytes in
> +	 * the reverse order: the first character will be mapped
> +	 * in the highest byte of the number, etc.
> +	 * One additional bit encodes the presence of the next
> +	 * sign.
> +	 * 0bCHARBYTEU CHARBYTEU CHARBYTEU ... CHARBYTE0
> +	 * The sequence constructed in this way provides a
> +	 * comparison transitivity of strings no longer than 7
> +	 * bytes.

Still I don't understand why we need this transformation and why simply
using a sequence of bytes constituting the string isn't enough. Could
you give an example?

> +	 */
> +	uint32_t process_len = MIN(len, 7);
> +	for (uint32_t i = 0; i < process_len; i++) {
> +		result <<= 9;
> +		result |= 0x100;
> +		result |= str[i];
> +	}
> +	/*
> +	 * If the length of the string is less than the 64-bit
> +	 * hint can accommodate, the insignificant positions are
> +	 * filled with 0.
> +	 */
> +	result <<= 9 * (7 - process_len);
> +	return result;
> +}
> +
> +template<bool is_nullable>
> +static uint64_t
> +tuple_hint_string(const struct tuple *tuple, struct key_def *key_def)
> +{
> +	assert(key_part_is_nullable(key_def->parts) == is_nullable);
> +	const char *field = tuple_field_by_part(tuple, key_def->parts);
> +	if (is_nullable && field == NULL)
> +		return 0;
> +	return key_hint_string<is_nullable>(field, key_def);
> +}
> +
> +template<bool is_nullable>
> +static uint64_t
> +key_hint_string_coll(const char *key, struct key_def *key_def)
> +{
> +	assert(key_part_is_nullable(key_def->parts) == is_nullable);
> +	if (is_nullable && mp_typeof(*key) == MP_NIL)
> +		return 0;
> +	assert(key_def->parts->type == FIELD_TYPE_STRING);
> +	assert(mp_typeof(*key) == MP_STR);
> +	assert(key_def->parts->coll != NULL);
> +	uint32_t len;
> +	const char *str = mp_decode_str(&key, &len);
> +	return key_def->parts->coll->hint(str, len, key_def->parts->coll);
> +}
> +
> +template<bool is_nullable>
> +static uint64_t
> +tuple_hint_string_coll(const struct tuple *tuple, struct key_def *key_def)
> +{
> +	assert(key_part_is_nullable(key_def->parts) == is_nullable);
> +	const char *field = tuple_field_by_part(tuple, key_def->parts);
> +	if (is_nullable && field == NULL)
> +		return 0;
> +	return key_hint_string_coll<is_nullable>(field, key_def);
> +}
> +
> +void
> +tuple_hint_set(struct key_def *def)

Should be called key_def_set_hint_func. Please rename.

> +{
> +	def->key_hint = key_hint_default;
> +	def->tuple_hint = tuple_hint_default;
> +	bool is_nullable = key_part_is_nullable(def->parts);
> +	if (def->parts->type == FIELD_TYPE_STRING && def->parts->coll != NULL &&
> +	    def->parts->coll->type != COLL_TYPE_BINARY) {
> +		def->key_hint = is_nullable ? key_hint_string_coll<true> :
> +					      key_hint_string_coll<false>;
> +		def->tuple_hint = is_nullable ? tuple_hint_string_coll<true> :
> +						tuple_hint_string_coll<false>;
> +		return;
> +	}
> +	switch (def->parts->type) {
> +	case FIELD_TYPE_UNSIGNED:
> +		def->key_hint = is_nullable ? key_hint_uint<true> :
> +					      key_hint_uint<false>;
> +		def->tuple_hint = is_nullable ? tuple_hint_uint<true> :
> +						tuple_hint_uint<false>;
> +		break;
> +	case FIELD_TYPE_INTEGER:
> +		def->key_hint = is_nullable ? key_hint_int<true> :
> +					      key_hint_int<false>;
> +		def->tuple_hint = is_nullable ? tuple_hint_int<true> :
> +						tuple_hint_int<false>;
> +		break;
> +	case FIELD_TYPE_STRING:
> +		def->key_hint = is_nullable ? key_hint_string<true> :
> +					      key_hint_string<false>;
> +		def->tuple_hint = is_nullable ? tuple_hint_string<true> :
> +						tuple_hint_string<false>;
> +		break;
> +	default:
> +		break;
> +	};
> +}