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

Konstantin Knizhnik <k.knizhnik@postgrespro.ru>

From: Konstantin Knizhnik <k.knizhnik@postgrespro.ru>

To: Tomas Vondra <tomas.vondra@2ndquadrant.com>, Alexey Kondratov <a.kondratov@postgrespro.ru>

Cc: Peter Eisentraut <peter.eisentraut@2ndquadrant.com>, Erik Rijkers <er@xs4all.nl>, Masahiko Sawada <sawada.mshk@gmail.com>, PostgreSQL Hackers <pgsql-hackers@postgresql.org>

Date: 2019-08-30T15:59:32Z

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 →

Tighten the concurrent abort check during decoding.
- 2ce353fc1902 14.0 landed
Improve hash_create()'s API for some added robustness.
- b3817f5f7746 14.0 landed
Use HASH_BLOBS for xidhash.
- a1b8aa1e4eec 14.0 landed
Fix initialization of RelationSyncEntry for streaming transactions.
- 69bd60672af6 14.0 landed
Remove unused function declaration in logicalproto.h.
- ddd5f6d2609b 14.0 landed
Add additional tests to test streaming of in-progress transactions.
- 58b5ae9d62bd 14.0 landed
Fix inline marking introduced in commit 464824323e.
- ac15b499f7f9 14.0 landed
Add support for streaming to built-in logical replication.
- 464824323e57 14.0 landed
Fix the SharedFileSetUnregister API.
- 4ab77697f67a 14.0 landed
Fix comment in procarray.c
- 77c7267c37f7 14.0 cited
Suppress compiler warning in non-cassert builds.
- e942af7b8261 14.0 cited
Extend the BufFile interface.
- 808e13b282ef 14.0 landed
Mark a few logical decoding related variables with PGDLLIMPORT.
- b48cac3b10a0 14.0 landed
Implement streaming mode in ReorderBuffer.
- 7259736a6e5b 14.0 landed
Extend the logical decoding output plugin API with stream methods.
- 45fdc9738b36 14.0 landed
WAL Log invalidations at command end with wal_level=logical.
- c55040ccd017 14.0 landed
Immediately WAL-log subtransaction and top-level XID association.
- 0bead9af484c 14.0 landed
Allow logical replication to transfer data in binary format.
- 9de77b545313 14.0 cited
Only superuser can set sslcert/sslkey in postgres_fdw user mappings
- cebf9d6e6ee1 13.0 cited
Track statistics for spilling of changes from ReorderBuffer.
- 9290ad198b15 13.0 landed
Add logical_decoding_work_mem to limit ReorderBuffer memory usage.
- cec2edfa7859 13.0 landed
logical decoding: process ASSIGNMENT during snapshot build
- bac2fae05c77 13.0 cited
Emit invalidations to standby for transactions without xid.
- c6ff84b06a68 9.6.0 cited

>
> FWIW my understanding is that the speedup comes mostly from 
> elimination of
> the serialization to a file. That however requires savepoints to handle
> aborts of subtransactions - I'm pretty sure I'd be trivial to create a
> workload where this will be much slower (with many aborts of large
> subtransactions).
>
>

I think that instead of defining savepoints it is simpler and more 
efficient to use

BeginInternalSubTransaction + 
ReleaseCurrentSubTransaction/RollbackAndReleaseCurrentSubTransaction

as it is done in PL/pgSQL (pl_exec.c).
Not sure if it can pr

-- 
Konstantin Knizhnik
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company