[Tarantool-patches] [PATCH 2/3] memtx: don't reserve extra memory if not needed

[Ilya Kosarev <i.kosarev@tarantool.org>]

memtx_index_extent_reserve was always being called from
memtx_space_replace_all_keys. It could lead to slab allocator failure
while reaching memtx_memory limit, which is especially distressing on
space:truncate() and space:delete() invocations. we  Now it is not
being called if not needed, including space:truncate() and
space:delete() cases.

Part of #3807
---
 src/box/memtx_space.c | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/src/box/memtx_space.c b/src/box/memtx_space.c
index 6ef84e04564..1e8759778e7 100644
--- a/src/box/memtx_space.c
+++ b/src/box/memtx_space.c
@@ -260,10 +260,18 @@ memtx_space_replace_all_keys(struct space *space, struct tuple *old_tuple,
 	 * Ensure we have enough slack memory to guarantee
 	 * successful statement-level rollback.
 	 */
-	if (memtx_index_extent_reserve(memtx, new_tuple != NULL ?
-				       RESERVE_EXTENTS_BEFORE_REPLACE :
-				       RESERVE_EXTENTS_BEFORE_DELETE) != 0)
+	if (space->index_count > 1 && new_tuple != NULL) {
+		if (memtx_index_extent_reserve(memtx, new_tuple != NULL ?
+					       RESERVE_EXTENTS_BEFORE_REPLACE :
+					       RESERVE_EXTENTS_BEFORE_DELETE) != 0)
+			return -1;
+	}
+	ERROR_INJECT(ERRINJ_INDEX_ALLOC, {
+		/* same error as in mempool_alloc */
+		diag_set(OutOfMemory, MEMTX_EXTENT_SIZE,
+			 "mempool", "new slab");
 		return -1;
+	});
 
 	uint32_t i = 0;
 
-- 
2.17.1