Horton

Re: [HACKERS] logical decoding of two-phase transactions

Ajin Cherian <itsajin@gmail.com>

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From: Ajin Cherian <itsajin@gmail.com>
To: Amit Kapila <amit.kapila16@gmail.com>
Cc: Peter Smith <smithpb2250@gmail.com>, PostgreSQL Hackers <pgsql-hackers@postgresql.org>
Date: 2021-03-20T01:37:22Z
Lists: pgsql-hackers 
On Sat, Mar 20, 2021 at 1:35 AM Amit Kapila <amit.kapila16@gmail.com> wrote:

> On Fri, Mar 19, 2021 at 5:03 AM Ajin Cherian <itsajin@gmail.com> wrote:
> >
> > Missed the patch - 0001, resending.
> >
>
>
> @@ -538,10 +550,21 @@ CreateDecodingContext(XLogRecPtr start_lsn,
> ..
> + /* Set two_phase_at LSN only if it hasn't already been set. */
> + if (ctx->twophase && !MyReplicationSlot->data.two_phase_at)
> + {
> + MyReplicationSlot->data.two_phase_at = start_lsn;
> + slot->data.two_phase = true;
> + ReplicationSlotMarkDirty();
> + ReplicationSlotSave();
> + SnapBuildSetTwoPhaseAt(ctx->snapshot_builder, start_lsn);
> + }
>
> What if the walsender or apply worker restarts after setting
> two_phase_at/two_phase here and updating the two_phase state in
> pg_subscription? Won't we need to set SnapBuildSetTwoPhaseAt after
> restart as well?
>

After a restart,   two_phase_at will be set by calling
AllocateSnapshotBuilder with two_phase_at

@@ -207,7 +207,7 @@ StartupDecodingContext(List *output_plugin_options,
  ctx->reorder = ReorderBufferAllocate();
  ctx->snapshot_builder =
  AllocateSnapshotBuilder(ctx->reorder, xmin_horizon, start_lsn,
- need_full_snapshot, slot->data.initial_consistent_point);
+ need_full_snapshot, slot->data.two_phase_at);

and then in  AllocateSnapshotBuilder:

@@ -309,7 +306,7 @@ AllocateSnapshotBuilder(ReorderBuffer *reorder,
  builder->initial_xmin_horizon = xmin_horizon;
  builder->start_decoding_at = start_lsn;
  builder->building_full_snapshot = need_full_snapshot;
- builder->initial_consistent_point = initial_consistent_point;
+ builder->two_phase_at = two_phase_at;

regards,
Ajin Cherian
Fujitsu Australia

Commits

  1. Add prepare API support for streaming transactions in logical replication.

  2. Doc: minor improvements for logical replication protocol documentation.

  3. Fix test failure in 021_twophase.pl.

  4. Refactor to make common functions in proto.c and worker.c.

  5. Unify PostgresNode's new() and get_new_node() methods

  6. Fix potential buffer overruns in proto.c.

  7. Add support for prepared transactions to built-in logical replication.

  8. Refactor function parse_subscription_options.

  9. Allow enabling two-phase option via replication protocol.

  10. Don't use Asserts to check for violations of replication protocol.

  11. Improve psql tab completion for options of subcriptions and publications

  12. Rearrange logrep worker's snapshot handling some more.

  13. doc: Update information of new messages for logical replication.

  14. ALTER SUBSCRIPTION ... ADD/DROP PUBLICATION

  15. Allow pgoutput to send logical decoding messages.

  16. Refactor function parse_output_parameters.

  17. Avoid repeated decoding of prepared transactions after a restart.

  18. Fix an oversight in ReorderBufferFinishPrepared.

  19. Allow multiple xacts during table sync in logical replication.

  20. Fix replication of in-progress transactions in tablesync worker.

  21. Fix 'skip-empty-xacts' option in test_decoding for streaming mode.

  22. Use Enum for top level logical replication message types.

  23. Add support for streaming to built-in logical replication.

  24. Fix the logical streaming test.

  25. Implement streaming mode in ReorderBuffer.

  26. Extend the logical decoding output plugin API with stream methods.

  27. Store 2PC GID in commit/abort WAL recs for logical decoding