|From:||Craig Ringer <craig(at)2ndquadrant(dot)com>|
|To:||PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org>|
|Subject:||[PATCH] Transaction traceability - txid_status(bigint)|
|Views:||Raw Message | Whole Thread | Download mbox|
Following on from
bigint txids vs 'xid' type, new txid_recent(bigint) => xid
here's a patch that implements a txid_status(bigint) function to report the
commit status of a function.
If an application is disconnected while a COMMIT request is in flight,
the backend crashes mid-commit, etc, then an application may not be
sure whether or not a commit completed successfully or was rolled
back. While two-phase commit solves this it does so at a considerable
overhead, so introduce a lighter alternative.
txid_status(bigint) lets an application determine the status of a
a commit based on an xid-with-epoch as returned by txid_current()
or similar. Status may be committed, aborted, in-progress (including
prepared xacts) or null if the xact is too old for its commit status
to still be retained because it has passed the wrap-around epoch
Applications must call txid_current() in their transactions to make
much use of this since PostgreSQL does not automatically report an xid
to the client when one is assigned.
A future protocol enhancement to report txid assignment would be very
useful, but quite separate to this.
Craig Ringer http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
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