Fix memory leak in SnapBuildSerialize.

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: [email protected]
Diagnosed-by: [email protected]
Author: Amit Kapila
Backpatch-through: 9.5
Discussion: https://postgr.es/m/033ab54c-6393-42ee-8ec9-2b399b5d8cde[email protected]

diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c
index 3e9d4cd79f95622cc8e3eaedfba7fa37271edce4..4ec0003550e4f858b0a0430e794f0c65afc449f7 100644 (file)
--- a/src/backend/replication/logical/snapbuild.c
+++ b/src/backend/replication/logical/snapbuild.c
@@ -1485,7 +1485,7 @@ static void
 SnapBuildSerialize(SnapBuild *builder, XLogRecPtr lsn)
 {
    Size        needed_length;
-   SnapBuildOnDisk *ondisk;
+   SnapBuildOnDisk *ondisk = NULL;
    char       *ondisk_c;
    int         fd;
    char        tmppath[MAXPGPATH];
@@ -1684,6 +1684,9 @@ SnapBuildSerialize(SnapBuild *builder, XLogRecPtr lsn)
 out:
    ReorderBufferSetRestartPoint(builder->reorder,
                                 builder->last_serialized_snapshot);
+   /* be tidy */
+   if (ondisk)
+       pfree(ondisk);
 }
 
 /*