Allow logical decoding on standbys Unsurprisingly, this requires wal_level = logical to be set on the primary and standby. The infrastructure added in 26669757b6a ensures that slots are invalidated if the primary's wal_level is lowered.
Creating a slot on a standby waits for a xl_running_xact record to be processed. If the primary is idle (and thus not emitting xl_running_xact records), that can take a while. To make that faster, this commit also introduces the pg_log_standby_snapshot() function. By executing it on the primary, completion of slot creation on the standby can be accelerated. Note that logical decoding on a standby does not itself enforce that required catalog rows are not removed. The user has to use physical replication slots + hot_standby_feedback or other measures to prevent that. If catalog rows required for a slot are removed, the slot is invalidated. See 6af1793954e for an overall design of logical decoding on a standby. Bumps catversion, for the addition of the pg_log_standby_snapshot() function. Author: "Drouvot, Bertrand" <bertranddrouvot...@gmail.com> Author: Andres Freund <and...@anarazel.de> (in an older version) Author: Amit Khandekar <amitdkhan...@gmail.com> (in an older version) Reviewed-by: Andres Freund <and...@anarazel.de> Reviewed-by: FabrÌzio de Royes Mello <fabriziome...@gmail.com> Reviewed-by: Amit Kapila <amit.kapil...@gmail.com> Reviewed-By: Robert Haas <robertmh...@gmail.com> Branch ------ master Details ------- https://git.postgresql.org/pg/commitdiff/0fdab27ad68a059a1663fa5ce48d76333f1bd74c Modified Files -------------- doc/src/sgml/func.sgml | 15 ++++++++ doc/src/sgml/logicaldecoding.sgml | 27 +++++++++++++++ src/backend/access/transam/xlog.c | 11 ++++++ src/backend/access/transam/xlogfuncs.c | 31 +++++++++++++++++ src/backend/catalog/system_functions.sql | 2 ++ src/backend/replication/logical/decode.c | 30 +++++++++++++++- src/backend/replication/logical/logical.c | 36 ++++++++++--------- src/backend/replication/slot.c | 57 ++++++++++++++++--------------- src/backend/replication/walsender.c | 48 +++++++++++++++++--------- src/include/access/xlog.h | 1 + src/include/catalog/catversion.h | 2 +- src/include/catalog/pg_proc.dat | 3 ++ 12 files changed, 202 insertions(+), 61 deletions(-)
