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3c5db1d6b0
pg_wal_replay_wait() 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. The queue of waiters is stored in the shared memory as an LSN-ordered pairing heap, where the waiter with the nearest LSN stays on the top. During the replay of WAL, waiters whose LSNs have already been replayed are deleted from the shared memory pairing heap and woken up by setting their latches. pg_wal_replay_wait() 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 it is only possible to implement pg_wal_replay_wait() as a procedure working without an active snapshot, not a function. Catversion is bumped. Discussion: https://postgr.es/m/eb12f9b03851bb2583adab5df9579b4b%40postgrespro.ru Author: Kartyshov Ivan, Alexander Korotkov Reviewed-by: Michael Paquier, Peter Eisentraut, Dilip Kumar, Amit Kapila Reviewed-by: Alexander Lakhin, Bharath Rupireddy, Euler Taveira Reviewed-by: Heikki Linnakangas, Kyotaro Horiguchi
63 lines
2.8 KiB
C
63 lines
2.8 KiB
C
/*-------------------------------------------------------------------------
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*
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* catversion.h
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* "Catalog version number" for PostgreSQL.
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*
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* The catalog version number is used to flag incompatible changes in
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* the PostgreSQL system catalogs. Whenever anyone changes the format of
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* a system catalog relation, or adds, deletes, or modifies standard
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* catalog entries in such a way that an updated backend wouldn't work
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* with an old database (or vice versa), the catalog version number
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* should be changed. The version number stored in pg_control by initdb
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* is checked against the version number compiled into the backend at
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* startup time, so that a backend can refuse to run in an incompatible
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* database.
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*
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* The point of this feature is to provide a finer grain of compatibility
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* checking than is possible from looking at the major version number
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* stored in PG_VERSION. It shouldn't matter to end users, but during
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* development cycles we usually make quite a few incompatible changes
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* to the contents of the system catalogs, and we don't want to bump the
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* major version number for each one. What we can do instead is bump
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* this internal version number. This should save some grief for
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* developers who might otherwise waste time tracking down "bugs" that
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* are really just code-vs-database incompatibilities.
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*
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* The rule for developers is: if you commit a change that requires
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* an initdb, you should update the catalog version number (as well as
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* notifying the pgsql-hackers mailing list, which has been the
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* informal practice for a long time).
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*
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* The catalog version number is placed here since modifying files in
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* include/catalog is the most common kind of initdb-forcing change.
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* But it could be used to protect any kind of incompatible change in
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* database contents or layout, such as altering tuple headers.
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* Another common reason for a catversion update is a change in parsetree
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* external representation, since serialized parsetrees appear in stored
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* rules and new-style SQL functions. Almost any change in primnodes.h or
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* parsenodes.h will warrant a catversion update.
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*
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*
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* Portions Copyright (c) 1996-2024, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* src/include/catalog/catversion.h
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*
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*-------------------------------------------------------------------------
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*/
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#ifndef CATVERSION_H
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#define CATVERSION_H
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/*
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* We could use anything we wanted for version numbers, but I recommend
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* following the "YYYYMMDDN" style often used for DNS zone serial numbers.
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* YYYYMMDD are the date of the change, and N is the number of the change
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* on that day. (Hopefully we'll never commit ten independent sets of
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* catalog changes on the same day...)
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*/
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/* yyyymmddN */
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#define CATALOG_VERSION_NO 202408021
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#endif
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