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Improve comments about AfterTriggerBeginQuery() query level usage.

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This commit is contained in:
Noah Misch 2014-03-23 02:15:52 -04:00
parent c31305de5f
commit 6115480c54
1 changed files with 11 additions and 5 deletions
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16
src/backend/commands/trigger.c
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@ -3805,10 +3805,14 @@ AfterTriggerEndQuery(EState *estate)
* IMMEDIATE: all events we have decided to defer will be available for it
* to fire.
*
* We loop in case a trigger queues more events at the same query level
* (is that even possible?). Be careful here: firing a trigger could
* result in query_stack being repalloc'd, so we can't save its address
* across afterTriggerInvokeEvents calls.
* We loop in case a trigger queues more events at the same query level.
* Ordinary trigger functions, including all PL/pgSQL trigger functions,
* will instead fire any triggers in a dedicated query level. Foreign key
* enforcement triggers do add to the current query level, thanks to their
* passing fire_triggers = false to SPI_execute_snapshot(). Other
* C-language triggers might do likewise. Be careful here: firing a
* trigger could result in query_stack being repalloc'd, so we can't save
* its address across afterTriggerInvokeEvents calls.
*
* If we find no firable events, we don't have to increment
* firing_counter.
@ -4046,7 +4050,9 @@ AfterTriggerEndSubXact(bool isCommit)
/*
* Release any event lists from queries being aborted, and restore
* query_depth to its pre-subxact value.
* query_depth to its pre-subxact value. This assumes that a
* subtransaction will not add events to query levels started in a
* earlier transaction state.
*/
while (afterTriggers->query_depth > afterTriggers->depth_stack[my_level])
{