[PATCH] Add pg_current_vxact_id() function to expose virtual transaction IDs

[Pavlo Golub]

Hi hackers,


current backend's virtual transaction ID (VXID).


or parse log files to obtain this information.


PostgreSQL for consistency.

Use cases:
1. Application transaction tracking and correlation with logs
2. Monitoring read-only transactions (which never get regular XIDs)
3. Debugging transaction behavior without querying pg_locks
4. Building monitoring tools that need consistent transaction identity

The function follows the same pattern as pg_current_xact_id() and
pg_current_xact_id_if_assigned(), providing a clean API for a commonly
needed piece of information.

Changes:

- OID 5101 (verified available with unused_oids script)
- Comprehensive regression tests in xid.sql
- Documentation in func-info.sgml and xact.sgml




Best regards,
Pavlo Golub

I'd like to propose a new function pg_current_vxact_id() that returns the Virtual transaction IDs are fundamental to PostgreSQL's transaction tracking, appearing in pg_locks.virtualtransaction, log output via %v placeholder, and internal transaction management. However, there's currently no direct SQL function to retrieve the current VXID, forcing applications to query pg_locks The patch adds pg_current_vxact_id() which returns the VXID as text in the format "procNumber/lxid" (e.g., "3/42"), matching the format used throughout - Added function in xid8funcs.c (alongside related transaction ID functions) - Format kept in sync with existing VXID representations in elog.c and lockfuncs.c The v1 patch is attached. Tests pass cleanly with "meson test regress/regress".

v1-0001-add-pg_current_vxact_id-function.patch
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