Re: Trigger Behavior in Transactions

Joshua Kramer wrote:
>
> Greetings,
>
> Where in the documentation can I find information on the low-level
> behavior of triggers that fire as a result of insert/update statements
> inside of transactions?
>
> Do the triggers fire at the point the transaction is COMMITted? Or as
> soon as the statements are encountered? (If this is the case, how are
> rollbacks done - does the trigger also fire for the rollback?)
>
> I am creating a mechanism for updating PG databases remotely (from another
> PG database) for a magazine article I'm writing, and I need to figure out
> how to engineer the trigger mechamisms so they work properly.

These are complex questions. Triggers fire at the end of the statement,
unless they are DEFERRRED (look that up). I recommend you look up MVCC
to see how triggers fired on statement end are automatically rolled back
on abort, meaning we don't re-run the triggers on abort, the changes
the trigger made are ignored by other backends.

--
Bruce Momjian | http://candle.pha.pa.us
pgman(at)candle(dot)pha(dot)pa(dot)us | (610) 359-1001
+ If your life is a hard drive, | 13 Roberts Road
+ Christ can be your backup. | Newtown Square, Pennsylvania 19073