Re: When UPDATE a row in a table with BEFORE ROW UPDATE trigger, the XMAX of new tuple is set to current XID - Mailing list pgsql-general

On Fri, 2025-08-08 at 09:20 +0800, Charles Qi wrote:
> Let me clarify the question, when the BEFORE ROW UPDATE trigger is presented
> Q. Why do we need to set the XMAX of the new tuple to the current xid?

Because the row gets locked, I'd say (without looking at your example).

> which risks piling up multixacts quickly in savepoint/exception block
> scenarios.

Why is that a problem for you?

Perhaps the trigger could use SELECT ... FOR ... to lock the row in the
strongest level your transaction needs.  A multixact is only necessary
if a subtransaction needs to take a stronger lock on the row than what
was there before.

Yours,
Laurenz Albe