Horton

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

Ajin Cherian <itsajin@gmail.com>

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From: Ajin Cherian <itsajin@gmail.com>
To: Amit Kapila <amit.kapila16@gmail.com>
Cc: Dilip Kumar <dilipbalaut@gmail.com>, 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: 2020-07-09T02:48:17Z
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, Jul 9, 2020 at 12:28 PM Amit Kapila <amit.kapila16@gmail.com> wrote:

> On Wed, Jul 8, 2020 at 7:31 PM Ajin Cherian <itsajin@gmail.com> wrote:
>
> Thanks for showing the interest in patch.  How have you ensured that
> streaming is happening?  I don't think the proposed patch can ensure
> it for every case because we also rely on logical_decoding_work_mem to
> decide whether to stream/spill, see ReorderBufferCheckMemoryLimit.  I
> think with your patch it will allow streaming for cases where we have
> large amount of WAL to decode.
>
>
Maybe I missed something but I looked at ReorderBufferCheckMemoryLimit,
even there it checks the same function ReorderBufferCanStream () and
decides whether to stream or spill. Did I miss something?

    while (rb->size >= logical_decoding_work_mem * 1024L)
    {
        /*
         * Pick the largest transaction (or subtransaction) and evict it from
         * memory by streaming, if supported. Otherwise, spill to disk.
         */
        if (ReorderBufferCanStream(rb) &&
            (txn = ReorderBufferLargestTopTXN(rb)) != NULL)
        {
            /* we know there has to be one, because the size is not zero */
            Assert(txn && !txn->toptxn);
            Assert(txn->total_size > 0);
            Assert(rb->size >= txn->total_size);

            ReorderBufferStreamTXN(rb, txn);
        }
        else
        {

I will also add debug and test as you suggested.

regards,
Ajin Cherian
Fujitsu Australia