Implement WAIT FOR command WAIT FOR is to be used on standby and specifies waiting for the specific WAL location to be replayed. This option is useful when the user makes some data changes on primary and needs a guarantee to see these changes are on standby.
WAIT FOR needs to wait without any snapshot held. Otherwise, the snapshot could prevent the replay of WAL records, implying a kind of self-deadlock. This is why separate utility command seems appears to be the most robust way to implement this functionality. It's not possible to implement this as a function. Previous experience shows that stored procedures also have limitation in this aspect. Discussion: https://www.postgresql.org/message-id/flat/capphfdsjtzlvzxjgt8rjhcybm0d5dwko+bbjcirozj6nybo...@mail.gmail.com Discussion: https://www.postgresql.org/message-id/flat/CABPTF7UNft368x-RgOXkfj475OwEbp%2BVVO-wEXz7StgjD_%3D6sw%40mail.gmail.com Author: Kartyshov Ivan <[email protected]> Author: Alexander Korotkov <[email protected]> Author: Xuneng Zhou <[email protected]> Reviewed-by: Michael Paquier <[email protected]> Reviewed-by: Peter Eisentraut <[email protected]> Reviewed-by: Dilip Kumar <[email protected]> Reviewed-by: Amit Kapila <[email protected]> Reviewed-by: Alexander Lakhin <[email protected]> Reviewed-by: Bharath Rupireddy <[email protected]> Reviewed-by: Euler Taveira <[email protected]> Reviewed-by: Heikki Linnakangas <[email protected]> Reviewed-by: Kyotaro Horiguchi <[email protected]> Reviewed-by: jian he <[email protected]> Reviewed-by: Álvaro Herrera <[email protected]> Reviewed-by: Xuneng Zhou <[email protected]> Branch ------ master Details ------- https://git.postgresql.org/pg/commitdiff/447aae13b0305780e87cac7b0dd669db6fab3d9d Modified Files -------------- doc/src/sgml/high-availability.sgml | 54 ++++++ doc/src/sgml/ref/allfiles.sgml | 1 + doc/src/sgml/ref/wait_for.sgml | 234 +++++++++++++++++++++++ doc/src/sgml/reference.sgml | 1 + src/backend/access/transam/xact.c | 6 + src/backend/access/transam/xlog.c | 7 + src/backend/access/transam/xlogrecovery.c | 11 ++ src/backend/commands/Makefile | 3 +- src/backend/commands/meson.build | 1 + src/backend/commands/wait.c | 212 +++++++++++++++++++++ src/backend/parser/gram.y | 33 +++- src/backend/storage/lmgr/proc.c | 6 + src/backend/tcop/pquery.c | 12 +- src/backend/tcop/utility.c | 22 +++ src/include/commands/wait.h | 22 +++ src/include/nodes/parsenodes.h | 8 + src/include/parser/kwlist.h | 2 + src/include/tcop/cmdtaglist.h | 1 + src/test/recovery/meson.build | 3 +- src/test/recovery/t/049_wait_for_lsn.pl | 302 ++++++++++++++++++++++++++++++ src/tools/pgindent/typedefs.list | 1 + 21 files changed, 931 insertions(+), 11 deletions(-)
