Horton

Re: ERROR: subtransaction logged without previous top-level txn record

Amit Kapila <amit.kapila16@gmail.com>

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From: Amit Kapila <amit.kapila16@gmail.com>
To: Arseny Sher <a.sher@postgrespro.ru>
Cc: Andres Freund <andres@anarazel.de>, "Hsu, John" <hsuchen@amazon.com>, "pgsql-bugs@lists.postgresql.org" <pgsql-bugs@lists.postgresql.org>
Date: 2020-03-02T06:26:33Z
Lists: pgsql-bugs, pgsql-hackers 
On Sun, Feb 9, 2020 at 9:37 PM Arseny Sher <a.sher@postgrespro.ru> wrote:
>
>
> Somehow I hadn't realized this earlier, so my comments/commit messages
> in patches above were not accurate here; I've edited them. Also in the
> first patch serialized snapshots are not no longer used for new slot
> creation at all, as Andres suggested above.
>

+ /*
+ * Don't use serialized snapshot if we are not sure where all
+ * currently running xacts will finish (new slot creation).
+ * (Actually, if we came here through xl_running_xacts, we could perform
+ * SNAPBUILD_FULL_SNAPSHOT -> SNAPBUILD_CONSISTENT transition properly,
+ * but added lines of code would hardly worth the benefit.)
+ */
+ if (builder->start_decoding_at == InvalidXLogRecPtr)
+ return false;

Instead of using start_decoding_at to decide whether to restore
snapshot or not, won't it be better to have new variable in SnapBuild
(say can_use_serialized_snap or something like that) and for this
purpose?

I think the patch is trying to use a variable that is not meant for
the purpose we are using for it, so not sure if it is the right
direction for the fix.

-- 
With Regards,
Amit Kapila.
EnterpriseDB: http://www.enterprisedb.com

Commits

  1. Stop demanding that top xact must be seen before subxact in decoding.

  2. logical decoding: process ASSIGNMENT during snapshot build

  3. Fix operator naming in pg_trgm GUC option descriptions