Horton

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

Amit Kapila <akapila@postgresql.org>

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Commit: 0bead9af484c1d0a67e690fda47011addaa5bc9d
Author: Amit Kapila <akapila@postgresql.org>
Date: 2020-07-20T03:18:26Z
Releases: 14.0 
Immediately WAL-log subtransaction and top-level XID association.

The logical decoding infrastructure needs to know which top-level
transaction the subxact belongs to, in order to decode all the
changes. Until now that might be delayed until commit, due to the
caching (GPROC_MAX_CACHED_SUBXIDS), preventing features requiring
incremental decoding.

So we also write the assignment info into WAL immediately, as part
of the next WAL record (to minimize overhead) only when wal_level=logical.
We can not remove the existing XLOG_XACT_ASSIGNMENT WAL as that is
required for avoiding overflow in the hot standby snapshot.

Bump XLOG_PAGE_MAGIC, since this introduces XLR_BLOCK_ID_TOPLEVEL_XID.

Author: Tomas Vondra, Dilip Kumar, Amit Kapila
Reviewed-by: Amit Kapila
Tested-by: Neha Sharma and Mahendra Singh Thalor
Discussion: https://postgr.es/m/688b0b7f-2f6c-d827-c27b-216a8e3ea700@2ndquadrant.com

Files

PathChange+/−
src/backend/access/transam/xact.c modified +50 −0
src/backend/access/transam/xloginsert.c modified +21 −2
src/backend/access/transam/xlogreader.c modified +5 −0
src/backend/replication/logical/decode.c modified +23 −21
src/include/access/xact.h modified +3 −0
src/include/access/xlog.h modified +1 −0
src/include/access/xlog_internal.h modified +1 −1
src/include/access/xlogreader.h modified +3 −0
src/include/access/xlogrecord.h modified +1 −0

Discussion