postgres_fdw: Inherit the local transaction's access/deferrable modes. Previously, postgres_fdw always 1) opened a remote transaction in READ WRITE mode even when the local transaction was READ ONLY, causing a READ ONLY transaction using it that references a foreign table mapped to a remote view executing a volatile function to write in the remote side, and 2) opened the remote transaction in NOT DEFERRABLE mode even when the local transaction was DEFERRABLE, causing a SERIALIZABLE READ ONLY DEFERRABLE transaction using it to abort due to a serialization failure in the remote side.
To avoid these, modify postgres_fdw to open a remote transaction in the same access/deferrable modes as the local transaction. This commit also modifies it to open a remote subtransaction in the same access mode as the local subtransaction. Although these issues exist since the introduction of postgres_fdw, there have been no reports from the field. So it seems fine to just fix them in master only. Author: Etsuro Fujita <etsuro.fuj...@gmail.com> Reviewed-by: Ashutosh Bapat <ashutosh.bapat....@gmail.com> Reviewed-by: Tom Lane <t...@sss.pgh.pa.us> Discussion: https://postgr.es/m/CAPmGK16n_hcUUWuOdmeUS%2Bw4Q6dZvTEDHb%3DOP%3D5JBzo-M3QmpQ%40mail.gmail.com Branch ------ master Details ------- https://git.postgresql.org/pg/commitdiff/e5a3c9d9b5ce535151d3a7e3173e8d27d2d8cd58 Modified Files -------------- contrib/postgres_fdw/connection.c | 99 ++++++++++++++++-- contrib/postgres_fdw/expected/postgres_fdw.out | 134 +++++++++++++++++++++++++ contrib/postgres_fdw/sql/postgres_fdw.sql | 78 ++++++++++++++ doc/src/sgml/postgres-fdw.sgml | 15 +++ src/backend/access/transam/xact.c | 28 ++++++ src/include/access/xact.h | 1 + 6 files changed, 347 insertions(+), 8 deletions(-)
