Horton

Re: [HACKERS] make async slave to wait for lsn to be replayed

Ivan Kartyshov <i.kartyshov@postgrespro.ru>

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From: Kartyshov Ivan <i.kartyshov@postgrespro.ru>
To: Alexander Korotkov <aekorotkov@gmail.com>
Cc: pgsql-hackers@lists.postgresql.org
Date: 2023-12-08T09:46:55Z
Lists: pgsql-hackers

Attachments

Should rise disscusion on separate utility statement or find
case where procedure version is failed.

1) Classic (wait_classic_v3.patch)
https://www.postgresql.org/message-id/3cc883048264c2e9af022033925ff8db%40postgrespro.ru
==========
advantages: multiple wait events, separate WAIT FOR statement
disadvantages: new words in grammar



WAIT FOR  [ANY | ALL] event [, ...]
BEGIN [ WORK | TRANSACTION ] [ transaction_mode [, ...] ]
     [ WAIT FOR [ANY | ALL] event [, ...]]
event:
LSN value
TIMEOUT number_of_milliseconds
timestamp



2) After style: Kyotaro and Freund (wait_after_within_v2.patch)
https://www.postgresql.org/message-id/d3ff2e363af60b345f82396992595a03%40postgrespro.ru
==========
advantages: no new words in grammar
disadvantages: a little harder to understand



AFTER lsn_event [ WITHIN delay_milliseconds ] [, ...]
BEGIN [ WORK | TRANSACTION ] [ transaction_mode [, ...] ]
     [ AFTER lsn_event [ WITHIN delay_milliseconds ]]
START [ WORK | TRANSACTION ] [ transaction_mode [, ...] ]
     [ AFTER lsn_event [ WITHIN delay_milliseconds ]]



3) Procedure style: Tom Lane and Kyotaro (wait_proc_v7.patch)
https://www.postgresql.org/message-id/27171.1586439221%40sss.pgh.pa.us
https://www.postgresql.org/message-id/20210121.173009.235021120161403875.horikyota.ntt%40gmail.com
==========
advantages: no new words in grammar,like it made in
pg_last_wal_replay_lsn
disadvantages: use snapshot xmin trick
SELECT pg_waitlsn(‘LSN’, timeout);
SELECT pg_waitlsn_infinite(‘LSN’);
SELECT pg_waitlsn_no_wait(‘LSN’);


Regards
-- 
Ivan Kartyshov
Postgres Professional: www.postgrespro.com

Commits

  1. Ensure standby promotion point in 043_wal_replay_wait.pl

  2. Minor cleanup related to pg_wal_replay_wait() procedure

  3. Adjust pg_wal_replay_wait() procedure behavior on promoted standby

  4. pg_wal_replay_wait(): Fix typo in the doc

  5. Implement pg_wal_replay_wait() stored procedure

  6. Revert: Implement pg_wal_replay_wait() stored procedure

  7. Call WaitLSNCleanup() in AbortTransaction()

  8. Clarify what is protected by WaitLSNLock

  9. Use an LWLock instead of a spinlock in waitlsn.c

  10. Use the pairing heap instead of a flat array for LSN replay waiters

  11. Minor improvements for waitlsn.c

  12. Make the order of the header file includes consistent