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2025-11-15Fix incorrect function name in commentsAlexander Korotkov
Update comments to reference WaitForLSN() instead of the outdated WaitForLSNReplay() function name. Discussion: https://postgr.es/m/CABPTF7UieOYbOgH3EnQCasaqcT1T4N6V2wammwrWCohQTnD_Lw%40mail.gmail.com Author: Xuneng Zhou <xunengzhou@gmail.com> Reviewed-by: Alexander Korotkov <aekorotkov@gmail.com>
2025-11-05Implement WAIT FOR commandAlexander Korotkov
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+BBjcirozJ6nYbOW8Q@mail.gmail.com Discussion: https://www.postgresql.org/message-id/flat/CABPTF7UNft368x-RgOXkfj475OwEbp%2BVVO-wEXz7StgjD_%3D6sw%40mail.gmail.com Author: Kartyshov Ivan <i.kartyshov@postgrespro.ru> Author: Alexander Korotkov <aekorotkov@gmail.com> Author: Xuneng Zhou <xunengzhou@gmail.com> Reviewed-by: Michael Paquier <michael@paquier.xyz> Reviewed-by: Peter Eisentraut <peter.eisentraut@enterprisedb.com> Reviewed-by: Dilip Kumar <dilipbalaut@gmail.com> Reviewed-by: Amit Kapila <amit.kapila16@gmail.com> Reviewed-by: Alexander Lakhin <exclusion@gmail.com> Reviewed-by: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com> Reviewed-by: Euler Taveira <euler@eulerto.com> Reviewed-by: Heikki Linnakangas <hlinnaka@iki.fi> Reviewed-by: Kyotaro Horiguchi <horikyota.ntt@gmail.com> Reviewed-by: jian he <jian.universality@gmail.com> Reviewed-by: Álvaro Herrera <alvherre@kurilemu.de> Reviewed-by: Xuneng Zhou <xunengzhou@gmail.com>
2020-04-08Revert 0f5ca02f53Alexander Korotkov
0f5ca02f53 introduces 3 new keywords. It appears to be too much for relatively small feature. Given now we past feature freeze, it's already late for discussion of the new syntax. So, revert. Discussion: https://postgr.es/m/28209.1586294824%40sss.pgh.pa.us
2020-04-07Implement waiting for given lsn at transaction startAlexander Korotkov
This commit adds following optional clause to BEGIN and START TRANSACTION commands. WAIT FOR LSN lsn [ TIMEOUT timeout ] New clause pospones transaction start till given lsn is applied on standby. This clause allows user be sure, that changes previously made on primary would be visible on standby. New shared memory struct is used to track awaited lsn per backend. Recovery process wakes up backend once required lsn is applied. Author: Ivan Kartyshov, Anna Akenteva Reviewed-by: Craig Ringer, Thomas Munro, Robert Haas, Kyotaro Horiguchi Reviewed-by: Masahiko Sawada, Ants Aasma, Dmitry Ivanov, Simon Riggs Reviewed-by: Amit Kapila, Alexander Korotkov Discussion: https://postgr.es/m/0240c26c-9f84-30ea-fca9-93ab2df5f305%40postgrespro.ru