How do I find out the numeric ID of the current Postgres Transaction?

"System Information Functions", "Transaction IDs and Snapshots".

You can get the transaction id from:

txid_current()

You can additionally get the in-progress transactions in the snaption it's seeing from:

txid_snapshot_xip(txid_current_snapshot())

A few more functions are detailed in the manual:

http://www.postgresql.org/docs/current/static/functions-info.html#FUNCTIONS-TXID-SNAPSHOT

Postgres has added txid_current_if_assigned() in version 10.

Related