Hi,
 
Thanks for the patch!
 
LGTM, i checked for the number of compilers that if with the templated
agrument is being processed at the compile time so that there are no jumps
in asm code.
 
What i think is needed is the enum like the following:
enum {
        NOT_HINTED =  0 ,
        HINTED =  1 ,
};
 
to avoid using <0> & <1>. If needed i can push such patch to the branch. 
>Понедельник, 19 октября 2020, 12:52 +03:00 от Aleksandr Lyapunov <alyapunov@tarantool.org>:
> 
>Since 9fba29abb4e05babb9b23b4413bd8083f0fba933 (memtx: introduce tuple
>compare hint) memtx tree key data (indexes) started to contain extra 8
>bytes as a hint. Now it is optional and can be turned off in an index
>options with "hint = false" entry.
>
>Closes #4927
>
>@TarantoolBot document
>Title: memtx: optional tuple compare hints
>Update the documentation for an index creation to reflect that there is
>now an option to turn off hints for the index.
>---
> src/box/index_def.c | 2 +
> src/box/index_def.h | 6 +
> src/box/lua/schema.lua | 53 ++++
> src/box/lua/space.cc | 7 +
> src/box/memtx_engine.c | 2 +
> src/box/memtx_tree.cc | 599 ++++++++++++++++++++++++------------
> src/lib/salad/bps_tree.h | 19 ++
> test/box/alter.result | 103 ++++++-
> test/box/alter.test.lua | 34 ++
> test/box/errinj.result | 3 +-
> test/box/tree_pk.result | 314 +++++++++++++++++++
> test/box/tree_pk.test.lua | 115 +++++++
> test/box/tree_pk_multipart.result | 153 +++++++++
> test/box/tree_pk_multipart.test.lua | 64 ++++
> 14 files changed, 1269 insertions(+), 205 deletions(-)
>
>diff --git a/src/box/index_def.c b/src/box/index_def.c
>index 9802961..79394b8 100644
>--- a/src/box/index_def.c
>+++ b/src/box/index_def.c
>@@ -51,6 +51,7 @@ const struct index_opts index_opts_default = {
>  /* .lsn = */ 0,
>  /* .stat = */ NULL,
>  /* .func = */ 0,
>+ /* .hint = */ true,
> };
> 
> const struct opt_def index_opts_reg[] = {
>@@ -66,6 +67,7 @@ const struct opt_def index_opts_reg[] = {
>  OPT_DEF("lsn", OPT_INT64, struct index_opts, lsn),
>  OPT_DEF("func", OPT_UINT32, struct index_opts, func_id),
>  OPT_DEF_LEGACY("sql"),
>+ OPT_DEF("hint", OPT_BOOL, struct index_opts, hint),
>  OPT_END,
> };
> 
>diff --git a/src/box/index_def.h b/src/box/index_def.h
>index d928b23..2180a69 100644
>--- a/src/box/index_def.h
>+++ b/src/box/index_def.h
>@@ -165,6 +165,10 @@ struct index_opts {
>  struct index_stat *stat;
>  /** Identifier of the functional index function. */
>  uint32_t func_id;
>+ /**
>+ * Use hint optimization for tree index.
>+ */
>+ bool hint;
> };
> 
> extern const struct index_opts index_opts_default;
>@@ -211,6 +215,8 @@ index_opts_cmp(const struct index_opts *o1, const struct index_opts *o2)
>  return o1->bloom_fpr < o2->bloom_fpr ? -1 : 1;
>  if (o1->func_id != o2->func_id)
>  return o1->func_id - o2->func_id;
>+ if (o1->hint != o2->hint)
>+ return o1->hint - o2->hint;
>  return 0;
> }
> 
>diff --git a/src/box/lua/schema.lua b/src/box/lua/schema.lua
>index 1131af7..9cc1289 100644
>--- a/src/box/lua/schema.lua
>+++ b/src/box/lua/schema.lua
>@@ -1000,8 +1000,31 @@ local index_options = {
>     page_size = 'number',
>     bloom_fpr = 'number',
>     func = 'number, string',
>+ hint = 'boolean',
> }
> 
>+local function jsonpaths_from_idx_parts(parts)
>+ local paths = {}
>+
>+ for _, part in pairs(parts) do
>+ if type(part.path) == 'string' then
>+ table.insert(paths, part.path)
>+ end
>+ end
>+
>+ return paths
>+end
>+
>+local function is_multikey_index(parts)
>+ for _, path in pairs(jsonpaths_from_idx_parts(parts)) do
>+ if path:find('[*]', 1, true) then
>+ return true
>+ end
>+ end
>+
>+ return false
>+end
>+
> --
> -- check_param_table() template for alter index,
> -- includes all index options.
>@@ -1076,6 +1099,15 @@ box.schema.index.create = function(space_id, name, options)
>         options_defaults = {}
>     end
>     options = update_param_table(options, options_defaults)
>+ if options.hint and
>+ (options.type ~= 'tree' or box.space[space_id].engine ~= 'memtx') then
>+ box.error(box.error.MODIFY_INDEX, name, space.name,
>+ "hint is only reasonable with memtx tree index")
>+ end
>+ if options.hint and options.func then
>+ box.error(box.error.MODIFY_INDEX, name, space.name,
>+ "functional index can't use hints")
>+ end
> 
>     local _index = box.space[box.schema.INDEX_ID]
>     local _vindex = box.space[box.schema.VINDEX_ID]
>@@ -1115,6 +1147,7 @@ box.schema.index.create = function(space_id, name, options)
>             run_size_ratio = options.run_size_ratio,
>             bloom_fpr = options.bloom_fpr,
>             func = options.func,
>+ hint = options.hint,
>     }
>     local field_type_aliases = {
>         num = 'unsigned'; -- Deprecated since 1.7.2
>@@ -1135,6 +1168,10 @@ box.schema.index.create = function(space_id, name, options)
>     if parts_can_be_simplified then
>         parts = simplify_index_parts(parts)
>     end
>+ if options.hint and is_multikey_index(parts) then
>+ box.error(box.error.MODIFY_INDEX, name, space.name,
>+ "multikey index can't use hints")
>+ end
>     if index_opts.func ~= nil and type(index_opts.func) == 'string' then
>         index_opts.func = func_id_by_name(index_opts.func)
>     end
>@@ -1253,6 +1290,17 @@ box.schema.index.alter = function(space_id, index_id, options)
>             index_opts[k] = options[k]
>         end
>     end
>+ if options.hint and
>+ (options.type ~= 'tree' or box.space[space_id].engine ~= 'memtx') then
>+ box.error(box.error.MODIFY_INDEX, space.index[index_id].name,
>+ space.name,
>+ "hint is only reasonable with memtx tree index")
>+ end
>+ if options.hint and options.func then
>+ box.error(box.error.MODIFY_INDEX, space.index[index_id].name,
>+ space.name,
>+ "functional index can't use hints")
>+ end
>     if options.parts then
>         local parts_can_be_simplified
>         parts, parts_can_be_simplified =
>@@ -1262,6 +1310,11 @@ box.schema.index.alter = function(space_id, index_id, options)
>             parts = simplify_index_parts(parts)
>         end
>     end
>+ if options.hint and is_multikey_index(parts) then
>+ box.error(box.error.MODIFY_INDEX, space.index[index_id].name,
>+ space.name,
>+ "multikey index can't use hints")
>+ end
>     if index_opts.func ~= nil and type(index_opts.func) == 'string' then
>         index_opts.func = func_id_by_name(index_opts.func)
>     end
>diff --git a/src/box/lua/space.cc b/src/box/lua/space.cc
>index 177c588..1ea993c 100644
>--- a/src/box/lua/space.cc
>+++ b/src/box/lua/space.cc
>@@ -344,6 +344,13 @@ lbox_fillspace(struct lua_State *L, struct space *space, int i)
>  lua_pushnumber(L, index_opts->dimension);
>  lua_setfield(L, -2, "dimension");
>  }
>+ if (space_is_memtx(space) && index_def->type == TREE) {
>+ lua_pushboolean(L, index_opts->hint);
>+ lua_setfield(L, -2, "hint");
>+ } else {
>+ lua_pushnil(L);
>+ lua_setfield(L, -2, "hint");
>+ }
> 
>  if (index_opts->func_id > 0) {
>  lua_pushstring(L, "func");
>diff --git a/src/box/memtx_engine.c b/src/box/memtx_engine.c
>index  8147557 ..43000ba 100644
>--- a/src/box/memtx_engine.c
>+++ b/src/box/memtx_engine.c
>@@ -1398,6 +1398,8 @@ memtx_index_def_change_requires_rebuild(struct index *index,
>  return true;
>  if (old_def->opts.func_id != new_def->opts.func_id)
>  return true;
>+ if (old_def->opts.hint != new_def->opts.hint)
>+ return true;
> 
>  const struct key_def *old_cmp_def, *new_cmp_def;
>  if (index_depends_on_pk(index)) {
>diff --git a/src/box/memtx_tree.cc b/src/box/memtx_tree.cc
>index d3b993b..17d58c5 100644
>--- a/src/box/memtx_tree.cc
>+++ b/src/box/memtx_tree.cc
>@@ -45,23 +45,51 @@
> /**
>  * Struct that is used as a key in BPS tree definition.
>  */
>-struct memtx_tree_key_data {
>+struct memtx_tree_key_data_common {
>  /** Sequence of msgpacked search fields. */
>  const char *key;
>  /** Number of msgpacked search fields. */
>  uint32_t part_count;
>+};
>+
>+template <int USE_HINT>
>+struct memtx_tree_key_data;
>+
>+template <>
>+struct memtx_tree_key_data<0> : memtx_tree_key_data_common {
>+ static constexpr hint_t hint = HINT_NONE;
>+ void set_hint(hint_t) { assert(false); }
>+};
>+
>+template <>
>+struct memtx_tree_key_data<1> : memtx_tree_key_data_common {
>  /** Comparison hint, see tuple_hint(). */
>  hint_t hint;
>+ void set_hint(hint_t h) { hint = h; }
> };
> 
> /**
>  * Struct that is used as a elem in BPS tree definition.
>  */
>-struct memtx_tree_data {
>+struct memtx_tree_data_common {
>  /* Tuple that this node is represents. */
>  struct tuple *tuple;
>+};
>+
>+template <int USE_HINT>
>+struct memtx_tree_data;
>+
>+template <>
>+struct memtx_tree_data<0> : memtx_tree_data_common {
>+ static constexpr hint_t hint = HINT_NONE;
>+ void set_hint(hint_t) { assert(false); }
>+};
>+
>+template <>
>+struct memtx_tree_data<1> : memtx_tree_data<0> {
>  /** Comparison hint, see key_hint(). */
>  hint_t hint;
>+ void set_hint(hint_t h) { hint = h; }
> };
> 
> /**
>@@ -73,8 +101,8 @@ struct memtx_tree_data {
>  * @retval false - Otherwise.
>  */
> static bool
>-memtx_tree_data_is_equal(const struct memtx_tree_data *a,
>- const struct memtx_tree_data *b)
>+memtx_tree_data_is_equal(const struct memtx_tree_data_common *a,
>+ const struct memtx_tree_data_common *b)
> {
>  return a->tuple == b->tuple;
> }
>@@ -89,12 +117,28 @@ memtx_tree_data_is_equal(const struct memtx_tree_data *a,
>  (b)->part_count, (b)->hint, arg)
> #define BPS_TREE_IS_IDENTICAL(a, b) memtx_tree_data_is_equal(&a, &b)
> #define BPS_TREE_NO_DEBUG 1
>-#define bps_tree_elem_t struct memtx_tree_data
>-#define bps_tree_key_t struct memtx_tree_key_data *
> #define bps_tree_arg_t struct key_def *
> 
>+#define BPS_TREE_NAMESPACE NS_NO_HINT
>+#define bps_tree_elem_t struct memtx_tree_data<0>
>+#define bps_tree_key_t struct memtx_tree_key_data<0> *
>+
> #include "salad/bps_tree.h"
> 
>+#undef BPS_TREE_NAMESPACE
>+#undef bps_tree_elem_t
>+#undef bps_tree_key_t
>+
>+#define BPS_TREE_NAMESPACE NS_USE_HINT
>+#define bps_tree_elem_t struct memtx_tree_data<1>
>+#define bps_tree_key_t struct memtx_tree_key_data<1> *
>+
>+#include "salad/bps_tree.h"
>+
>+#undef BPS_TREE_NAMESPACE
>+#undef bps_tree_elem_t
>+#undef bps_tree_key_t
>+
> #undef BPS_TREE_NAME
> #undef BPS_TREE_BLOCK_SIZE
> #undef BPS_TREE_EXTENT_SIZE
>@@ -102,66 +146,119 @@ memtx_tree_data_is_equal(const struct memtx_tree_data *a,
> #undef BPS_TREE_COMPARE_KEY
> #undef BPS_TREE_IS_IDENTICAL
> #undef BPS_TREE_NO_DEBUG
>-#undef bps_tree_elem_t
>-#undef bps_tree_key_t
> #undef bps_tree_arg_t
> 
>+using namespace NS_NO_HINT;
>+using namespace NS_USE_HINT;
>+
>+template <int USE_HINT>
>+struct memtx_tree_selector;
>+
>+template <>
>+struct memtx_tree_selector<0> : NS_NO_HINT::memtx_tree {};
>+
>+template <>
>+struct memtx_tree_selector<1> : NS_USE_HINT::memtx_tree {};
>+
>+template <int USE_HINT>
>+using memtx_tree_t = struct memtx_tree_selector<USE_HINT>;
>+
>+template <int USE_HINT>
>+struct memtx_tree_iterator_selector;
>+
>+template <>
>+struct memtx_tree_iterator_selector<0> {
>+ using type = NS_NO_HINT::memtx_tree_iterator;
>+};
>+
>+template <>
>+struct memtx_tree_iterator_selector<1> {
>+ using type = NS_USE_HINT::memtx_tree_iterator;
>+};
>+
>+template <int USE_HINT>
>+using memtx_tree_iterator_t = typename memtx_tree_iterator_selector<USE_HINT>::type;
>+
>+static void
>+invalidate_tree_iterator(NS_NO_HINT::memtx_tree_iterator *itr)
>+{
>+ *itr = NS_NO_HINT::memtx_tree_invalid_iterator();
>+}
>+
>+static void
>+invalidate_tree_iterator(NS_USE_HINT::memtx_tree_iterator *itr)
>+{
>+ *itr = NS_USE_HINT::memtx_tree_invalid_iterator();
>+}
>+
>+template <int USE_HINT>
> struct memtx_tree_index {
>  struct index base;
>- struct memtx_tree tree;
>- struct memtx_tree_data *build_array;
>+ memtx_tree_t<USE_HINT> tree;
>+ struct memtx_tree_data<USE_HINT> *build_array;
>  size_t build_array_size, build_array_alloc_size;
>  struct memtx_gc_task gc_task;
>- struct memtx_tree_iterator gc_iterator;
>+ memtx_tree_iterator_t<USE_HINT> gc_iterator;
> };
> 
> /* {{{ Utilities. *************************************************/
> 
>+template <class TREE>
> static inline struct key_def *
>-memtx_tree_cmp_def(struct memtx_tree *tree)
>+memtx_tree_cmp_def(TREE *tree)
> {
>  return tree->arg;
> }
> 
>+template <int USE_HINT>
> static int
> memtx_tree_qcompare(const void* a, const void *b, void *c)
> {
>- const struct memtx_tree_data *data_a = (struct memtx_tree_data *)a;
>- const struct memtx_tree_data *data_b = (struct memtx_tree_data *)b;
>+ const struct memtx_tree_data<USE_HINT> *data_a =
>+ (struct memtx_tree_data<USE_HINT> *)a;
>+ const struct memtx_tree_data<USE_HINT> *data_b =
>+ (struct memtx_tree_data<USE_HINT> *)b;
>  struct key_def *key_def = (struct key_def *)c;
>  return tuple_compare(data_a->tuple, data_a->hint, data_b->tuple,
>  data_b->hint, key_def);
> }
> 
> /* {{{ MemtxTree Iterators ****************************************/
>+template <int USE_HINT>
> struct tree_iterator {
>  struct iterator base;
>- struct memtx_tree_iterator tree_iterator;
>+ memtx_tree_iterator_t<USE_HINT> tree_iterator;
>  enum iterator_type type;
>- struct memtx_tree_key_data key_data;
>- struct memtx_tree_data current;
>+ struct memtx_tree_key_data<USE_HINT> key_data;
>+ struct memtx_tree_data<USE_HINT> current;
>  /** Memory pool the iterator was allocated from. */
>  struct mempool *pool;
> };
> 
>-static_assert(sizeof(struct tree_iterator) <= MEMTX_ITERATOR_SIZE,
>- "sizeof(struct tree_iterator) must be less than or equal "
>+static_assert(sizeof(struct tree_iterator<0>) <= MEMTX_ITERATOR_SIZE,
>+ "sizeof(struct tree_iterator<0>) must be less than or equal "
>+ "to MEMTX_ITERATOR_SIZE");
>+static_assert(sizeof(struct tree_iterator<1>) <= MEMTX_ITERATOR_SIZE,
>+ "sizeof(struct tree_iterator<1>) must be less than or equal "
>  "to MEMTX_ITERATOR_SIZE");
> 
>+template <int USE_HINT>
> static void
> tree_iterator_free(struct iterator *iterator);
> 
>-static inline struct tree_iterator *
>-tree_iterator(struct iterator *it)
>+template <int USE_HINT>
>+static inline struct tree_iterator<USE_HINT> *
>+get_tree_iterator(struct iterator *it)
> {
>- assert(it->free == tree_iterator_free);
>- return (struct tree_iterator *) it;
>+ assert(it->free == &tree_iterator_free<USE_HINT>);
>+ return (struct tree_iterator<USE_HINT> *) it;
> }
> 
>+template <int USE_HINT>
> static void
> tree_iterator_free(struct iterator *iterator)
> {
>- struct tree_iterator *it = tree_iterator(iterator);
>+ struct tree_iterator<USE_HINT> *it = get_tree_iterator<USE_HINT>(iterator);
>  struct tuple *tuple = it->current.tuple;
>  if (tuple != NULL)
>  tuple_unref(tuple);
>@@ -176,14 +273,15 @@ tree_iterator_dummie(struct iterator *iterator, struct tuple **ret)
>  return 0;
> }
> 
>+template <int USE_HINT>
> static int
> tree_iterator_next_base(struct iterator *iterator, struct tuple **ret)
> {
>- struct memtx_tree_index *index =
>- (struct memtx_tree_index *)iterator->index;
>- struct tree_iterator *it = tree_iterator(iterator);
>+ struct memtx_tree_index<USE_HINT> *index =
>+ (struct memtx_tree_index<USE_HINT> *)iterator->index;
>+ struct tree_iterator<USE_HINT> *it = get_tree_iterator<USE_HINT>(iterator);
>  assert(it->current.tuple != NULL);
>- struct memtx_tree_data *check =
>+ struct memtx_tree_data<USE_HINT> *check =
>  memtx_tree_iterator_get_elem(&index->tree, &it->tree_iterator);
>  if (check == NULL || !memtx_tree_data_is_equal(check, &it->current)) {
>  it->tree_iterator = memtx_tree_upper_bound_elem(&index->tree,
>@@ -192,7 +290,7 @@ tree_iterator_next_base(struct iterator *iterator, struct tuple **ret)
>  memtx_tree_iterator_next(&index->tree, &it->tree_iterator);
>  }
>  tuple_unref(it->current.tuple);
>- struct memtx_tree_data *res =
>+ struct memtx_tree_data<USE_HINT> *res =
>  memtx_tree_iterator_get_elem(&index->tree, &it->tree_iterator);
>  if (res == NULL) {
>  iterator->next = tree_iterator_dummie;
>@@ -206,14 +304,15 @@ tree_iterator_next_base(struct iterator *iterator, struct tuple **ret)
>  return 0;
> }
> 
>+template <int USE_HINT>
> static int
> tree_iterator_prev_base(struct iterator *iterator, struct tuple **ret)
> {
>- struct memtx_tree_index *index =
>- (struct memtx_tree_index *)iterator->index;
>- struct tree_iterator *it = tree_iterator(iterator);
>+ struct memtx_tree_index<USE_HINT> *index =
>+ (struct memtx_tree_index<USE_HINT> *)iterator->index;
>+ struct tree_iterator<USE_HINT> *it = get_tree_iterator<USE_HINT>(iterator);
>  assert(it->current.tuple != NULL);
>- struct memtx_tree_data *check =
>+ struct memtx_tree_data<USE_HINT> *check =
>  memtx_tree_iterator_get_elem(&index->tree, &it->tree_iterator);
>  if (check == NULL || !memtx_tree_data_is_equal(check, &it->current)) {
>  it->tree_iterator = memtx_tree_lower_bound_elem(&index->tree,
>@@ -221,7 +320,7 @@ tree_iterator_prev_base(struct iterator *iterator, struct tuple **ret)
>  }
>  memtx_tree_iterator_prev(&index->tree, &it->tree_iterator);
>  tuple_unref(it->current.tuple);
>- struct memtx_tree_data *res =
>+ struct memtx_tree_data<USE_HINT> *res =
>  memtx_tree_iterator_get_elem(&index->tree, &it->tree_iterator);
>  if (!res) {
>  iterator->next = tree_iterator_dummie;
>@@ -235,14 +334,15 @@ tree_iterator_prev_base(struct iterator *iterator, struct tuple **ret)
>  return 0;
> }
> 
>+template <int USE_HINT>
> static int
> tree_iterator_next_equal_base(struct iterator *iterator, struct tuple **ret)
> {
>- struct memtx_tree_index *index =
>- (struct memtx_tree_index *)iterator->index;
>- struct tree_iterator *it = tree_iterator(iterator);
>+ struct memtx_tree_index<USE_HINT> *index =
>+ (struct memtx_tree_index<USE_HINT> *)iterator->index;
>+ struct tree_iterator<USE_HINT> *it = get_tree_iterator<USE_HINT>(iterator);
>  assert(it->current.tuple != NULL);
>- struct memtx_tree_data *check =
>+ struct memtx_tree_data<USE_HINT> *check =
>  memtx_tree_iterator_get_elem(&index->tree, &it->tree_iterator);
>  if (check == NULL || !memtx_tree_data_is_equal(check, &it->current)) {
>  it->tree_iterator = memtx_tree_upper_bound_elem(&index->tree,
>@@ -251,7 +351,7 @@ tree_iterator_next_equal_base(struct iterator *iterator, struct tuple **ret)
>  memtx_tree_iterator_next(&index->tree, &it->tree_iterator);
>  }
>  tuple_unref(it->current.tuple);
>- struct memtx_tree_data *res =
>+ struct memtx_tree_data<USE_HINT> *res =
>  memtx_tree_iterator_get_elem(&index->tree, &it->tree_iterator);
>  /* Use user key def to save a few loops. */
>  if (res == NULL ||
>@@ -271,14 +371,15 @@ tree_iterator_next_equal_base(struct iterator *iterator, struct tuple **ret)
>  return 0;
> }
> 
>+template <int USE_HINT>
> static int
> tree_iterator_prev_equal_base(struct iterator *iterator, struct tuple **ret)
> {
>- struct memtx_tree_index *index =
>- (struct memtx_tree_index *)iterator->index;
>- struct tree_iterator *it = tree_iterator(iterator);
>+ struct memtx_tree_index<USE_HINT> *index =
>+ (struct memtx_tree_index<USE_HINT> *)iterator->index;
>+ struct tree_iterator<USE_HINT> *it = get_tree_iterator<USE_HINT>(iterator);
>  assert(it->current.tuple != NULL);
>- struct memtx_tree_data *check =
>+ struct memtx_tree_data<USE_HINT> *check =
>  memtx_tree_iterator_get_elem(&index->tree, &it->tree_iterator);
>  if (check == NULL || !memtx_tree_data_is_equal(check, &it->current)) {
>  it->tree_iterator = memtx_tree_lower_bound_elem(&index->tree,
>@@ -286,7 +387,7 @@ tree_iterator_prev_equal_base(struct iterator *iterator, struct tuple **ret)
>  }
>  memtx_tree_iterator_prev(&index->tree, &it->tree_iterator);
>  tuple_unref(it->current.tuple);
>- struct memtx_tree_data *res =
>+ struct memtx_tree_data<USE_HINT> *res =
>  memtx_tree_iterator_get_elem(&index->tree, &it->tree_iterator);
>  /* Use user key def to save a few loops. */
>  if (res == NULL ||
>@@ -307,28 +408,30 @@ tree_iterator_prev_equal_base(struct iterator *iterator, struct tuple **ret)
> }
> 
> #define WRAP_ITERATOR_METHOD(name) \
>+template <int USE_HINT> \
> static int \
> name(struct iterator *iterator, struct tuple **ret) \
> { \
>- struct memtx_tree *tree = \
>- &((struct memtx_tree_index *)iterator->index)->tree; \
>- struct tree_iterator *it = tree_iterator(iterator); \
>- struct memtx_tree_iterator *ti = &it->tree_iterator; \
>+ memtx_tree_t<USE_HINT> *tree = \
>+ &((struct memtx_tree_index<USE_HINT> *)iterator->index)->tree; \
>+ struct tree_iterator<USE_HINT> *it = \
>+ get_tree_iterator<USE_HINT>(iterator); \
>+ memtx_tree_iterator_t<USE_HINT> *ti = &it->tree_iterator; \
>  uint32_t iid = iterator->index->def->iid; \
>  bool is_multikey = iterator->index->def->key_def->is_multikey; \
>  struct txn *txn = in_txn(); \
>  struct space *space = space_by_id(iterator->space_id); \
>  bool is_rw = txn != NULL; \
>  do { \
>- int rc = name##_base(iterator, ret); \
>+ int rc = name##_base<USE_HINT>(iterator, ret); \
>  if (rc != 0 || *ret == NULL) \
>  return rc; \
>  uint32_t mk_index = 0; \
>  if (is_multikey) { \
>- struct memtx_tree_data *check = \
>+ struct memtx_tree_data<USE_HINT> *check = \
>  memtx_tree_iterator_get_elem(tree, ti); \
>  assert(check != NULL); \
>- mk_index = check->hint; \
>+ mk_index = (uint32_t)check->hint; \
>  } \
>  *ret = memtx_tx_tuple_clarify(txn, space, *ret, \
>  iid, mk_index, is_rw); \
>@@ -347,27 +450,28 @@ WRAP_ITERATOR_METHOD(tree_iterator_prev_equal);
> 
> #undef WRAP_ITERATOR_METHOD
> 
>+template <int USE_HINT>
> static void
>-tree_iterator_set_next_method(struct tree_iterator *it)
>+tree_iterator_set_next_method(struct tree_iterator<USE_HINT> *it)
> {
>  assert(it->current.tuple != NULL);
>  switch (it->type) {
>  case ITER_EQ:
>- it->base.next = tree_iterator_next_equal;
>+ it->base.next = tree_iterator_next_equal<USE_HINT>;
>  break;
>  case ITER_REQ:
>- it->base.next = tree_iterator_prev_equal;
>+ it->base.next = tree_iterator_prev_equal<USE_HINT>;
>  break;
>  case ITER_ALL:
>- it->base.next = tree_iterator_next;
>+ it->base.next = tree_iterator_next<USE_HINT>;
>  break;
>  case ITER_LT:
>  case ITER_LE:
>- it->base.next = tree_iterator_prev;
>+ it->base.next = tree_iterator_prev<USE_HINT>;
>  break;
>  case ITER_GE:
>  case ITER_GT:
>- it->base.next = tree_iterator_next;
>+ it->base.next = tree_iterator_next<USE_HINT>;
>  break;
>  default:
>  /* The type was checked in initIterator */
>@@ -375,15 +479,16 @@ tree_iterator_set_next_method(struct tree_iterator *it)
>  }
> }
> 
>+template <int USE_HINT>
> static int
> tree_iterator_start(struct iterator *iterator, struct tuple **ret)
> {
>  *ret = NULL;
>- struct memtx_tree_index *index =
>- (struct memtx_tree_index *)iterator->index;
>- struct tree_iterator *it = tree_iterator(iterator);
>+ struct memtx_tree_index<USE_HINT> *index =
>+ (struct memtx_tree_index<USE_HINT> *)iterator->index;
>+ struct tree_iterator<USE_HINT> *it = get_tree_iterator<USE_HINT>(iterator);
>  it->base.next = tree_iterator_dummie;
>- struct memtx_tree *tree = &index->tree;
>+ memtx_tree_t<USE_HINT> *tree = &index->tree;
>  enum iterator_type type = it->type;
>  bool exact = false;
>  assert(it->current.tuple == NULL);
>@@ -423,8 +528,8 @@ tree_iterator_start(struct iterator *iterator, struct tuple **ret)
>  }
>  }
> 
>- struct memtx_tree_data *res = memtx_tree_iterator_get_elem(tree,
>- &it->tree_iterator);
>+ struct memtx_tree_data<USE_HINT> *res =
>+ memtx_tree_iterator_get_elem(tree, &it->tree_iterator);
>  if (!res)
>  return 0;
>  *ret = res->tuple;
>@@ -454,14 +559,16 @@ tree_iterator_start(struct iterator *iterator, struct tuple **ret)
> 
> /* {{{ MemtxTree **********************************************************/
> 
>+template <int USE_HINT>
> static void
>-memtx_tree_index_free(struct memtx_tree_index *index)
>+memtx_tree_index_free(struct memtx_tree_index<USE_HINT> *index)
> {
>  memtx_tree_destroy(&index->tree);
>  free(index->build_array);
>  free(index);
> }
> 
>+template <int USE_HINT>
> static void
> memtx_tree_index_gc_run(struct memtx_gc_task *task, bool *done)
> {
>@@ -475,14 +582,14 @@ memtx_tree_index_gc_run(struct memtx_gc_task *task, bool *done)
>  enum { YIELD_LOOPS = 10 };
> #endif
> 
>- struct memtx_tree_index *index = container_of(task,
>- struct memtx_tree_index, gc_task);
>- struct memtx_tree *tree = &index->tree;
>- struct memtx_tree_iterator *itr = &index->gc_iterator;
>+ struct memtx_tree_index<USE_HINT> *index = container_of(task,
>+ struct memtx_tree_index<USE_HINT>, gc_task);
>+ memtx_tree_t<USE_HINT> *tree = &index->tree;
>+ memtx_tree_iterator_t<USE_HINT> *itr = &index->gc_iterator;
> 
>  unsigned int loops = 0;
>  while (!memtx_tree_iterator_is_invalid(itr)) {
>- struct memtx_tree_data *res =
>+ struct memtx_tree_data<USE_HINT> *res =
>  memtx_tree_iterator_get_elem(tree, itr);
>  memtx_tree_iterator_next(tree, itr);
>  tuple_unref(res->tuple);
>@@ -494,23 +601,32 @@ memtx_tree_index_gc_run(struct memtx_gc_task *task, bool *done)
>  *done = true;
> }
> 
>+template <int USE_HINT>
> static void
> memtx_tree_index_gc_free(struct memtx_gc_task *task)
> {
>- struct memtx_tree_index *index = container_of(task,
>- struct memtx_tree_index, gc_task);
>+ struct memtx_tree_index<USE_HINT> *index = container_of(task,
>+ struct memtx_tree_index<USE_HINT>, gc_task);
>  memtx_tree_index_free(index);
> }
> 
>-static const struct memtx_gc_task_vtab memtx_tree_index_gc_vtab = {
>- .run = memtx_tree_index_gc_run,
>- .free = memtx_tree_index_gc_free,
>+template <int USE_HINT>
>+static struct memtx_gc_task_vtab * get_memtx_tree_index_gc_vtab()
>+{
>+ static memtx_gc_task_vtab tab =
>+ {
>+ .run = memtx_tree_index_gc_run<USE_HINT>,
>+ .free = memtx_tree_index_gc_free<USE_HINT>,
>+ };
>+ return &tab;
> };
> 
>+template <int USE_HINT>
> static void
> memtx_tree_index_destroy(struct index *base)
> {
>- struct memtx_tree_index *index = (struct memtx_tree_index *)base;
>+ struct memtx_tree_index<USE_HINT> *index =
>+ (struct memtx_tree_index<USE_HINT> *)base;
>  struct memtx_engine *memtx = (struct memtx_engine *)base->engine;
>  if (base->def->iid == 0) {
>  /*
>@@ -518,7 +634,7 @@ memtx_tree_index_destroy(struct index *base)
>  * in the index, which may take a while. Schedule a
>  * background task in order not to block tx thread.
>  */
>- index->gc_task.vtab = &memtx_tree_index_gc_vtab;
>+ index->gc_task.vtab = get_memtx_tree_index_gc_vtab<USE_HINT>();
>  index->gc_iterator = memtx_tree_iterator_first(&index->tree);
>  memtx_engine_schedule_gc(memtx, &index->gc_task);
>  } else {
>@@ -530,10 +646,12 @@ memtx_tree_index_destroy(struct index *base)
>  }
> }
> 
>+template <int USE_HINT>
> static void
> memtx_tree_index_update_def(struct index *base)
> {
>- struct memtx_tree_index *index = (struct memtx_tree_index *)base;
>+ struct memtx_tree_index<USE_HINT> *index =
>+ (struct memtx_tree_index<USE_HINT> *)base;
>  struct index_def *def = base->def;
>  /*
>  * We use extended key def for non-unique and nullable
>@@ -553,51 +671,62 @@ memtx_tree_index_depends_on_pk(struct index *base)
>  return !def->opts.is_unique || def->key_def->is_nullable;
> }
> 
>+template <int USE_HINT>
> static ssize_t
> memtx_tree_index_size(struct index *base)
> {
>- struct memtx_tree_index *index = (struct memtx_tree_index *)base;
>+ struct memtx_tree_index<USE_HINT> *index =
>+ (struct memtx_tree_index<USE_HINT> *)base;
>  return memtx_tree_size(&index->tree);
> }
> 
>+template <int USE_HINT>
> static ssize_t
> memtx_tree_index_bsize(struct index *base)
> {
>- struct memtx_tree_index *index = (struct memtx_tree_index *)base;
>+ struct memtx_tree_index<USE_HINT> *index =
>+ (struct memtx_tree_index<USE_HINT> *)base;
>  return memtx_tree_mem_used(&index->tree);
> }
> 
>+template <int USE_HINT>
> 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 memtx_tree_data *res = memtx_tree_random(&index->tree, rnd);
>+ struct memtx_tree_index<USE_HINT> *index =
>+ (struct memtx_tree_index<USE_HINT> *)base;
>+ struct memtx_tree_data<USE_HINT> *res = memtx_tree_random(&index->tree, rnd);
>  *result = res != NULL ? res->tuple : NULL;
>  return 0;
> }
> 
>+template <int USE_HINT>
> static ssize_t
> memtx_tree_index_count(struct index *base, enum iterator_type type,
>  const char *key, uint32_t part_count)
> {
>  if (type == ITER_ALL)
>- return memtx_tree_index_size(base); /* optimization */
>+ return memtx_tree_index_size<USE_HINT>(base); /* optimization */
>  return generic_index_count(base, type, key, part_count);
> }
> 
>+template <int USE_HINT>
> static int
> memtx_tree_index_get(struct index *base, const char *key,
>  uint32_t part_count, struct tuple **result)
> {
>  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_index<USE_HINT> *index =
>+ (struct memtx_tree_index<USE_HINT> *)base;
>  struct key_def *cmp_def = memtx_tree_cmp_def(&index->tree);
>- struct memtx_tree_key_data key_data;
>+ struct memtx_tree_key_data<USE_HINT> key_data;
>  key_data.key = key;
>  key_data.part_count = part_count;
>- key_data.hint = key_hint(key, part_count, cmp_def);
>- struct memtx_tree_data *res = memtx_tree_find(&index->tree, &key_data);
>+ if (USE_HINT)
>+ key_data.set_hint(key_hint(key, part_count, cmp_def));
>+ struct memtx_tree_data<USE_HINT> *res =
>+ memtx_tree_find(&index->tree, &key_data);
>  if (res == NULL) {
>  *result = NULL;
>  return 0;
>@@ -611,18 +740,21 @@ memtx_tree_index_get(struct index *base, const char *key,
>  return 0;
> }
> 
>+template <int USE_HINT>
> 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;
>+ struct memtx_tree_index<USE_HINT> *index =
>+ (struct memtx_tree_index<USE_HINT> *)base;
>  struct key_def *cmp_def = memtx_tree_cmp_def(&index->tree);
>  if (new_tuple) {
>- struct memtx_tree_data new_data;
>+ struct memtx_tree_data<USE_HINT> new_data;
>  new_data.tuple = new_tuple;
>- new_data.hint = tuple_hint(new_tuple, cmp_def);
>- struct memtx_tree_data dup_data;
>+ if (USE_HINT)
>+ new_data.set_hint(tuple_hint(new_tuple, cmp_def));
>+ struct memtx_tree_data<USE_HINT> dup_data;
>  dup_data.tuple = NULL;
> 
>  /* Try to optimistically replace the new_tuple. */
>@@ -652,9 +784,10 @@ memtx_tree_index_replace(struct index *base, struct tuple *old_tuple,
>  }
>  }
>  if (old_tuple) {
>- struct memtx_tree_data old_data;
>+ struct memtx_tree_data<USE_HINT> old_data;
>  old_data.tuple = old_tuple;
>- old_data.hint = tuple_hint(old_tuple, cmp_def);
>+ if (USE_HINT)
>+ old_data.set_hint(tuple_hint(old_tuple, cmp_def));
>  memtx_tree_delete(&index->tree, old_data);
>  }
>  *result = old_tuple;
>@@ -667,13 +800,13 @@ memtx_tree_index_replace(struct index *base, struct tuple *old_tuple,
>  * by all it's multikey indexes.
>  */
> static int
>-memtx_tree_index_replace_multikey_one(struct memtx_tree_index *index,
>+memtx_tree_index_replace_multikey_one(struct memtx_tree_index<1> *index,
>  struct tuple *old_tuple, struct tuple *new_tuple,
>  enum dup_replace_mode mode, hint_t hint,
>- struct memtx_tree_data *replaced_data,
>+ struct memtx_tree_data<1> *replaced_data,
>  bool *is_multikey_conflict)
> {
>- struct memtx_tree_data new_data, dup_data;
>+ struct memtx_tree_data<1> new_data, dup_data;
>  new_data.tuple = new_tuple;
>  new_data.hint = hint;
>  dup_data.tuple = NULL;
>@@ -720,11 +853,11 @@ memtx_tree_index_replace_multikey_one(struct memtx_tree_index *index,
>  * delete operation is fault-tolerant.
>  */
> static void
>-memtx_tree_index_replace_multikey_rollback(struct memtx_tree_index *index,
>+memtx_tree_index_replace_multikey_rollback(struct memtx_tree_index<1> *index,
>  struct tuple *new_tuple, struct tuple *replaced_tuple,
>  int err_multikey_idx)
> {
>- struct memtx_tree_data data;
>+ struct memtx_tree_data<1> data;
>  if (replaced_tuple != NULL) {
>  /* Restore replaced tuple index occurrences. */
>  struct key_def *cmp_def = memtx_tree_cmp_def(&index->tree);
>@@ -798,7 +931,7 @@ memtx_tree_index_replace_multikey(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;
>+ struct memtx_tree_index<1> *index = (struct memtx_tree_index<1> *)base;
>  struct key_def *cmp_def = memtx_tree_cmp_def(&index->tree);
>  *result = NULL;
>  if (new_tuple != NULL) {
>@@ -808,7 +941,7 @@ memtx_tree_index_replace_multikey(struct index *base, struct tuple *old_tuple,
>  for (; (uint32_t) multikey_idx < multikey_count;
>  multikey_idx++) {
>  bool is_multikey_conflict;
>- struct memtx_tree_data replaced_data;
>+ struct memtx_tree_data<1> replaced_data;
>  err = memtx_tree_index_replace_multikey_one(index,
>  old_tuple, new_tuple, mode,
>  multikey_idx, &replaced_data,
>@@ -833,7 +966,7 @@ memtx_tree_index_replace_multikey(struct index *base, struct tuple *old_tuple,
>  }
>  }
>  if (old_tuple != NULL) {
>- struct memtx_tree_data data;
>+ struct memtx_tree_data<1> data;
>  data.tuple = old_tuple;
>  uint32_t multikey_count =
>  tuple_multikey_count(old_tuple, cmp_def);
>@@ -865,7 +998,7 @@ struct func_key_undo {
>  /** A link to organize entries in list. */
>  struct rlist link;
>  /** An inserted record copy. */
>- struct memtx_tree_data key;
>+ struct memtx_tree_data<1> key;
> };
> 
> /** Allocate a new func_key_undo on given region. */
>@@ -888,7 +1021,7 @@ func_key_undo_new(struct region *region)
>  * return a given index object in it's original state.
>  */
> static void
>-memtx_tree_func_index_replace_rollback(struct memtx_tree_index *index,
>+memtx_tree_func_index_replace_rollback(struct memtx_tree_index<1> *index,
>  struct rlist *old_keys,
>  struct rlist *new_keys)
> {
>@@ -919,7 +1052,7 @@ memtx_tree_func_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;
>+ struct memtx_tree_index<1> *index = (struct memtx_tree_index<1> *)base;
>  struct index_def *index_def = index->base.def;
>  assert(index_def->key_def->for_func_index);
> 
>@@ -952,7 +1085,7 @@ memtx_tree_func_index_replace(struct index *base, struct tuple *old_tuple,
>  undo->key.hint = (hint_t)key;
>  rlist_add(&new_keys, &undo->link);
>  bool is_multikey_conflict;
>- struct memtx_tree_data old_data;
>+ struct memtx_tree_data<1> old_data;
>  old_data.tuple = NULL;
>  err = memtx_tree_index_replace_multikey_one(index,
>  old_tuple, new_tuple,
>@@ -1015,7 +1148,7 @@ memtx_tree_func_index_replace(struct index *base, struct tuple *old_tuple,
>  if (key_list_iterator_create(&it, old_tuple, index_def, false,
>  func_index_key_dummy_alloc) != 0)
>  goto end;
>- struct memtx_tree_data data, deleted_data;
>+ struct memtx_tree_data<1> data, deleted_data;
>  data.tuple = old_tuple;
>  const char *key;
>  while (key_list_iterator_next(&it, &key) == 0 && key != NULL) {
>@@ -1040,11 +1173,13 @@ end:
>  return rc;
> }
> 
>+template <int USE_HINT>
> static struct iterator *
> memtx_tree_index_create_iterator(struct index *base, enum iterator_type type,
>  const char *key, uint32_t part_count)
> {
>- struct memtx_tree_index *index = (struct memtx_tree_index *)base;
>+ struct memtx_tree_index<USE_HINT> *index =
>+ (struct memtx_tree_index<USE_HINT> *)base;
>  struct memtx_engine *memtx = (struct memtx_engine *)base->engine;
>  struct key_def *cmp_def = memtx_tree_cmp_def(&index->tree);
> 
>@@ -1064,42 +1199,47 @@ memtx_tree_index_create_iterator(struct index *base, enum iterator_type type,
>  key = NULL;
>  }
> 
>- struct tree_iterator *it = (struct tree_iterator *)
>+ struct tree_iterator<USE_HINT> *it = (struct tree_iterator<USE_HINT> *)
>  mempool_alloc(&memtx->iterator_pool);
>  if (it == NULL) {
>- diag_set(OutOfMemory, sizeof(struct tree_iterator),
>+ diag_set(OutOfMemory, sizeof(struct tree_iterator<USE_HINT>),
>  "memtx_tree_index", "iterator");
>  return NULL;
>  }
>  iterator_create(&it->base, base);
>  it->pool = &memtx->iterator_pool;
>- it->base.next = tree_iterator_start;
>- it->base.free = tree_iterator_free;
>+ it->base.next = tree_iterator_start<USE_HINT>;
>+ it->base.free = tree_iterator_free<USE_HINT>;
>  it->type = type;
>  it->key_data.key = key;
>  it->key_data.part_count = part_count;
>- it->key_data.hint = key_hint(key, part_count, cmp_def);
>- it->tree_iterator = memtx_tree_invalid_iterator();
>+ if (USE_HINT)
>+ it->key_data.set_hint(key_hint(key, part_count, cmp_def));
>+ invalidate_tree_iterator(&it->tree_iterator);
>  it->current.tuple = NULL;
>  return (struct iterator *)it;
> }
> 
>+template <int USE_HINT>
> static void
> memtx_tree_index_begin_build(struct index *base)
> {
>- struct memtx_tree_index *index = (struct memtx_tree_index *)base;
>+ struct memtx_tree_index<USE_HINT> *index =
>+ (struct memtx_tree_index<USE_HINT> *)base;
>  assert(memtx_tree_size(&index->tree) == 0);
>  (void)index;
> }
> 
>+template <int USE_HINT>
> static int
> memtx_tree_index_reserve(struct index *base, uint32_t size_hint)
> {
>- struct memtx_tree_index *index = (struct memtx_tree_index *)base;
>+ struct memtx_tree_index<USE_HINT> *index =
>+ (struct memtx_tree_index<USE_HINT> *)base;
>  if (size_hint < index->build_array_alloc_size)
>  return 0;
>- struct memtx_tree_data *tmp =
>- (struct memtx_tree_data *)
>+ struct memtx_tree_data<USE_HINT> *tmp =
>+ (struct memtx_tree_data<USE_HINT> *)
>  realloc(index->build_array, size_hint * sizeof(*tmp));
>  if (tmp == NULL) {
>  diag_set(OutOfMemory, size_hint * sizeof(*tmp),
>@@ -1111,14 +1251,15 @@ memtx_tree_index_reserve(struct index *base, uint32_t size_hint)
>  return 0;
> }
> 
>+template <int USE_HINT>
> /** Initialize the next element of the index build_array. */
> static int
>-memtx_tree_index_build_array_append(struct memtx_tree_index *index,
>+memtx_tree_index_build_array_append(struct memtx_tree_index<USE_HINT> *index,
>  struct tuple *tuple, hint_t hint)
> {
>  if (index->build_array == NULL) {
>  index->build_array =
>- (struct memtx_tree_data *)malloc(MEMTX_EXTENT_SIZE);
>+ (struct memtx_tree_data<USE_HINT> *)malloc(MEMTX_EXTENT_SIZE);
>  if (index->build_array == NULL) {
>  diag_set(OutOfMemory, MEMTX_EXTENT_SIZE,
>  "memtx_tree_index", "build_next");
>@@ -1131,8 +1272,8 @@ memtx_tree_index_build_array_append(struct memtx_tree_index *index,
>  if (index->build_array_size == index->build_array_alloc_size) {
>  index->build_array_alloc_size = index->build_array_alloc_size +
>  DIV_ROUND_UP(index->build_array_alloc_size, 2);
>- struct memtx_tree_data *tmp =
>- (struct memtx_tree_data *)realloc(index->build_array,
>+ struct memtx_tree_data<USE_HINT> *tmp =
>+ (struct memtx_tree_data<USE_HINT> *)realloc(index->build_array,
>  index->build_array_alloc_size * sizeof(*tmp));
>  if (tmp == NULL) {
>  diag_set(OutOfMemory, index->build_array_alloc_size *
>@@ -1141,17 +1282,20 @@ memtx_tree_index_build_array_append(struct memtx_tree_index *index,
>  }
>  index->build_array = tmp;
>  }
>- struct memtx_tree_data *elem =
>+ struct memtx_tree_data<USE_HINT> *elem =
>  &index->build_array[index->build_array_size++];
>  elem->tuple = tuple;
>- elem->hint = hint;
>+ if (USE_HINT)
>+ elem->set_hint(hint);
>  return 0;
> }
> 
>+template <int USE_HINT>
> static int
> memtx_tree_index_build_next(struct index *base, struct tuple *tuple)
> {
>- struct memtx_tree_index *index = (struct memtx_tree_index *)base;
>+ struct memtx_tree_index<USE_HINT> *index =
>+ (struct memtx_tree_index<USE_HINT> *)base;
>  struct key_def *cmp_def = memtx_tree_cmp_def(&index->tree);
>  return memtx_tree_index_build_array_append(index, tuple,
>  tuple_hint(tuple, cmp_def));
>@@ -1160,7 +1304,7 @@ memtx_tree_index_build_next(struct index *base, struct tuple *tuple)
> static int
> memtx_tree_index_build_next_multikey(struct index *base, struct tuple *tuple)
> {
>- struct memtx_tree_index *index = (struct memtx_tree_index *)base;
>+ struct memtx_tree_index<1> *index = (struct memtx_tree_index<1> *)base;
>  struct key_def *cmp_def = memtx_tree_cmp_def(&index->tree);
>  uint32_t multikey_count = tuple_multikey_count(tuple, cmp_def);
>  for (uint32_t multikey_idx = 0; multikey_idx < multikey_count;
>@@ -1175,7 +1319,7 @@ memtx_tree_index_build_next_multikey(struct index *base, struct tuple *tuple)
> static int
> memtx_tree_func_index_build_next(struct index *base, struct tuple *tuple)
> {
>- struct memtx_tree_index *index = (struct memtx_tree_index *)base;
>+ struct memtx_tree_index<1> *index = (struct memtx_tree_index<1> *)base;
>  struct index_def *index_def = index->base.def;
>  assert(index_def->key_def->for_func_index);
> 
>@@ -1211,8 +1355,9 @@ error:
>  * of equal tuples (in terms of index's cmp_def and have same
>  * tuple pointer). The build_array is expected to be sorted.
>  */
>+template <int USE_HINT>
> static void
>-memtx_tree_index_build_array_deduplicate(struct memtx_tree_index *index,
>+memtx_tree_index_build_array_deduplicate(struct memtx_tree_index<USE_HINT> *index,
>  void (*destroy)(struct tuple *tuple, const char *hint))
> {
>  if (index->build_array_size == 0)
>@@ -1246,13 +1391,16 @@ memtx_tree_index_build_array_deduplicate(struct memtx_tree_index *index,
>  index->build_array_size = w_idx + 1;
> }
> 
>+template <int USE_HINT>
> static void
> memtx_tree_index_end_build(struct index *base)
> {
>- struct memtx_tree_index *index = (struct memtx_tree_index *)base;
>+ struct memtx_tree_index<USE_HINT> *index =
>+ (struct memtx_tree_index<USE_HINT> *)base;
>  struct key_def *cmp_def = memtx_tree_cmp_def(&index->tree);
>  qsort_arg(index->build_array, index->build_array_size,
>- sizeof(index->build_array[0]), memtx_tree_qcompare, cmp_def);
>+ sizeof(index->build_array[0]),
>+ memtx_tree_qcompare<USE_HINT>, cmp_def);
>  if (cmp_def->is_multikey) {
>  /*
>  * Multikey index may have equal(in terms of
>@@ -1261,9 +1409,9 @@ memtx_tree_index_end_build(struct index *base)
>  * the following memtx_tree_build assumes that
>  * all keys are unique.
>  */
>- memtx_tree_index_build_array_deduplicate(index, NULL);
>+ memtx_tree_index_build_array_deduplicate<USE_HINT>(index, NULL);
>  } else if (cmp_def->for_func_index) {
>- memtx_tree_index_build_array_deduplicate(index,
>+ memtx_tree_index_build_array_deduplicate<USE_HINT>(index,
>  tuple_chunk_delete);
>  }
>  memtx_tree_build(&index->tree, index->build_array,
>@@ -1275,19 +1423,21 @@ memtx_tree_index_end_build(struct index *base)
>  index->build_array_alloc_size = 0;
> }
> 
>+template <int USE_HINT>
> struct tree_snapshot_iterator {
>  struct snapshot_iterator base;
>- struct memtx_tree_index *index;
>- struct memtx_tree_iterator tree_iterator;
>+ struct memtx_tree_index<USE_HINT> *index;
>+ memtx_tree_iterator_t<USE_HINT> tree_iterator;
>  struct memtx_tx_snapshot_cleaner cleaner;
> };
> 
>+template <int USE_HINT>
> static void
> tree_snapshot_iterator_free(struct snapshot_iterator *iterator)
> {
>- assert(iterator->free == tree_snapshot_iterator_free);
>- struct tree_snapshot_iterator *it =
>- (struct tree_snapshot_iterator *)iterator;
>+ assert(iterator->free == &tree_snapshot_iterator_free<USE_HINT>);
>+ struct tree_snapshot_iterator<USE_HINT> *it =
>+ (struct tree_snapshot_iterator<USE_HINT> *)iterator;
>  memtx_leave_delayed_free_mode((struct memtx_engine *)
>  it->index->base.engine);
>  memtx_tree_iterator_destroy(&it->index->tree, &it->tree_iterator);
>@@ -1296,17 +1446,18 @@ tree_snapshot_iterator_free(struct snapshot_iterator *iterator)
>  free(iterator);
> }
> 
>+template <int USE_HINT>
> static int
> tree_snapshot_iterator_next(struct snapshot_iterator *iterator,
>  const char **data, uint32_t *size)
> {
>- assert(iterator->free == tree_snapshot_iterator_free);
>- struct tree_snapshot_iterator *it =
>- (struct tree_snapshot_iterator *)iterator;
>- struct memtx_tree *tree = &it->index->tree;
>+ assert(iterator->free == &tree_snapshot_iterator_free<USE_HINT>);
>+ struct tree_snapshot_iterator<USE_HINT> *it =
>+ (struct tree_snapshot_iterator<USE_HINT> *)iterator;
>+ memtx_tree_t<USE_HINT> *tree = &it->index->tree;
> 
>  while (true) {
>- struct memtx_tree_data *res =
>+ struct memtx_tree_data<USE_HINT> *res =
>  memtx_tree_iterator_get_elem(tree, &it->tree_iterator);
> 
>  if (res == NULL) {
>@@ -1333,14 +1484,18 @@ tree_snapshot_iterator_next(struct snapshot_iterator *iterator,
>  * index modifications will not affect the iteration results.
>  * Must be destroyed by iterator->free after usage.
>  */
>+template <int USE_HINT>
> static struct snapshot_iterator *
> memtx_tree_index_create_snapshot_iterator(struct index *base)
> {
>- struct memtx_tree_index *index = (struct memtx_tree_index *)base;
>- struct tree_snapshot_iterator *it =
>- (struct tree_snapshot_iterator *) calloc(1, sizeof(*it));
>+ struct memtx_tree_index<USE_HINT> *index =
>+ (struct memtx_tree_index<USE_HINT> *)base;
>+ struct tree_snapshot_iterator<USE_HINT> *it =
>+ (struct tree_snapshot_iterator<USE_HINT> *)
>+ calloc(1, sizeof(*it));
>  if (it == NULL) {
>- diag_set(OutOfMemory, sizeof(struct tree_snapshot_iterator),
>+ diag_set(OutOfMemory,
>+ sizeof(struct tree_snapshot_iterator<USE_HINT>),
>  "memtx_tree_index", "create_snapshot_iterator");
>  return NULL;
>  }
>@@ -1352,8 +1507,8 @@ memtx_tree_index_create_snapshot_iterator(struct index *base)
>  return NULL;
>  }
> 
>- it->base.free = tree_snapshot_iterator_free;
>- it->base.next = tree_snapshot_iterator_next;
>+ it->base.free = tree_snapshot_iterator_free<USE_HINT>;
>+ it->base.next = tree_snapshot_iterator_next<USE_HINT>;
>  it->index = index;
>  index_ref(base);
>  it->tree_iterator = memtx_tree_iterator_first(&index->tree);
>@@ -1362,94 +1517,124 @@ memtx_tree_index_create_snapshot_iterator(struct index *base)
>  return (struct snapshot_iterator *) it;
> }
> 
>-static const struct index_vtab memtx_tree_index_vtab = {
>- /* .destroy = */ memtx_tree_index_destroy,
>+static const struct index_vtab memtx_tree_no_hint_index_vtab = {
>+ /* .destroy = */ memtx_tree_index_destroy<0>,
>  /* .commit_create = */ generic_index_commit_create,
>  /* .abort_create = */ generic_index_abort_create,
>  /* .commit_modify = */ generic_index_commit_modify,
>  /* .commit_drop = */ generic_index_commit_drop,
>- /* .update_def = */ memtx_tree_index_update_def,
>+ /* .update_def = */ memtx_tree_index_update_def<0>,
>  /* .depends_on_pk = */ memtx_tree_index_depends_on_pk,
>  /* .def_change_requires_rebuild = */
>  memtx_index_def_change_requires_rebuild,
>- /* .size = */ memtx_tree_index_size,
>- /* .bsize = */ memtx_tree_index_bsize,
>+ /* .size = */ memtx_tree_index_size<0>,
>+ /* .bsize = */ memtx_tree_index_bsize<0>,
>  /* .min = */ generic_index_min,
>  /* .max = */ generic_index_max,
>- /* .random = */ memtx_tree_index_random,
>- /* .count = */ memtx_tree_index_count,
>- /* .get = */ memtx_tree_index_get,
>- /* .replace = */ memtx_tree_index_replace,
>- /* .create_iterator = */ memtx_tree_index_create_iterator,
>+ /* .random = */ memtx_tree_index_random<0>,
>+ /* .count = */ memtx_tree_index_count<0>,
>+ /* .get = */ memtx_tree_index_get<0>,
>+ /* .replace = */ memtx_tree_index_replace<0>,
>+ /* .create_iterator = */ memtx_tree_index_create_iterator<0>,
>  /* .create_snapshot_iterator = */
>- memtx_tree_index_create_snapshot_iterator,
>+ memtx_tree_index_create_snapshot_iterator<0>,
>  /* .stat = */ generic_index_stat,
>  /* .compact = */ generic_index_compact,
>  /* .reset_stat = */ generic_index_reset_stat,
>- /* .begin_build = */ memtx_tree_index_begin_build,
>- /* .reserve = */ memtx_tree_index_reserve,
>- /* .build_next = */ memtx_tree_index_build_next,
>- /* .end_build = */ memtx_tree_index_end_build,
>+ /* .begin_build = */ memtx_tree_index_begin_build<0>,
>+ /* .reserve = */ memtx_tree_index_reserve<0>,
>+ /* .build_next = */ memtx_tree_index_build_next<0>,
>+ /* .end_build = */ memtx_tree_index_end_build<0>,
>+};
>+
>+static const struct index_vtab memtx_tree_use_hint_index_vtab = {
>+ /* .destroy = */ memtx_tree_index_destroy<1>,
>+ /* .commit_create = */ generic_index_commit_create,
>+ /* .abort_create = */ generic_index_abort_create,
>+ /* .commit_modify = */ generic_index_commit_modify,
>+ /* .commit_drop = */ generic_index_commit_drop,
>+ /* .update_def = */ memtx_tree_index_update_def<1>,
>+ /* .depends_on_pk = */ memtx_tree_index_depends_on_pk,
>+ /* .def_change_requires_rebuild = */
>+ memtx_index_def_change_requires_rebuild,
>+ /* .size = */ memtx_tree_index_size<1>,
>+ /* .bsize = */ memtx_tree_index_bsize<1>,
>+ /* .min = */ generic_index_min,
>+ /* .max = */ generic_index_max,
>+ /* .random = */ memtx_tree_index_random<1>,
>+ /* .count = */ memtx_tree_index_count<1>,
>+ /* .get = */ memtx_tree_index_get<1>,
>+ /* .replace = */ memtx_tree_index_replace<1>,
>+ /* .create_iterator = */ memtx_tree_index_create_iterator<1>,
>+ /* .create_snapshot_iterator = */
>+ memtx_tree_index_create_snapshot_iterator<1>,
>+ /* .stat = */ generic_index_stat,
>+ /* .compact = */ generic_index_compact,
>+ /* .reset_stat = */ generic_index_reset_stat,
>+ /* .begin_build = */ memtx_tree_index_begin_build<1>,
>+ /* .reserve = */ memtx_tree_index_reserve<1>,
>+ /* .build_next = */ memtx_tree_index_build_next<1>,
>+ /* .end_build = */ memtx_tree_index_end_build<1>,
> };
> 
> static const struct index_vtab memtx_tree_index_multikey_vtab = {
>- /* .destroy = */ memtx_tree_index_destroy,
>+ /* .destroy = */ memtx_tree_index_destroy<1>,
>  /* .commit_create = */ generic_index_commit_create,
>  /* .abort_create = */ generic_index_abort_create,
>  /* .commit_modify = */ generic_index_commit_modify,
>  /* .commit_drop = */ generic_index_commit_drop,
>- /* .update_def = */ memtx_tree_index_update_def,
>+ /* .update_def = */ memtx_tree_index_update_def<1>,
>  /* .depends_on_pk = */ memtx_tree_index_depends_on_pk,
>  /* .def_change_requires_rebuild = */
>  memtx_index_def_change_requires_rebuild,
>- /* .size = */ memtx_tree_index_size,
>- /* .bsize = */ memtx_tree_index_bsize,
>+ /* .size = */ memtx_tree_index_size<1>,
>+ /* .bsize = */ memtx_tree_index_bsize<1>,
>  /* .min = */ generic_index_min,
>  /* .max = */ generic_index_max,
>- /* .random = */ memtx_tree_index_random,
>- /* .count = */ memtx_tree_index_count,
>- /* .get = */ memtx_tree_index_get,
>+ /* .random = */ memtx_tree_index_random<1>,
>+ /* .count = */ memtx_tree_index_count<1>,
>+ /* .get = */ memtx_tree_index_get<1>,
>  /* .replace = */ memtx_tree_index_replace_multikey,
>- /* .create_iterator = */ memtx_tree_index_create_iterator,
>+ /* .create_iterator = */ memtx_tree_index_create_iterator<1>,
>  /* .create_snapshot_iterator = */
>- memtx_tree_index_create_snapshot_iterator,
>+ memtx_tree_index_create_snapshot_iterator<1>,
>  /* .stat = */ generic_index_stat,
>  /* .compact = */ generic_index_compact,
>  /* .reset_stat = */ generic_index_reset_stat,
>- /* .begin_build = */ memtx_tree_index_begin_build,
>- /* .reserve = */ memtx_tree_index_reserve,
>+ /* .begin_build = */ memtx_tree_index_begin_build<1>,
>+ /* .reserve = */ memtx_tree_index_reserve<1>,
>  /* .build_next = */ memtx_tree_index_build_next_multikey,
>- /* .end_build = */ memtx_tree_index_end_build,
>+ /* .end_build = */ memtx_tree_index_end_build<1>,
> };
> 
> static const struct index_vtab memtx_tree_func_index_vtab = {
>- /* .destroy = */ memtx_tree_index_destroy,
>+ /* .destroy = */ memtx_tree_index_destroy<1>,
>  /* .commit_create = */ generic_index_commit_create,
>  /* .abort_create = */ generic_index_abort_create,
>  /* .commit_modify = */ generic_index_commit_modify,
>  /* .commit_drop = */ generic_index_commit_drop,
>- /* .update_def = */ memtx_tree_index_update_def,
>+ /* .update_def = */ memtx_tree_index_update_def<1>,
>  /* .depends_on_pk = */ memtx_tree_index_depends_on_pk,
>  /* .def_change_requires_rebuild = */
>  memtx_index_def_change_requires_rebuild,
>- /* .size = */ memtx_tree_index_size,
>- /* .bsize = */ memtx_tree_index_bsize,
>+ /* .size = */ memtx_tree_index_size<1>,
>+ /* .bsize = */ memtx_tree_index_bsize<1>,
>  /* .min = */ generic_index_min,
>  /* .max = */ generic_index_max,
>- /* .random = */ memtx_tree_index_random,
>- /* .count = */ memtx_tree_index_count,
>- /* .get = */ memtx_tree_index_get,
>+ /* .random = */ memtx_tree_index_random<1>,
>+ /* .count = */ memtx_tree_index_count<1>,
>+ /* .get = */ memtx_tree_index_get<1>,
>  /* .replace = */ memtx_tree_func_index_replace,
>- /* .create_iterator = */ memtx_tree_index_create_iterator,
>+ /* .create_iterator = */ memtx_tree_index_create_iterator<1>,
>  /* .create_snapshot_iterator = */
>- memtx_tree_index_create_snapshot_iterator,
>+ memtx_tree_index_create_snapshot_iterator<1>,
>  /* .stat = */ generic_index_stat,
>  /* .compact = */ generic_index_compact,
>  /* .reset_stat = */ generic_index_reset_stat,
>- /* .begin_build = */ memtx_tree_index_begin_build,
>- /* .reserve = */ memtx_tree_index_reserve,
>+ /* .begin_build = */ memtx_tree_index_begin_build<1>,
>+ /* .reserve = */ memtx_tree_index_reserve<1>,
>  /* .build_next = */ memtx_tree_func_index_build_next,
>- /* .end_build = */ memtx_tree_index_end_build,
>+ /* .end_build = */ memtx_tree_index_end_build<1>,
> };
> 
> /**
>@@ -1459,7 +1644,7 @@ static const struct index_vtab memtx_tree_func_index_vtab = {
>  * key defintion is not completely initialized at that moment).
>  */
> static const struct index_vtab memtx_tree_disabled_index_vtab = {
>- /* .destroy = */ memtx_tree_index_destroy,
>+ /* .destroy = */ memtx_tree_index_destroy<1>,
>  /* .commit_create = */ generic_index_commit_create,
>  /* .abort_create = */ generic_index_abort_create,
>  /* .commit_modify = */ generic_index_commit_modify,
>@@ -1488,27 +1673,19 @@ static const struct index_vtab memtx_tree_disabled_index_vtab = {
>  /* .end_build = */ generic_index_end_build,
> };
> 
>-struct index *
>-memtx_tree_index_new(struct memtx_engine *memtx, struct index_def *def)
>+template <int USE_HINT>
>+static struct index *
>+memtx_tree_index_new_tpl(struct memtx_engine *memtx, struct index_def *def,
>+ const struct index_vtab *vtab)
> {
>- struct memtx_tree_index *index =
>- (struct memtx_tree_index *)calloc(1, sizeof(*index));
>+ struct memtx_tree_index<USE_HINT> *index =
>+ (struct memtx_tree_index<USE_HINT> *)
>+ calloc(1, sizeof(*index));
>  if (index == NULL) {
>  diag_set(OutOfMemory, sizeof(*index),
>  "malloc", "struct memtx_tree_index");
>  return NULL;
>  }
>- const struct index_vtab *vtab;
>- if (def->key_def->for_func_index) {
>- if (def->key_def->func_index_func == NULL)
>- vtab = &memtx_tree_disabled_index_vtab;
>- else
>- vtab = &memtx_tree_func_index_vtab;
>- } else if (def->key_def->is_multikey) {
>- vtab = &memtx_tree_index_multikey_vtab;
>- } else {
>- vtab = &memtx_tree_index_vtab;
>- }
>  if (index_create(&index->base, (struct engine *)memtx,
>  vtab, def) != 0) {
>  free(index);
>@@ -1524,3 +1701,23 @@ memtx_tree_index_new(struct memtx_engine *memtx, struct index_def *def)
>  memtx_index_extent_free, memtx);
>  return &index->base;
> }
>+
>+struct index *
>+memtx_tree_index_new(struct memtx_engine *memtx, struct index_def *def)
>+{
>+ const struct index_vtab *vtab;
>+ if (def->key_def->for_func_index) {
>+ if (def->key_def->func_index_func == NULL)
>+ vtab = &memtx_tree_disabled_index_vtab;
>+ else
>+ vtab = &memtx_tree_func_index_vtab;
>+ } else if (def->key_def->is_multikey) {
>+ vtab = &memtx_tree_index_multikey_vtab;
>+ } else if (def->opts.hint) {
>+ vtab = &memtx_tree_use_hint_index_vtab;
>+ } else {
>+ vtab = &memtx_tree_no_hint_index_vtab;
>+ return memtx_tree_index_new_tpl<0>(memtx, def, vtab);
>+ }
>+ return memtx_tree_index_new_tpl<1>(memtx, def, vtab);
>+}
>diff --git a/src/lib/salad/bps_tree.h b/src/lib/salad/bps_tree.h
>index ef5ae3d..0bb803a 100644
>--- a/src/lib/salad/bps_tree.h
>+++ b/src/lib/salad/bps_tree.h
>@@ -168,6 +168,17 @@
> 
> /* {{{ BPS-tree interface settings */
> /**
>+ * Optional namespace for structs and functions.
>+ * Is set, struct and functions will have BPS_TREE_NAMESPACE:: prefix.
>+ * For example one can #define BPS_TREE_NAMESPACE my along with
>+ * #define BPS_TREE_NAME _test, and use then
>+ * struct my::bps_tree_test my_tree;
>+ * my::bps_tree_test_create(&my_tree, ...);
>+ *
>+ * #define BPS_TREE_NAMESPACE
>+ */
>+
>+/**
>  * Custom name for structs and functions.
>  * Struct and functions will have bps_tree##BPS_TREE_NAME name or prefix.
>  * For example one can #define BPS_TREE_NAME _test, and use then
>@@ -300,6 +311,10 @@
> 
> /* }}} */
> 
>+#ifdef BPS_TREE_NAMESPACE
>+namespace BPS_TREE_NAMESPACE {
>+#endif
>+
> /* {{{ BPS-tree internal settings */
> typedef int16_t bps_tree_pos_t;
> typedef uint32_t bps_tree_block_id_t;
>@@ -6188,3 +6203,7 @@ bps_tree_debug_check_internal_functions(bool assertme)
> #undef bps_tree_debug_check_insert_and_move_to_left_inner
> 
> /* }}} */
>+
>+#ifdef BPS_TREE_NAMESPACE
>+} /* namespace BPS_TREE_NAMESPACE { */
>+#endif
>diff --git a/test/box/alter.result b/test/box/alter.result
>index 237c2d8..5b412a7 100644
>--- a/test/box/alter.result
>+++ b/test/box/alter.result
>@@ -680,8 +680,9 @@ s.index.pk
>   - type: unsigned
>     is_nullable: false
>     fieldno: 2
>- type: TREE
>+ hint: true
>   id: 0
>+ type: TREE
>   space_id: 731
>   name: pk
> ...
>@@ -710,9 +711,10 @@ s.index.pk
>   - type: unsigned
>     is_nullable: false
>     fieldno: 1
>- space_id: 731
>+ hint: true
>   id: 0
>   type: TREE
>+ space_id: 731
>   name: pk
> ...
> s.index.secondary
>@@ -722,8 +724,9 @@ s.index.secondary
>   - type: unsigned
>     is_nullable: false
>     fieldno: 2
>- type: TREE
>+ hint: true
>   id: 1
>+ type: TREE
>   space_id: 731
>   name: secondary
> ...
>@@ -1559,3 +1562,97 @@ assert(err:match('does not exist') ~= nil)
> ---
> - true
> ...
>+-- hint
>+s = box.schema.create_space('test');
>+---
>+...
>+s:create_index('test1', {type='tree', parts={{1, 'uint'}}}).hint
>+---
>+- true
>+...
>+s:create_index('test2', {type='tree', parts={{2, 'uint'}}, hint = true}).hint
>+---
>+- true
>+...
>+s:create_index('test3', {type='tree', parts={{3, 'uint'}}, hint = false}).hint
>+---
>+- false
>+...
>+s:create_index('test4', {type='tree', parts={{4, 'string'}}, hint = false}).hint
>+---
>+- false
>+...
>+s.index.test1.hint
>+---
>+- true
>+...
>+s.index.test2.hint
>+---
>+- true
>+...
>+s.index.test3.hint
>+---
>+- false
>+...
>+s.index.test4.hint
>+---
>+- false
>+...
>+N = 1000 box.begin() for i = 1,N do s:replace{i, i, i, '' .. i} end box.commit()
>+---
>+...
>+s.index.test1:bsize() == s.index.test2:bsize()
>+---
>+- true
>+...
>+s.index.test1:bsize() > s.index.test3:bsize()
>+---
>+- true
>+...
>+s.index.test1:bsize() > s.index.test4:bsize()
>+---
>+- true
>+...
>+s.index.test1:alter{hint=false}
>+---
>+...
>+s.index.test2:alter{hint=true}
>+---
>+...
>+s.index.test3:alter{name='test33', hint=false}
>+---
>+...
>+s.index.test4:alter{hint=true}
>+---
>+...
>+s.index.test1.hint
>+---
>+- false
>+...
>+s.index.test2.hint
>+---
>+- true
>+...
>+s.index.test33.hint
>+---
>+- false
>+...
>+s.index.test4.hint
>+---
>+- true
>+...
>+s.index.test1:bsize() < s.index.test2:bsize()
>+---
>+- true
>+...
>+s.index.test1:bsize() == s.index.test33:bsize()
>+---
>+- true
>+...
>+s.index.test1:bsize() < s.index.test4:bsize()
>+---
>+- true
>+...
>+s:drop()
>+---
>+...
>diff --git a/test/box/alter.test.lua b/test/box/alter.test.lua
>index abd08e2..2114186 100644
>--- a/test/box/alter.test.lua
>+++ b/test/box/alter.test.lua
>@@ -620,3 +620,37 @@ s:drop()
> s:alter({})
> ok, err = pcall(box.schema.space.alter, s.id, {})
> assert(err:match('does not exist') ~= nil)
>+
>+-- hint
>+s = box.schema.create_space('test');
>+s:create_index('test1', {type='tree', parts={{1, 'uint'}}}).hint
>+s:create_index('test2', {type='tree', parts={{2, 'uint'}}, hint = true}).hint
>+s:create_index('test3', {type='tree', parts={{3, 'uint'}}, hint = false}).hint
>+s:create_index('test4', {type='tree', parts={{4, 'string'}}, hint = false}).hint
>+
>+s.index.test1.hint
>+s.index.test2.hint
>+s.index.test3.hint
>+s.index.test4.hint
>+
>+N = 1000 box.begin() for i = 1,N do s:replace{i, i, i, '' .. i} end box.commit()
>+
>+s.index.test1:bsize() == s.index.test2:bsize()
>+s.index.test1:bsize() > s.index.test3:bsize()
>+s.index.test1:bsize() > s.index.test4:bsize()
>+
>+s.index.test1:alter{hint=false}
>+s.index.test2:alter{hint=true}
>+s.index.test3:alter{name='test33', hint=false}
>+s.index.test4:alter{hint=true}
>+
>+s.index.test1.hint
>+s.index.test2.hint
>+s.index.test33.hint
>+s.index.test4.hint
>+
>+s.index.test1:bsize() < s.index.test2:bsize()
>+s.index.test1:bsize() == s.index.test33:bsize()
>+s.index.test1:bsize() < s.index.test4:bsize()
>+
>+s:drop()
>\ No newline at end of file
>diff --git a/test/box/errinj.result b/test/box/errinj.result
>index 613d22c..b8c2476 100644
>--- a/test/box/errinj.result
>+++ b/test/box/errinj.result
>@@ -1774,9 +1774,10 @@ rtreespace:create_index('pk', {if_not_exists = true})
>   - type: unsigned
>     is_nullable: false
>     fieldno: 1
>+ hint: true
>   id: 0
>- space_id: 512
>   type: TREE
>+ space_id: 512
>   name: pk
> ...
> rtreespace:create_index('target', {type='rtree', dimension = 3, parts={2, 'array'},unique = false, if_not_exists = true,})
>diff --git a/test/box/tree_pk.result b/test/box/tree_pk.result
>index df3c78b..18cb607 100644
>--- a/test/box/tree_pk.result
>+++ b/test/box/tree_pk.result
>@@ -852,3 +852,317 @@ box.internal.collation.drop('test')
> box.internal.collation.drop('test-ci')
> ---
> ...
>+-- hints
>+s = box.schema.space.create('test')
>+---
>+...
>+s:create_index('test', {type = 'tree', hint = 'true'} )
>+---
>+- error: Illegal parameters, options parameter 'hint' should be of type boolean
>+...
>+s:create_index('test', {type = 'hash', hint = true} )
>+---
>+- error: 'Can''t create or modify index ''test'' in space ''test'': hint is only reasonable
>+ with memtx tree index'
>+...
>+s:create_index('test', {type = 'hash'}):alter({hint = true})
>+---
>+- error: 'Can''t create or modify index ''test'' in space ''test'': hint is only reasonable
>+ with memtx tree index'
>+...
>+s:create_index('multikey', {hint = true, parts = {{2, 'int', path = '[*]'}}})
>+---
>+- error: 'Can''t create or modify index ''multikey'' in space ''test'': multikey index
>+ can''t use hints'
>+...
>+s:create_index('multikey', {parts = {{2, 'int', path = '[*]'}}}):alter({hint = true})
>+---
>+- error: 'Can''t create or modify index ''multikey'' in space ''test'': multikey index
>+ can''t use hints'
>+...
>+lua_code = [[function(tuple) return {tuple[1] + tuple[2]} end]]
>+---
>+...
>+box.schema.func.create('s', {body = lua_code, is_deterministic = true, is_sandboxed = true})
>+---
>+...
>+s:create_index('func', {hint = true, func = box.func.s.id, parts = {{1, 'unsigned'}}})
>+---
>+- error: 'Can''t create or modify index ''func'' in space ''test'': functional index
>+ can''t use hints'
>+...
>+s:drop()
>+---
>+...
>+s = box.schema.space.create('test', {engine = 'vinyl'})
>+---
>+...
>+s:create_index('test', {type = 'tree', hint = true} )
>+---
>+- error: 'Can''t create or modify index ''test'' in space ''test'': hint is only reasonable
>+ with memtx tree index'
>+...
>+s:drop()
>+---
>+...
>+-- numeric hints
>+s1 = box.schema.space.create('test1')
>+---
>+...
>+s1:create_index('test', {type = 'tree', hint = false}).hint
>+---
>+- false
>+...
>+s2 = box.schema.space.create('test2')
>+---
>+...
>+s2:create_index('test', {type = 'tree'}).hint
>+---
>+- true
>+...
>+N = 2000
>+---
>+...
>+box.begin() for i = 1,N do local v = math.random(10 * N) s1:replace{v} s2:replace{v} end box.commit()
>+---
>+...
>+s1:count() == s2:count()
>+---
>+- true
>+...
>+good = true r1 = s1:select{} r2 = s2:select{}
>+---
>+...
>+if #r1 ~= #r2 then good = false end
>+---
>+...
>+for k,v in pairs(r1) do if r2[k][1] ~= v[1] then good = false end end
>+---
>+...
>+good
>+---
>+- true
>+...
>+r1 = nil r2 = nil
>+---
>+...
>+function diff(t1, t2) if t1 then return t1[1] ~= t2[1] else return t2 ~= nil end end
>+---
>+...
>+for i = 1, N * 10 do if diff(s1:get{i}, s2:get{i}) then good = false end end
>+---
>+...
>+good
>+---
>+- true
>+...
>+s1.index[0]:bsize() < s2.index[0]:bsize()
>+---
>+- true
>+...
>+s1.index[0]:alter{hint=true}
>+---
>+...
>+s1.index[0]:bsize() == s2.index[0]:bsize()
>+---
>+- true
>+...
>+s2.index[0]:alter{hint=false}
>+---
>+...
>+s1.index[0]:bsize() > s2.index[0]:bsize()
>+---
>+- true
>+...
>+s1.index[0]:alter{hint=false}
>+---
>+...
>+s1.index[0]:bsize() == s2.index[0]:bsize()
>+---
>+- true
>+...
>+s1:drop()
>+---
>+...
>+s2:drop()
>+---
>+...
>+-- string hints
>+s1 = box.schema.space.create('test1')
>+---
>+...
>+s1:create_index('test', {type = 'tree', parts = {1, 'str'}, hint = false}).hint
>+---
>+- false
>+...
>+s2 = box.schema.space.create('test2')
>+---
>+...
>+s2:create_index('test', {type = 'tree', parts = {1, 'str'}}).hint
>+---
>+- true
>+...
>+N = 1000
>+---
>+...
>+box.begin() for i = 1,N do local v = ''..math.random(10 * N) s1:replace{v} s2:replace{v} end box.commit()
>+---
>+...
>+s1:count() == s2:count()
>+---
>+- true
>+...
>+good = true r1 = s1:select{} r2 = s2:select{}
>+---
>+...
>+if #r1 ~= #r2 then good = false end
>+---
>+...
>+for k,v in pairs(r1) do if r2[k][1] ~= v[1] then good = false end end
>+---
>+...
>+good
>+---
>+- true
>+...
>+r1 = nil r2 = nil
>+---
>+...
>+function diff(t1, t2) if t1 then return t1[1] ~= t2[1] else return t2 ~= nil end end
>+---
>+...
>+for i = 1, N * 10 do v = ''..i if diff(s1:get{v}, s2:get{v}) then good = false end end
>+---
>+...
>+good
>+---
>+- true
>+...
>+s1.index[0]:bsize() < s2.index[0]:bsize()
>+---
>+- true
>+...
>+s1.index[0]:alter{hint=true}
>+---
>+...
>+s1.index[0]:bsize() == s2.index[0]:bsize()
>+---
>+- true
>+...
>+s2.index[0]:alter{hint=false}
>+---
>+...
>+s1.index[0]:bsize() > s2.index[0]:bsize()
>+---
>+- true
>+...
>+s1.index[0]:alter{hint=false}
>+---
>+...
>+s1.index[0]:bsize() == s2.index[0]:bsize()
>+---
>+- true
>+...
>+s1:drop()
>+---
>+...
>+s2:drop()
>+---
>+...
>+-- string with collation hints
>+s1 = box.schema.space.create('test1')
>+---
>+...
>+s1:create_index('test', {type = 'tree', parts = {{1, 'str', collation = 'Unicode'}}, hint = false}).hint
>+---
>+- false
>+...
>+s2 = box.schema.space.create('test2')
>+---
>+...
>+s2:create_index('test', {type = 'tree', parts = {{1, 'str', collation = 'Unicode'}}}).hint
>+---
>+- true
>+...
>+N = 1000
>+---
>+...
>+syms = {'a', 'B', 'c', 'D', 'ж', 'Ё', '~', '1', '%', '2'}
>+---
>+...
>+syms_size = #syms
>+---
>+...
>+len = 20
>+---
>+...
>+vals = {}
>+---
>+...
>+for i = 1,2*N do str = '' for j=1,len do str = str .. syms[math.random(syms_size)] end vals[i] = str end
>+---
>+...
>+for i = 1,N do local v = vals[i] s1:replace{v} s2:replace{v} end
>+---
>+...
>+s1:count() == s2:count()
>+---
>+- true
>+...
>+good = true r1 = s1:select{} r2 = s2:select{}
>+---
>+...
>+if #r1 ~= #r2 then good = false end
>+---
>+...
>+for k,v in pairs(r1) do if r2[k][1] ~= v[1] then good = false end end
>+---
>+...
>+good
>+---
>+- true
>+...
>+r1 = nil r2 = nil
>+---
>+...
>+function diff(t1, t2) if t1 then return t1[1] ~= t2[1] else return t2 ~= nil end end
>+---
>+...
>+for i = 1, N * 2 do v = vals[i] if diff(s1:get{v}, s2:get{v}) then good = false end end
>+---
>+...
>+good
>+---
>+- true
>+...
>+s1.index[0]:bsize() < s2.index[0]:bsize()
>+---
>+- true
>+...
>+s1.index[0]:alter{hint=true}
>+---
>+...
>+s1.index[0]:bsize() == s2.index[0]:bsize()
>+---
>+- true
>+...
>+s2.index[0]:alter{hint=false}
>+---
>+...
>+s1.index[0]:bsize() > s2.index[0]:bsize()
>+---
>+- true
>+...
>+s1.index[0]:alter{hint=false}
>+---
>+...
>+s1.index[0]:bsize() == s2.index[0]:bsize()
>+---
>+- true
>+...
>+s1:drop()
>+---
>+...
>+s2:drop()
>+---
>+...
>diff --git a/test/box/tree_pk.test.lua b/test/box/tree_pk.test.lua
>index 1190ab4..2f22ed9 100644
>--- a/test/box/tree_pk.test.lua
>+++ b/test/box/tree_pk.test.lua
>@@ -301,3 +301,118 @@ s:drop()
> 
> box.internal.collation.drop('test')
> box.internal.collation.drop('test-ci')
>+
>+-- hints
>+s = box.schema.space.create('test')
>+s:create_index('test', {type = 'tree', hint = 'true'} )
>+s:create_index('test', {type = 'hash', hint = true} )
>+s:create_index('test', {type = 'hash'}):alter({hint = true})
>+s:create_index('multikey', {hint = true, parts = {{2, 'int', path = '[*]'}}})
>+s:create_index('multikey', {parts = {{2, 'int', path = '[*]'}}}):alter({hint = true})
>+lua_code = [[function(tuple) return {tuple[1] + tuple[2]} end]]
>+box.schema.func.create('s', {body = lua_code, is_deterministic = true, is_sandboxed = true})
>+s:create_index('func', {hint = true, func = box.func.s.id, parts = {{1, 'unsigned'}}})
>+s:drop()
>+
>+s = box.schema.space.create('test', {engine = 'vinyl'})
>+s:create_index('test', {type = 'tree', hint = true} )
>+s:drop()
>+
>+-- numeric hints
>+s1 = box.schema.space.create('test1')
>+s1:create_index('test', {type = 'tree', hint = false}).hint
>+s2 = box.schema.space.create('test2')
>+s2:create_index('test', {type = 'tree'}).hint
>+
>+N = 2000
>+box.begin() for i = 1,N do local v = math.random(10 * N) s1:replace{v} s2:replace{v} end box.commit()
>+s1:count() == s2:count()
>+
>+good = true r1 = s1:select{} r2 = s2:select{}
>+if #r1 ~= #r2 then good = false end
>+for k,v in pairs(r1) do if r2[k][1] ~= v[1] then good = false end end
>+good
>+r1 = nil r2 = nil
>+
>+function diff(t1, t2) if t1 then return t1[1] ~= t2[1] else return t2 ~= nil end end
>+for i = 1, N * 10 do if diff(s1:get{i}, s2:get{i}) then good = false end end
>+good
>+
>+s1.index[0]:bsize() < s2.index[0]:bsize()
>+s1.index[0]:alter{hint=true}
>+s1.index[0]:bsize() == s2.index[0]:bsize()
>+s2.index[0]:alter{hint=false}
>+s1.index[0]:bsize() > s2.index[0]:bsize()
>+s1.index[0]:alter{hint=false}
>+s1.index[0]:bsize() == s2.index[0]:bsize()
>+
>+s1:drop()
>+s2:drop()
>+
>+-- string hints
>+s1 = box.schema.space.create('test1')
>+s1:create_index('test', {type = 'tree', parts = {1, 'str'}, hint = false}).hint
>+s2 = box.schema.space.create('test2')
>+s2:create_index('test', {type = 'tree', parts = {1, 'str'}}).hint
>+
>+N = 1000
>+box.begin() for i = 1,N do local v = ''..math.random(10 * N) s1:replace{v} s2:replace{v} end box.commit()
>+s1:count() == s2:count()
>+
>+good = true r1 = s1:select{} r2 = s2:select{}
>+if #r1 ~= #r2 then good = false end
>+for k,v in pairs(r1) do if r2[k][1] ~= v[1] then good = false end end
>+good
>+r1 = nil r2 = nil
>+
>+function diff(t1, t2) if t1 then return t1[1] ~= t2[1] else return t2 ~= nil end end
>+for i = 1, N * 10 do v = ''..i if diff(s1:get{v}, s2:get{v}) then good = false end end
>+good
>+
>+s1.index[0]:bsize() < s2.index[0]:bsize()
>+s1.index[0]:alter{hint=true}
>+s1.index[0]:bsize() == s2.index[0]:bsize()
>+s2.index[0]:alter{hint=false}
>+s1.index[0]:bsize() > s2.index[0]:bsize()
>+s1.index[0]:alter{hint=false}
>+s1.index[0]:bsize() == s2.index[0]:bsize()
>+
>+s1:drop()
>+s2:drop()
>+
>+-- string with collation hints
>+s1 = box.schema.space.create('test1')
>+s1:create_index('test', {type = 'tree', parts = {{1, 'str', collation = 'Unicode'}}, hint = false}).hint
>+s2 = box.schema.space.create('test2')
>+s2:create_index('test', {type = 'tree', parts = {{1, 'str', collation = 'Unicode'}}}).hint
>+
>+N = 1000
>+syms = {'a', 'B', 'c', 'D', 'ж', 'Ё', '~', '1', '%', '2'}
>+syms_size = #syms
>+len = 20
>+vals = {}
>+for i = 1,2*N do str = '' for j=1,len do str = str .. syms[math.random(syms_size)] end vals[i] = str end
>+
>+for i = 1,N do local v = vals[i] s1:replace{v} s2:replace{v} end
>+s1:count() == s2:count()
>+
>+good = true r1 = s1:select{} r2 = s2:select{}
>+if #r1 ~= #r2 then good = false end
>+for k,v in pairs(r1) do if r2[k][1] ~= v[1] then good = false end end
>+good
>+r1 = nil r2 = nil
>+
>+function diff(t1, t2) if t1 then return t1[1] ~= t2[1] else return t2 ~= nil end end
>+for i = 1, N * 2 do v = vals[i] if diff(s1:get{v}, s2:get{v}) then good = false end end
>+good
>+
>+s1.index[0]:bsize() < s2.index[0]:bsize()
>+s1.index[0]:alter{hint=true}
>+s1.index[0]:bsize() == s2.index[0]:bsize()
>+s2.index[0]:alter{hint=false}
>+s1.index[0]:bsize() > s2.index[0]:bsize()
>+s1.index[0]:alter{hint=false}
>+s1.index[0]:bsize() == s2.index[0]:bsize()
>+
>+s1:drop()
>+s2:drop()
>diff --git a/test/box/tree_pk_multipart.result b/test/box/tree_pk_multipart.result
>index 93219f6..3f6bb94 100644
>--- a/test/box/tree_pk_multipart.result
>+++ b/test/box/tree_pk_multipart.result
>@@ -542,3 +542,156 @@ space:drop()
> space = nil
> ---
> ...
>+-- hints
>+test_run:cmd("setopt delimiter ';'")
>+---
>+- true
>+...
>+function equal(res1, res2)
>+ if #res1 ~= #res2 then
>+ return false
>+ end
>+ for k,v in pairs(res1) do
>+ if res2[k][1] ~= v[1] or res2[k][2] ~= v[2] then
>+ return false
>+ end
>+ end
>+ return true
>+end
>+test_run:cmd("setopt delimiter ''");
>+---
>+...
>+-- num num
>+N1 = 100
>+---
>+...
>+t1 = {}
>+---
>+...
>+for i = 1,N1*2 do t1[i] = math.random(10000) * 10000 + i end
>+---
>+...
>+N2 = 5
>+---
>+...
>+t2 = {}
>+---
>+...
>+for i = 1,N2*2 do t2[i] = math.random(1000000) end
>+---
>+...
>+s1 = box.schema.space.create('test1')
>+---
>+...
>+s1:create_index('test', {type = 'tree', parts = {{1, 'num'}, {2, 'num'}}, hint = false}).hint
>+---
>+- false
>+...
>+s2 = box.schema.space.create('test2')
>+---
>+...
>+s2:create_index('test', {type = 'tree', parts = {{1, 'num'}, {2, 'num'}}, hint = true}).hint
>+---
>+- true
>+...
>+for j = 1,N2 do for i = 1,N1 do s1:replace{t1[i], t2[j]} s2:replace{t1[i], t2[j]} end end
>+---
>+...
>+s1:count() == s2:count()
>+---
>+- true
>+...
>+equal(s1:select{}, s2:select{})
>+---
>+- true
>+...
>+good = true
>+---
>+...
>+for i = 1,N1*2 do good = good and equal(s1:select{t1[i]}, s2:select{t1[i]}) end
>+---
>+...
>+good
>+---
>+- true
>+...
>+for i = 1,N1*2 do for j=1,N2*2 do good = good and equal(s1:select{t1[i], t2[j]}, s2:select{t1[i], t2[j]}) end end
>+---
>+...
>+good
>+---
>+- true
>+...
>+s1:drop()
>+---
>+...
>+s2:drop()
>+---
>+...
>+-- str num
>+N1 = 100
>+---
>+...
>+t1 = {}
>+---
>+...
>+for i = 1,N1*2 do t1[i] = ''..(math.random(10000) * 10000 + i) end
>+---
>+...
>+N2 = 5
>+---
>+...
>+t2 = {}
>+---
>+...
>+for i = 1,N2*2 do t2[i] = math.random(1000000) end
>+---
>+...
>+s1 = box.schema.space.create('test1')
>+---
>+...
>+s1:create_index('test', {type = 'tree', parts = {{1, 'str'}, {2, 'num'}}, hint = false}).hint
>+---
>+- false
>+...
>+s2 = box.schema.space.create('test2')
>+---
>+...
>+s2:create_index('test', {type = 'tree', parts = {{1, 'str'}, {2, 'num'}}, hint = true}).hint
>+---
>+- true
>+...
>+for j = 1,N2 do for i = 1,N1 do s1:replace{t1[i], t2[j]} s2:replace{t1[i], t2[j]} end end
>+---
>+...
>+s1:count() == s2:count()
>+---
>+- true
>+...
>+equal(s1:select{}, s2:select{})
>+---
>+- true
>+...
>+good = true
>+---
>+...
>+for i = 1,N1*2 do good = good and equal(s1:select{t1[i]}, s2:select{t1[i]}) end
>+---
>+...
>+good
>+---
>+- true
>+...
>+for i = 1,N1*2 do for j=1,N2*2 do good = good and equal(s1:select{t1[i], t2[j]}, s2:select{t1[i], t2[j]}) end end
>+---
>+...
>+good
>+---
>+- true
>+...
>+s1:drop()
>+---
>+...
>+s2:drop()
>+---
>+...
>diff --git a/test/box/tree_pk_multipart.test.lua b/test/box/tree_pk_multipart.test.lua
>index 7d3405f..cba3a98 100644
>--- a/test/box/tree_pk_multipart.test.lua
>+++ b/test/box/tree_pk_multipart.test.lua
>@@ -194,3 +194,67 @@ test_run:cmd("setopt delimiter ''");
> space:drop()
> 
> space = nil
>+
>+
>+-- hints
>+test_run:cmd("setopt delimiter ';'")
>+function equal(res1, res2)
>+ if #res1 ~= #res2 then
>+ return false
>+ end
>+ for k,v in pairs(res1) do
>+ if res2[k][1] ~= v[1] or res2[k][2] ~= v[2] then
>+ return false
>+ end
>+ end
>+ return true
>+end
>+test_run:cmd("setopt delimiter ''");
>+
>+-- num num
>+N1 = 100
>+t1 = {}
>+for i = 1,N1*2 do t1[i] = math.random(10000) * 10000 + i end
>+N2 = 5
>+t2 = {}
>+for i = 1,N2*2 do t2[i] = math.random(1000000) end
>+
>+s1 = box.schema.space.create('test1')
>+s1:create_index('test', {type = 'tree', parts = {{1, 'num'}, {2, 'num'}}, hint = false}).hint
>+s2 = box.schema.space.create('test2')
>+s2:create_index('test', {type = 'tree', parts = {{1, 'num'}, {2, 'num'}}, hint = true}).hint
>+for j = 1,N2 do for i = 1,N1 do s1:replace{t1[i], t2[j]} s2:replace{t1[i], t2[j]} end end
>+s1:count() == s2:count()
>+equal(s1:select{}, s2:select{})
>+good = true
>+for i = 1,N1*2 do good = good and equal(s1:select{t1[i]}, s2:select{t1[i]}) end
>+good
>+for i = 1,N1*2 do for j=1,N2*2 do good = good and equal(s1:select{t1[i], t2[j]}, s2:select{t1[i], t2[j]}) end end
>+good
>+
>+s1:drop()
>+s2:drop()
>+
>+-- str num
>+N1 = 100
>+t1 = {}
>+for i = 1,N1*2 do t1[i] = ''..(math.random(10000) * 10000 + i) end
>+N2 = 5
>+t2 = {}
>+for i = 1,N2*2 do t2[i] = math.random(1000000) end
>+
>+s1 = box.schema.space.create('test1')
>+s1:create_index('test', {type = 'tree', parts = {{1, 'str'}, {2, 'num'}}, hint = false}).hint
>+s2 = box.schema.space.create('test2')
>+s2:create_index('test', {type = 'tree', parts = {{1, 'str'}, {2, 'num'}}, hint = true}).hint
>+for j = 1,N2 do for i = 1,N1 do s1:replace{t1[i], t2[j]} s2:replace{t1[i], t2[j]} end end
>+s1:count() == s2:count()
>+equal(s1:select{}, s2:select{})
>+good = true
>+for i = 1,N1*2 do good = good and equal(s1:select{t1[i]}, s2:select{t1[i]}) end
>+good
>+for i = 1,N1*2 do for j=1,N2*2 do good = good and equal(s1:select{t1[i], t2[j]}, s2:select{t1[i], t2[j]}) end end
>+good
>+
>+s1:drop()
>+s2:drop()
>--
>2.7.4
> 
--
Ilya Kosarev