Horton

Re: PATCH: logical_work_mem and logical streaming of large in-progress transactions

Amit Kapila <amit.kapila16@gmail.com>

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From: Amit Kapila <amit.kapila16@gmail.com>
To: Dilip Kumar <dilipbalaut@gmail.com>
Cc: Erik Rijkers <er@xs4all.nl>, Kuntal Ghosh <kuntalghosh.2007@gmail.com>, Tomas Vondra <tomas.vondra@2ndquadrant.com>, Michael Paquier <michael@paquier.xyz>, Peter Eisentraut <peter.eisentraut@2ndquadrant.com>, PostgreSQL Hackers <pgsql-hackers@postgresql.org>
Date: 2020-07-06T09:39:19Z
Lists: pgsql-hackers

Commits

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

  1. Tighten the concurrent abort check during decoding.

  2. Improve hash_create()'s API for some added robustness.

  3. Use HASH_BLOBS for xidhash.

  4. Fix initialization of RelationSyncEntry for streaming transactions.

  5. Remove unused function declaration in logicalproto.h.

  6. Add additional tests to test streaming of in-progress transactions.

  7. Fix inline marking introduced in commit 464824323e.

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

  9. Fix the SharedFileSetUnregister API.

  10. Fix comment in procarray.c

  11. Suppress compiler warning in non-cassert builds.

  12. Extend the BufFile interface.

  13. Mark a few logical decoding related variables with PGDLLIMPORT.

  14. Implement streaming mode in ReorderBuffer.

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

  16. WAL Log invalidations at command end with wal_level=logical.

  17. Immediately WAL-log subtransaction and top-level XID association.

  18. Allow logical replication to transfer data in binary format.

  19. Only superuser can set sslcert/sslkey in postgres_fdw user mappings

  20. Track statistics for spilling of changes from ReorderBuffer.

  21. Add logical_decoding_work_mem to limit ReorderBuffer memory usage.

  22. logical decoding: process ASSIGNMENT during snapshot build

  23. Emit invalidations to standby for transactions without xid.

On Mon, Jul 6, 2020 at 11:44 AM Dilip Kumar <dilipbalaut@gmail.com> wrote:
>
> On Mon, Jul 6, 2020 at 11:31 AM Amit Kapila <amit.kapila16@gmail.com> wrote:
> >
>
> > > > 10.  I have got the below failure once.  I have not investigated this
> > > > in detail as the patch is still under progress.  See, if you have any
> > > > idea?
> > > > #   Failed test 'check extra columns contain local defaults'
> > > > #   at t/013_stream_subxact_ddl_abort.pl line 81.
> > > > #          got: '2|0'
> > > > #     expected: '1000|500'
> > > > # Looks like you failed 1 test of 2.
> > > > make[2]: *** [check] Error 1
> > > > make[1]: *** [check-subscription-recurse] Error 2
> > > > make[1]: *** Waiting for unfinished jobs....
> > > > make: *** [check-world-src/test-recurse] Error 2
> > >
> > > Even I got the failure once and after that, it did not reproduce.  I
> > > have executed it multiple time but it did not reproduce again.  Are
> > > you able to reproduce it consistently?
> > >
> >
> > No, I am also not able to reproduce it consistently but I think this
> > can fail if a subscriber sends the replay_location before actually
> > replaying the changes.  First, I thought that extra send_feedback we
> > have in apply_handle_stream_commit might have caused this but I guess
> > that can't happen because we need the commit time location for that
> > and we are storing the same at the end of apply_handle_stream_commit
> > after applying all messages.  I am not sure what is going on here.  I
> > think we somehow need to reproduce this or some variant of this test
> > consistently to find the root cause.
>
> And I think it appeared first time for me,  so maybe either induced
> from past few versions so some changes in the last few versions might
> have exposed it.  I have noticed that almost 50% of the time I am able
> to reproduce after the clean build so I can trace back from which
> version it started appearing that way it will be easy to narrow down.
>

One more comment
ReorderBufferLargestTopTXN
{
..
dlist_foreach(iter, &rb->toplevel_by_lsn)
  {
  ReorderBufferTXN *txn;
+ Size size = 0;
+ Size largest_size = 0;

  txn = dlist_container(ReorderBufferTXN, node, iter.cur);

- /* if the current transaction is larger, remember it */
- if ((!largest) || (txn->size > largest->size))
+ /*
+ * If this transaction have some incomplete changes then only consider
+ * the size upto last complete lsn.
+ */
+ if (rbtxn_has_incomplete_tuple(txn))
+ size = txn->complete_size;
+ else
+ size = txn->total_size;
+
+ /* If the current transaction is larger then remember it. */
+ if ((largest != NULL || size > largest_size) && size > 0)

Here largest_size is a local variable inside the loop which is
initialized to 0 in each iteration and that will lead to picking each
next txn as largest.  This seems wrong to me.

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