[RFC PATCH 02/23] vinyl: always get full tuple from pk after reading from secondary index

[Vladimir Davydov <vdavydov.dev@gmail.com>]

Currently, we don't always need a full tuple. Sometimes (e.g. for
checking uniqueness constraint), a partial tuple read from a secondary
index is enough. So we have vy_lsm_get() which reads a partial tuple
from an index. However, once the optimization described in #2129 is
implemented, it might happen that a tuple read from a secondary index
was overwritten or deleted in the primary index, but DELETE statement
hasn't been propagated to the secondary index yet, i.e. we will have to
read the primary index anyway, even if we don't need a full tuple.

That said, let us:

 - Make vy_lsm_get() always fetch a full tuple, even for secondary
   indexes, and rename it to vy_get().

 - Rewrite vy_lsm_full_by_key() as a wrapper around vy_get() and rename
   it to vy_get_by_raw_key().

 - Introduce vy_get_by_secondary_tuple() which gets a full tuple given a
   tuple read from a secondary index. For now, it's basically a call to
   vy_point_lookup(), but it'll become a bit more complex once #2129 is
   implemented.

 - Prepare vy_get() for the fact that a tuple read from a secondary
   index may be absent in the primary index, in which case it should
   try the next matching one.

Needed for #2129
---
 src/box/vinyl.c | 204 ++++++++++++++++++++++++++++++++------------------------
 1 file changed, 118 insertions(+), 86 deletions(-)

diff --git a/src/box/vinyl.c b/src/box/vinyl.c
index f9c2843e..64004226 100644
--- a/src/box/vinyl.c
+++ b/src/box/vinyl.c
@@ -1265,7 +1265,48 @@ vy_is_committed(struct vy_env *env, struct space *space)
 }
 
 /**
- * Get a vinyl tuple from the LSM tree by the key.
+ * Get a full tuple by a tuple read from a secondary index.
+ * @param lsm         LSM tree from which the tuple was read.
+ * @param tx          Current transaction.
+ * @param rv          Read view.
+ * @param tuple       Tuple read from a secondary index.
+ * @param[out] result The found tuple is stored here. Must be
+ *                    unreferenced after usage.
+ *
+ * @param  0 Success.
+ * @param -1 Memory error or read error.
+ */
+static int
+vy_get_by_secondary_tuple(struct vy_lsm *lsm, struct vy_tx *tx,
+			  const struct vy_read_view **rv,
+			  struct tuple *tuple, struct tuple **result)
+{
+	assert(lsm->index_id > 0);
+	/*
+	 * No need in vy_tx_track() as the tuple must already be
+	 * tracked in the secondary index LSM tree.
+	 */
+	if (vy_point_lookup(lsm->pk, tx, rv, tuple, result) != 0)
+		return -1;
+
+	if (*result == NULL) {
+		/*
+		 * All indexes of a space must be consistent, i.e.
+		 * if a tuple is present in one index, it must be
+		 * present in all other indexes as well, so we can
+		 * get here only if there's a bug somewhere in vinyl.
+		 * Don't abort as core dump won't really help us in
+		 * this case. Just warn the user and proceed to the
+		 * next tuple.
+		 */
+		say_warn("%s: key %s missing in primary index",
+			 vy_lsm_name(lsm), vy_stmt_str(tuple));
+	}
+	return 0;
+}
+
+/**
+ * Get a tuple from a vinyl space by key.
  * @param lsm         LSM tree in which search.
  * @param tx          Current transaction.
  * @param rv          Read view.
@@ -1276,10 +1317,10 @@ vy_is_committed(struct vy_env *env, struct space *space)
  * @param  0 Success.
  * @param -1 Memory error or read error.
  */
-static inline int
-vy_lsm_get(struct vy_lsm *lsm, struct vy_tx *tx,
-	     const struct vy_read_view **rv,
-	     struct tuple *key, struct tuple **result)
+static int
+vy_get(struct vy_lsm *lsm, struct vy_tx *tx,
+       const struct vy_read_view **rv,
+       struct tuple *key, struct tuple **result)
 {
 	/*
 	 * tx can be NULL, for example, if an user calls
@@ -1287,22 +1328,75 @@ vy_lsm_get(struct vy_lsm *lsm, struct vy_tx *tx,
 	 */
 	assert(tx == NULL || tx->state == VINYL_TX_READY);
 
+	int rc;
+	struct tuple *tuple;
+
 	if (tuple_field_count(key) >= lsm->cmp_def->part_count) {
+		/*
+		 * Use point lookup for a full key.
+		 */
 		if (tx != NULL && vy_tx_track_point(tx, lsm, key) != 0)
 			return -1;
-		return vy_point_lookup(lsm, tx, rv, key, result);
+		if (vy_point_lookup(lsm, tx, rv, key, &tuple) != 0)
+			return -1;
+		if (lsm->index_id > 0 && tuple != NULL) {
+			rc = vy_get_by_secondary_tuple(lsm, tx, rv,
+						       tuple, result);
+			tuple_unref(tuple);
+			if (rc != 0)
+				return -1;
+		} else {
+			*result = tuple;
+		}
+		return 0;
 	}
 
 	struct vy_read_iterator itr;
 	vy_read_iterator_open(&itr, lsm, tx, ITER_EQ, key, rv);
-	int rc = vy_read_iterator_next(&itr, result);
-	if (*result != NULL)
-		tuple_ref(*result);
+	while ((rc = vy_read_iterator_next(&itr, &tuple)) == 0) {
+		if (lsm->index_id == 0 || tuple == NULL) {
+			*result = tuple;
+			if (tuple != NULL)
+				tuple_ref(tuple);
+			break;
+		}
+		rc = vy_get_by_secondary_tuple(lsm, tx, rv, tuple, result);
+		if (rc != 0 || *result != NULL)
+			break;
+	}
 	vy_read_iterator_close(&itr);
 	return rc;
 }
 
 /**
+ * Get a tuple from a vinyl space by raw key.
+ * @param lsm         LSM tree in which search.
+ * @param tx          Current transaction.
+ * @param rv          Read view.
+ * @param key_raw     MsgPack array of key fields.
+ * @param part_count  Count of parts in the key.
+ * @param[out] result The found tuple is stored here. Must be
+ *                    unreferenced after usage.
+ *
+ * @param  0 Success.
+ * @param -1 Memory error or read error.
+ */
+static int
+vy_get_by_raw_key(struct vy_lsm *lsm, struct vy_tx *tx,
+		  const struct vy_read_view **rv,
+		  const char *key_raw, uint32_t part_count,
+		  struct tuple **result)
+{
+	struct tuple *key = vy_stmt_new_select(lsm->env->key_format,
+					       key_raw, part_count);
+	if (key == NULL)
+		return -1;
+	int rc = vy_get(lsm, tx, rv, key, result);
+	tuple_unref(key);
+	return rc;
+}
+
+/**
  * Check if the LSM tree contains the key. If true, then set
  * a duplicate key error in the diagnostics area.
  * @param env        Vinyl environment.
@@ -1329,7 +1423,7 @@ vy_check_is_unique(struct vy_env *env, struct vy_tx *tx,
 	 */
 	if (env->status != VINYL_ONLINE)
 		return 0;
-	if (vy_lsm_get(lsm, tx, rv, key, &found))
+	if (vy_get(lsm, tx, rv, key, &found))
 		return -1;
 
 	if (found) {
@@ -1480,8 +1574,8 @@ vy_replace_one(struct vy_env *env, struct vy_tx *tx, struct space *space,
 	 * old tuple to pass it to the trigger.
 	 */
 	if (stmt != NULL && !rlist_empty(&space->on_replace)) {
-		if (vy_lsm_get(pk, tx, vy_tx_read_view(tx),
-			       new_tuple, &stmt->old_tuple) != 0)
+		if (vy_get(pk, tx, vy_tx_read_view(tx),
+			   new_tuple, &stmt->old_tuple) != 0)
 			goto error_unref;
 	}
 	if (vy_tx_set(tx, pk, new_tuple))
@@ -1536,8 +1630,7 @@ vy_replace_impl(struct vy_env *env, struct vy_tx *tx, struct space *space,
 		return -1;
 
 	/* Get full tuple from the primary index. */
-	if (vy_lsm_get(pk, tx, vy_tx_read_view(tx),
-			 new_stmt, &old_stmt) != 0)
+	if (vy_get(pk, tx, vy_tx_read_view(tx), new_stmt, &old_stmt) != 0)
 		goto error;
 
 	/*
@@ -1628,51 +1721,6 @@ vy_unique_key_validate(struct vy_lsm *lsm, const char *key,
 }
 
 /**
- * Find a tuple in the primary index LSM tree by the key of the
- * specified LSM tree.
- * @param lsm         LSM tree for which the key is specified.
- *                    Can be both primary and secondary.
- * @param tx          Current transaction.
- * @param rv          Read view.
- * @param key_raw     MessagePack'ed data, the array without a
- *                    header.
- * @param part_count  Count of parts in the key.
- * @param[out] result The found statement is stored here. Must be
- *                    unreferenced after usage.
- *
- * @retval  0 Success.
- * @retval -1 Memory error.
- */
-static inline int
-vy_lsm_full_by_key(struct vy_lsm *lsm, struct vy_tx *tx,
-		   const struct vy_read_view **rv,
-		   const char *key_raw, uint32_t part_count,
-		   struct tuple **result)
-{
-	int rc;
-	struct tuple *key = vy_stmt_new_select(lsm->env->key_format,
-					       key_raw, part_count);
-	if (key == NULL)
-		return -1;
-	struct tuple *found;
-	rc = vy_lsm_get(lsm, tx, rv, key, &found);
-	tuple_unref(key);
-	if (rc != 0)
-		return -1;
-	if (lsm->index_id == 0 || found == NULL) {
-		*result = found;
-		return 0;
-	}
-	/*
-	 * No need in vy_tx_track() as the tuple is already
-	 * tracked in the secondary index LSM tree.
-	 */
-	rc = vy_point_lookup(lsm->pk, tx, rv, found, result);
-	tuple_unref(found);
-	return rc;
-}
-
-/**
  * Delete the tuple from all LSM trees of the vinyl space.
  * @param env        Vinyl environment.
  * @param tx         Current transaction.
@@ -1754,8 +1802,8 @@ vy_delete(struct vy_env *env, struct vy_tx *tx, struct txn_stmt *stmt,
 	 *   and pass them to indexes for deletion.
 	 */
 	if (has_secondary || !rlist_empty(&space->on_replace)) {
-		if (vy_lsm_full_by_key(lsm, tx, vy_tx_read_view(tx),
-				key, part_count, &stmt->old_tuple) != 0)
+		if (vy_get_by_raw_key(lsm, tx, vy_tx_read_view(tx),
+				      key, part_count, &stmt->old_tuple) != 0)
 			return -1;
 		if (stmt->old_tuple == NULL)
 			return 0;
@@ -1836,8 +1884,8 @@ vy_update(struct vy_env *env, struct vy_tx *tx, struct txn_stmt *stmt,
 	if (vy_unique_key_validate(lsm, key, part_count))
 		return -1;
 
-	if (vy_lsm_full_by_key(lsm, tx, vy_tx_read_view(tx),
-			       key, part_count, &stmt->old_tuple) != 0)
+	if (vy_get_by_raw_key(lsm, tx, vy_tx_read_view(tx),
+			      key, part_count, &stmt->old_tuple) != 0)
 		return -1;
 	/* Nothing to update. */
 	if (stmt->old_tuple == NULL)
@@ -2110,8 +2158,7 @@ vy_upsert(struct vy_env *env, struct vy_tx *tx, struct txn_stmt *stmt,
 					pk->key_def, pk->env->key_format);
 	if (key == NULL)
 		return -1;
-	int rc = vy_lsm_get(pk, tx, vy_tx_read_view(tx),
-			      key, &stmt->old_tuple);
+	int rc = vy_get(pk, tx, vy_tx_read_view(tx), key, &stmt->old_tuple);
 	tuple_unref(key);
 	if (rc != 0)
 		return -1;
@@ -3910,28 +3957,13 @@ next:
 			fiber_sleep(0.01);
 	}
 #endif
-	/*
-	 * Get the full tuple from the primary index.
-	 * Note, there's no need in vy_tx_track() as the
-	 * tuple is already tracked in the secondary index.
-	 */
-	if (vy_point_lookup(it->lsm->pk, it->tx, vy_tx_read_view(it->tx),
-			    tuple, ret) != 0)
+	/* Get the full tuple from the primary index. */
+	if (vy_get_by_secondary_tuple(it->lsm, it->tx,
+				      vy_tx_read_view(it->tx),
+				      tuple, ret) != 0)
 		goto fail;
-	if (*ret == NULL) {
-		/*
-		 * All indexes of a space must be consistent, i.e.
-		 * if a tuple is present in one index, it must be
-		 * present in all other indexes as well, so we can
-		 * get here only if there's a bug somewhere in vinyl.
-		 * Don't abort as core dump won't really help us in
-		 * this case. Just warn the user and proceed to the
-		 * next tuple.
-		 */
-		say_warn("%s: key %s missing in primary index",
-			 vy_lsm_name(it->lsm), vy_stmt_str(tuple));
+	if (*ret == NULL)
 		goto next;
-	}
 	tuple_bless(*ret);
 	tuple_unref(*ret);
 	return 0;
@@ -4020,7 +4052,7 @@ vinyl_index_get(struct index *index, const char *key,
 	const struct vy_read_view **rv = (tx != NULL ? vy_tx_read_view(tx) :
 					  &env->xm->p_global_read_view);
 
-	if (vy_lsm_full_by_key(lsm, tx, rv, key, part_count, ret) != 0)
+	if (vy_get_by_raw_key(lsm, tx, rv, key, part_count, ret) != 0)
 		return -1;
 	if (*ret != NULL) {
 		tuple_bless(*ret);
-- 
2.11.0