Re: Adding REPACK [concurrently]

Srinath Reddy Sadipiralla <srinath2133(at)gmail(dot)com> wrote:

> Hi Tom,
>
> On Tue, Apr 7, 2026 at 10:14 AM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>
> Maybe you saw this already, but BF member skink is failing on
> src/test/modules/injection_points/specs/repack.spec:
>
> https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=skink&dt=2026-04-06%2022%3A50%3A41
>
> i looked into this , it seems like valgrind catches the uninitialised padding bytes, which
> repack worker is writing using BufFileWrite, it seems this fix solved the problem.
>
> diff --git a/src/backend/utils/time/snapmgr.c b/src/backend/utils/time/snapmgr.c
> index 2e6197f5f35..f5682b87626 100644
> --- a/src/backend/utils/time/snapmgr.c
> +++ b/src/backend/utils/time/snapmgr.c
> @@ -1739,6 +1739,8 @@ SerializeSnapshot(Snapshot snapshot, char *start_address)
>
> Assert(snapshot->subxcnt >= 0);
>
> + MemSet(&serialized_snapshot, 0, sizeof(SerializedSnapshotData));
> +
> /* Copy all required fields */
> serialized_snapshot.xmin = snapshot->xmin;
> serialized_snapshot.xmax = snapshot->xmax;
>
> thoughts?

Could you reproduce the failure in your environment?

I haven't thought of this explanation because BufFileWrite() only copies the
data to a buffer in the BufFile structure and BufFileDumpBuffer() writes the
buffer. Maybe valgrind is able to track the copying?

--
Antonin Houska
Web: https://www.cybertec-postgresql.com