From b246510ccc8db96bf7a536a305cccf65aab21ce8 Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Mon, 12 Mar 2001 23:02:00 +0000
Subject: [PATCH] Avoid O(N^2) behavior in deferredTriggerAddEvent() for large
numbers of 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.
---
src/backend/commands/trigger.c | 31 +++++++++++++++++++++++--------
1 file changed, 23 insertions(+), 8 deletions(-)
diff --git a/src/backend/commands/trigger.c b/src/backend/commands/trigger.c
index d01ba4ec919..7a013c076bd 100644
--- a/src/backend/commands/trigger.c
+++ b/src/backend/commands/trigger.c
@@ -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;
}
--
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