pgsql: Fix handling of errors in libpq pipelines - Mailing list pgsql-committers

From Alvaro Herrera
Subject pgsql: Fix handling of errors in libpq pipelines
Date
Msg-id E1rATqH-008hbj-MG@gemulon.postgresql.org
Whole thread Raw
List pgsql-committers
Fix handling of errors in libpq pipelines

The logic to keep the libpq command queue in sync with queries that have
been processed had a bug when errors were returned for reasons other
than problems in queries -- for example, when a connection is lost.  We
incorrectly consumed an element from the command queue every time, but
this is wrong and can lead to the queue becoming empty ahead of time,
leading to later malfunction: PQgetResult would return nothing,
potentially causing the calling application to enter a busy loop.

Fix by making the SYNC queue element a barrier that can only be consumed
when a SYNC message is received.

Backpatch to 14.

Reported by: Иван Трофимов (Ivan Trofimov) <i.trofimow@yandex.ru>
Discussion: https://postgr.es/m/17948-fcace7557e449957@postgresql.org

Branch
------
REL_15_STABLE

Details
-------
https://git.postgresql.org/pg/commitdiff/1171c6e7418564296e9023859f68225b247427a7

Modified Files
--------------
src/interfaces/libpq/fe-exec.c      | 61 ++++++++++++++++++++++++-------------
src/interfaces/libpq/fe-protocol3.c |  9 ++----
src/interfaces/libpq/libpq-int.h    |  3 +-
3 files changed, 44 insertions(+), 29 deletions(-)


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