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Home > Archive > PostgreSQL Discussion > December 2005 > Trigger Behavior in Transactions
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Trigger Behavior in Transactions
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| Joshua Kramer 2005-12-24, 1:23 pm |
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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.
Thanks,
-Josh
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| Bruce Momjian 2005-12-26, 11:23 am |
| 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@candle.pha.pa.us | (610) 359-1001
+ If your life is a hard drive, | 13 Roberts Road
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