Fix memory leak in SnapBuildSerialize.

Amit Kapila · Amit Kapila · commit 4bccceaa9179 · 2021-01-13T09:22:03.000+05:30
The memory for the snapshot was leaked while serializing it to disk during logical decoding. This memory will be freed only once walsender stops streaming the changes. This can lead to a huge memory increase when master logs Standby Snapshot too frequently say when the user is trying to create many replication slots. Reported-by: funnyxj.fxj@alibaba-inc.com Diagnosed-by: funnyxj.fxj@alibaba-inc.com Author: Amit Kapila Backpatch-through: 9.5 Discussion: https://postgr.es/m/033ab54c-6393-42ee-8ec9-2b399b5d8cde.funnyxj.fxj@alibaba-inc.com
diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c
@@ -1447,7 +1447,7 @@ static void
 SnapBuildSerialize(SnapBuild *builder, XLogRecPtr lsn)
 {
 	Size		needed_length;
-	SnapBuildOnDisk *ondisk;
+	SnapBuildOnDisk *ondisk = NULL;
 	char	   *ondisk_c;
 	int			fd;
 	char		tmppath[MAXPGPATH];
@@ -1639,6 +1639,9 @@ SnapBuildSerialize(SnapBuild *builder, XLogRecPtr lsn)
 out:
 	ReorderBufferSetRestartPoint(builder->reorder,
 								 builder->last_serialized_snapshot);
+	/* be tidy */
+	if (ondisk)
+		pfree(ondisk);
 }
 
 /*
