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>, a.kondratov@postgrespro.ru
Cc: Tomas Vondra <tomas.vondra@2ndquadrant.com>, Peter Eisentraut <peter.eisentraut@2ndquadrant.com>, PostgreSQL Hackers <pgsql-hackers@postgresql.org>
Date: 2019-10-22T05:16:35Z
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 Thu, Oct 3, 2019 at 1:18 PM Dilip Kumar <dilipbalaut@gmail.com> wrote:
>
> I have attempted to test the performance of (Stream + Spill) vs
> (Stream + BGW pool) and I can see the similar gain what Alexey had
> shown[1].
>
> In addition to this, I have rebased the latest patchset [2] without
> the two-phase logical decoding patch set.
>
> Test results:
> I have repeated the same test as Alexy[1] for 1kk and 1kk data and
> here is my result
> Stream + Spill
> N           time on master(sec)   Total xact time (sec)
> 1kk               6                               21
> 3kk             18                               55
>
> Stream + BGW pool
> N          time on master(sec)  Total xact time (sec)
> 1kk              6                              13
> 3kk            19                              35
>

I think the test results for the master are missing.  Also, how about
running these tests over a network (means master and subscriber are
not on the same machine)?   In general, yours and Alexy's test results
show that there is merit by having workers applying such transactions.
  OTOH, as noted above [1], we are also worried about the performance
of Rollbacks if we follow that approach.  I am not sure how much we
need to worry about Rollabcks if commits are faster, but can we think
of recording the changes in memory and only write to a file if the
changes are above a certain threshold?  I think that might help saving
I/O in many cases.  I am not very sure if we do that how much
additional workers can help, but they might still help.  I think we
need to do some tests and experiments to figure out what is the best
approach?  What do you think?

Tomas, Alexey, do you have any thoughts on this matter?  I think it is
important that we figure out the way to proceed in this patch.

[1] - https://www.postgresql.org/message-id/b25ce80e-f536-78c8-d5c8-a5df3e230785%40postgrespro.ru

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