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pg_stat_get_backend_idset()
pg_stat_get_backend_idset() is a system function which generates a list of sequential IDs for each current backend, which can then be provided to a of functions, each of which returns a specifc items of information about each backend. These functions underly the pg_stat_activity view, but can be used to extract a subset of information provided by that view.
pg_stat_get_backend_idset() was added in PostgreSQL 7.2.
Usage
pg_stat_get_backend_idset () → setof integer
In PostgreSQL 16 and later, the integers returned are the actual backend IDs.
In PostgreSQL 15 and earlier, the integers returned from 1 to the number of currently active backends.
Change history
- PostgreSQL 16
- returns actual backend IDs (commit d7e39d72)
- PostgreSQL 7.2
- added (commit 140ddb78)
Examples
Basic usage example for pg_stat_get_backend_idset() in PostgreSQL 15 and earlier:
postgres=# SELECT * FROM pg_stat_get_backend_idset();
pg_stat_get_backend_idset
---------------------------
1
2
3
4
5
6
(6 rows)
In PostgreSQL 16 and later:
postgres=# SELECT * FROM pg_stat_get_backend_idset();
pg_stat_get_backend_idset
---------------------------
1
2
3
256
258
259
(6 rows)
By itself this information is of little use; normally this query will be combined with one or more of the per-backend statistics functions:
postgres=# SELECT pg_stat_get_backend_pid(s.id) AS pid FROM (SELECT pg_stat_get_backend_idset() AS id) AS s; pid ------- 18206 18207 18217 18203 18202 18205 (6 rows)
References
- PostgreSQL documentation: Per-Backend Statistics Functions