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Avoid O(N^2) behavior in deferredTriggerAddEvent() for large numbers of

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tuples inserted/deleted/updated in a single transaction.  On my machine,
this reduced the time to delete 80000 tuples in a foreign-key-referencing
table from ~15min to ~8sec.
This commit is contained in:
Tom Lane 2001-03-12 23:02:00 +00:00
parent 74c732cb87
commit b246510ccc
1 changed files with 23 additions and 8 deletions
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31
src/backend/commands/trigger.c
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@ -7,7 +7,7 @@
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/commands/trigger.c,v 1.86 2001/01/27 05:16:58 tgl Exp $
* $Header: /cvsroot/pgsql/src/backend/commands/trigger.c,v 1.87 2001/03/12 23:02:00 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -1152,14 +1152,16 @@ static bool deftrig_all_isdeferred;
static List *deftrig_trigstates;
/* ----------
* The list of events during the entire transaction.
* The list of events during the entire transaction. deftrig_events
* is the head, deftrig_event_tail is the last entry.
*
* XXX This must finally be held in a file because of the huge
* number of events that could occur in the real world.
* XXX Need to be able to shove this data out to a file if it grows too
* large...
* ----------
*/
static int deftrig_n_events;
static List *deftrig_events;
static List *deftrig_event_tail;
/* ----------
@ -1235,7 +1237,22 @@ deferredTriggerCheckState(Oid tgoid, int32 itemstate)
static void
deferredTriggerAddEvent(DeferredTriggerEvent event)
{
deftrig_events = lappend(deftrig_events, event);
/*
* Since the event list could grow quite long, we keep track of the
* list tail and append there, rather than just doing a stupid "lappend".
* This avoids O(N^2) behavior for large numbers of events.
*/
if (deftrig_event_tail == NIL)
{
/* first list entry */
deftrig_events = makeList1(event);
deftrig_event_tail = deftrig_events;
}
else
{
lnext(deftrig_event_tail) = makeList1(event);
deftrig_event_tail = lnext(deftrig_event_tail);
}
deftrig_n_events++;
}
@ -1397,7 +1414,6 @@ deferredTriggerInvokeEvents(bool immediate_only)
List *el;
DeferredTriggerEvent event;
int still_deferred_ones;
int eventno = -1;
int i;
MemoryContext per_tuple_context;
@ -1421,8 +1437,6 @@ deferredTriggerInvokeEvents(bool immediate_only)
foreach(el, deftrig_events)
{
eventno++;
MemoryContextReset(per_tuple_context);
/* ----------
@ -1548,6 +1562,7 @@ DeferredTriggerBeginXact(void)
deftrig_n_events = 0;
deftrig_events = NIL;
deftrig_event_tail = NIL;
}