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Re: Assertion failure in SnapBuildInitialSnapshot()

Amit Kapila <amit.kapila16@gmail.com>

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From: Amit Kapila <amit.kapila16@gmail.com>
To: Masahiko Sawada <sawada.mshk@gmail.com>
Cc: "Hayato Kuroda (Fujitsu)" <kuroda.hayato@fujitsu.com>, Andres Freund <andres@anarazel.de>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>, Thomas Munro <thomas.munro@gmail.com>
Date: 2023-01-31T06:55:53Z
Lists: pgsql-hackers 
On Tue, Jan 31, 2023 at 11:12 AM Masahiko Sawada <sawada.mshk@gmail.com> wrote:
>
> On Mon, Jan 30, 2023 at 9:41 PM Masahiko Sawada <sawada.mshk@gmail.com> wrote:
>
> I've attached patches for HEAD and backbranches. Please review them.
>

Shall we add a comment like the one below in
ReplicationSlotsComputeRequiredXmin()?
diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c
index f286918f69..e28d48bca7 100644
--- a/src/backend/replication/slot.c
+++ b/src/backend/replication/slot.c
@@ -840,6 +840,13 @@ ReplicationSlotsComputeRequiredXmin(bool already_locked)

        Assert(ReplicationSlotCtl != NULL);

+       /*
+        * It is possible that by the time we compute the agg_xmin
here and before
+        * updating replication_slot_xmin, the CreateInitDecodingContext() will
+        * compute and update replication_slot_xmin. So, we need to acquire
+        * ProcArrayLock here to avoid retreating the value of
replication_slot_xmin.
+        */
+

-- 
With Regards,
Amit Kapila.

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Fix a race condition in updating procArray->replication_slot_xmin.

  2. Don't retreat slot's confirmed_flush LSN.

  3. Add additional checks while creating the initial decoding snapshot.