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: Dilip Kumar <dilipbalaut@gmail.com>
Cc: Amit Kapila <amit.kapila16@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: 2020-07-10T05:31:19Z
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 Fri, Jul 10, 2020 at 3:11 PM Dilip Kumar <dilipbalaut@gmail.com> wrote:

> With your changes sometimes due to incomplete toast
> changes, if it can not pick the largest top txn for streaming it will
> hang forever in the while loop, in that case, it should go for
> spilling.
>
> 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)
>
>
>
Which is this condition (of not picking largest top txn)?
Wouldn't ReorderBufferLargestTopTXN then return a NULL? If not, is there a
way to know that a transaction cannot be streamed, so there can be an exit
condition for the while loop?

regards,
Ajin Cherian
Fujitsu Australia