Contents
pg_current_xact_id_if_assigned()
A function returning the current transaction ID, if assigned
pg_current_xact_id_if_assigned() is a system function returning the current transaction ID, if one is assigned.
pg_current_xact_id_if_assigned() was added in PostgreSQL 13.
Usage
pg_current_xact_id_if_assigned () → xid8
pg_current_xact_id_if_assigned() returns the current transaction ID as xid8. Note that a new transaction ID will be not be assigned until a non-read query is made in the current transaction.
pg_current_xact_id_if_assigned() replaces txid_current_if_assigned().
Change history
- PostgreSQL 13
- added (commit 4c04be9b)
Examples
Basic usage example for pg_current_xact_id_if_assigned() - a transaction will not have a transaction ID until it makes a change to the database:
postgres=# BEGIN;
BEGIN
postgres=*# SELECT pg_current_xact_id_if_assigned();
pg_current_xact_id_if_assigned
--------------------------------
(1 row)
postgres=*# SELECT 1;
?column?
----------
1
(1 row)
postgres=*# SELECT pg_current_xact_id_if_assigned();
pg_current_xact_id_if_assigned
--------------------------------
(1 row)
postgres=*# INSERT INTO foo VALUES (1);
INSERT 0 1
postgres=*# SELECT pg_current_xact_id_if_assigned();
pg_current_xact_id_if_assigned
--------------------------------
764
(1 row)
References
- PostgreSQL documentation: Transaction ID and Snapshot Information Functions
