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Avoid O(N^2) behavior with lots of deferred triggers by making
deferredTriggerInvokeEvents only scan events added since it last ran. Stephan Szabo, some corrections by Tom Lane.
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@ -7,7 +7,7 @@
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* IDENTIFICATION
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* $Header: /cvsroot/pgsql/src/backend/commands/trigger.c,v 1.147 2003/03/31 20:47:51 momjian Exp $
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* $Header: /cvsroot/pgsql/src/backend/commands/trigger.c,v 1.148 2003/04/20 17:03:25 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -1626,12 +1626,18 @@ static List *deftrig_trigstates;
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* Because this can grow pretty large, we don't use separate List nodes,
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* but instead thread the list through the dte_next fields of the member
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* nodes. Saves just a few bytes per entry, but that adds up.
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*
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* deftrig_events_imm holds the tail pointer as of the last
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* deferredTriggerInvokeEvents call; we can use this to avoid rescanning
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* entries unnecessarily. It is NULL if deferredTriggerInvokeEvents
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* hasn't run since the last state change.
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*
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* XXX Need to be able to shove this data out to a file if it grows too
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* large...
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* ----------
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*/
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static DeferredTriggerEvent deftrig_events;
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static DeferredTriggerEvent deftrig_events_imm;
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static DeferredTriggerEvent deftrig_event_tail;
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@ -1845,7 +1851,7 @@ static void
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deferredTriggerInvokeEvents(bool immediate_only)
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{
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DeferredTriggerEvent event,
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prev_event = NULL;
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prev_event;
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MemoryContext per_tuple_context;
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Relation rel = NULL;
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TriggerDesc *trigdesc = NULL;
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@ -1857,13 +1863,12 @@ deferredTriggerInvokeEvents(bool immediate_only)
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* are going to discard the whole event queue on return anyway, so no
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* need to bother with "retail" pfree's.
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*
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* In a scenario with many commands in a transaction and many
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* deferred-to-end-of-transaction triggers, it could get annoying to
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* rescan all the deferred triggers at each command end. To speed this
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* up, we could remember the actual end of the queue at EndQuery and
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* examine only events that are newer. On state changes we simply
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* reset the saved position to the beginning of the queue and process
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* all events once with the new states.
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* If immediate_only is true, we need only scan from where the end of
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* the queue was at the previous deferredTriggerInvokeEvents call;
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* any non-deferred events before that point are already fired.
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* (But if the deferral state changes, we must reset the saved position
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* to the beginning of the queue, so as to process all events once with
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* the new states. See DeferredTriggerSetState.)
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*/
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/* Make a per-tuple memory context for trigger function calls */
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@ -1874,7 +1879,22 @@ deferredTriggerInvokeEvents(bool immediate_only)
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ALLOCSET_DEFAULT_INITSIZE,
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ALLOCSET_DEFAULT_MAXSIZE);
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event = deftrig_events;
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/*
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* If immediate_only is true, then the only events that could need firing
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* are those since deftrig_events_imm. (But if deftrig_events_imm is
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* NULL, we must scan the entire list.)
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*/
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if (immediate_only && deftrig_events_imm != NULL)
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{
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prev_event = deftrig_events_imm;
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event = prev_event->dte_next;
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}
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else
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{
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prev_event = NULL;
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event = deftrig_events;
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}
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while (event != NULL)
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{
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bool still_deferred_ones = false;
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@ -1993,6 +2013,9 @@ deferredTriggerInvokeEvents(bool immediate_only)
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/* Update list tail pointer in case we just deleted tail event */
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deftrig_event_tail = prev_event;
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/* Set the immediate event pointer for next time */
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deftrig_events_imm = prev_event;
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/* Release working resources */
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if (rel)
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heap_close(rel, NoLock);
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@ -2051,6 +2074,7 @@ DeferredTriggerBeginXact(void)
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deftrig_trigstates = NIL;
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deftrig_events = NULL;
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deftrig_events_imm = NULL;
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deftrig_event_tail = NULL;
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}
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@ -2280,8 +2304,11 @@ DeferredTriggerSetState(ConstraintsSetStmt *stmt)
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* CONSTRAINTS command applies retroactively. This happens "for free"
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* since we have already made the necessary modifications to the
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* constraints, and deferredTriggerEndQuery() is called by
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* finish_xact_command().
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* finish_xact_command(). But we must reset deferredTriggerInvokeEvents'
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* tail pointer to make it rescan the entire list, in case some deferred
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* events are now immediately invokable.
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*/
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deftrig_events_imm = NULL;
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}
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