Contents
txid_current_if_assigned()
A function returning the current transaction ID, if assigned
This entry relates to a PostgreSQL feature which is deprecated and may be desupported in future releases.
txid_current_if_assigned() is a system function returning the current transaction ID, if one is assigned.
txid_current_if_assigned() was added in PostgreSQL 8.3.
Usage
txid_current_if_assigned () → bigint
txid_current_if_assigned() returns the current transaction ID as a bigint. Note that a new transaction ID will be not be assigned until a non-read query is made in the current transaction.
This function is deprecated following the introduction of the xid8 data type in PostgreSQL 13 and is superseded by pg_current_xact_id_if_assigned().
Change history
- PostgreSQL 13
- marked as deprecated (commit 4c04be9b)
- PostgreSQL 8.3
- added (commit 1f92630f)
Examples
Basic usage example for txid_current_if_assigned() - a transaction will not have a transaction ID until it makes a change to the database:
postgres=# BEGIN;
BEGIN
postgres=*# SELECT txid_current_if_assigned();
txid_current_if_assigned
--------------------------
(1 row)
postgres=*# SELECT 1;
?column?
----------
1
(1 row)
postgres=*# SELECT txid_current_if_assigned();
txid_current_if_assigned
--------------------------
(1 row)
Time: 0.986 ms
postgres=*# INSERT INTO foo VALUES (1);
INSERT 0 1
postgres=*# SELECT txid_current_if_assigned();
txid_current_if_assigned
--------------------------
742
(1 row)
References
- PostgreSQL documentation: Deprecated Transaction ID and Snapshot Information Functions
