Tweak default memory context allocation policy so that a context is not

given any malloc block until something is first allocated in it; but
thereafter, MemoryContextReset won't release that first malloc block.
This preserves the quick-reset property of the original policy, without
forcing 8K to be allocated to every context whether any of it is ever
used or not.  Also, remove some more no-longer-needed explicit freeing
during ExecEndPlan.

src/backend/commands/prepare.c

@@ -6,7 +6,7 @@
  * Copyright (c) 2002, PostgreSQL Global Development Group
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/commands/prepare.c,v 1.11 2002/12/15 16:17:42 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/commands/prepare.c,v 1.12 2002/12/15 21:01:34 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -256,9 +256,9 @@ StoreQuery(const char *stmt_name, List *query_list, List *plan_list,
 	/* Make a permanent memory context for the hashtable entry */
 	entrycxt = AllocSetContextCreate(TopMemoryContext,
 									 stmt_name,
-									 1024,
-									 1024,
-									 ALLOCSET_DEFAULT_MAXSIZE);
+									 ALLOCSET_SMALL_MINSIZE,
+									 ALLOCSET_SMALL_INITSIZE,
+									 ALLOCSET_SMALL_MAXSIZE);
 
 	oldcxt = MemoryContextSwitchTo(entrycxt);
 

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 1.141 2002/11/25 03:36:50 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/commands/trigger.c,v 1.142 2002/12/15 21:01:34 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -2008,13 +2008,9 @@ deferredTriggerInvokeEvents(bool immediate_only)
 void
 DeferredTriggerInit(void)
 {
-	/*
-	 * Since this context will never be reset, give it a minsize of 0.
-	 * This avoids using any memory if the session never stores anything.
-	 */
 	deftrig_gcxt = AllocSetContextCreate(TopMemoryContext,
 										 "DeferredTriggerSession",
-										 0,
+										 ALLOCSET_DEFAULT_MINSIZE,
 										 ALLOCSET_DEFAULT_INITSIZE,
 										 ALLOCSET_DEFAULT_MAXSIZE);
 }
@@ -2041,12 +2037,11 @@ DeferredTriggerBeginXact(void)
 
 	/*
 	 * Create the per transaction memory context and copy all states from
-	 * the per session context to here.  Set the minsize to 0 to avoid
-	 * wasting memory if there is no deferred trigger data.
+	 * the per session context to here.
 	 */
 	deftrig_cxt = AllocSetContextCreate(TopTransactionContext,
 										"DeferredTriggerXact",
-										0,
+										ALLOCSET_DEFAULT_MINSIZE,
 										ALLOCSET_DEFAULT_INITSIZE,
 										ALLOCSET_DEFAULT_MAXSIZE);
 	oldcxt = MemoryContextSwitchTo(deftrig_cxt);

src/backend/executor/execJunk.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/executor/execJunk.c,v 1.33 2002/12/12 15:49:28 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/executor/execJunk.c,v 1.34 2002/12/15 21:01:34 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -63,8 +63,6 @@ JunkFilter *
 ExecInitJunkFilter(List *targetList, TupleDesc tupType,
 				   TupleTableSlot *slot)
 {
-	MemoryContext oldContext;
-	MemoryContext junkContext;
 	JunkFilter *junkfilter;
 	List	   *cleanTargetList;
 	int			len,
@@ -79,19 +77,6 @@ ExecInitJunkFilter(List *targetList, TupleDesc tupType,
 	AttrNumber *cleanMap;
 	Expr	   *expr;
 
-	/*
-	 * Make a memory context that will hold the JunkFilter as well as all
-	 * the subsidiary structures we are about to create.  We use smaller-
-	 * than-default sizing parameters since we don't expect a very large
-	 * volume of stuff here.
-	 */
-	junkContext = AllocSetContextCreate(CurrentMemoryContext,
-										"JunkFilterContext",
-										1024,
-										1024,
-										ALLOCSET_DEFAULT_MAXSIZE);
-	oldContext = MemoryContextSwitchTo(junkContext);
-
 	/*
 	 * First find the "clean" target list, i.e. all the entries in the
 	 * original target list which have a false 'resjunk' NOTE: make copy
@@ -174,33 +159,14 @@ ExecInitJunkFilter(List *targetList, TupleDesc tupType,
 	junkfilter->jf_cleanLength = cleanLength;
 	junkfilter->jf_cleanTupType = cleanTupType;
 	junkfilter->jf_cleanMap = cleanMap;
-	junkfilter->jf_junkContext = junkContext;
 	junkfilter->jf_resultSlot = slot;
 
 	if (slot)
 		ExecSetSlotDescriptor(slot, cleanTupType, false);
 
-	MemoryContextSwitchTo(oldContext);
-
 	return junkfilter;
 }
 
-/*-------------------------------------------------------------------------
- * ExecFreeJunkFilter
- *
- * Release the data structures created by ExecInitJunkFilter.
- *-------------------------------------------------------------------------
- */
-void
-ExecFreeJunkFilter(JunkFilter *junkfilter)
-{
-	/*
-	 * Since the junkfilter is inside its own context, we just have to
-	 * delete the context and we're set.
-	 */
-	MemoryContextDelete(junkfilter->jf_junkContext);
-}
-
 /*-------------------------------------------------------------------------
  * ExecGetJunkAttribute
  *

src/backend/executor/execMain.c

@@ -26,7 +26,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/executor/execMain.c,v 1.193 2002/12/15 16:17:45 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/executor/execMain.c,v 1.194 2002/12/15 21:01:34 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -775,6 +775,12 @@ initResultRelInfo(ResultRelInfo *resultRelInfo,
  *		ExecEndPlan
  *
  *		Cleans up the query plan -- closes files and frees up storage
+ *
+ * NOTE: we are no longer very worried about freeing storage per se
+ * in this code; FreeExecutorState should be guaranteed to release all
+ * memory that needs to be released.  What we are worried about doing
+ * is closing relations and dropping buffer pins.  Thus, for example,
+ * tuple tables must be cleared or dropped to ensure pins are released.
  * ----------------------------------------------------------------
  */
 void
@@ -803,7 +809,7 @@ ExecEndPlan(PlanState *planstate, EState *estate)
 
 	/*
 	 * close the result relation(s) if any, but hold locks until xact
-	 * commit.	Also clean up junkfilters if present.
+	 * commit.
 	 */
 	resultRelInfo = estate->es_result_relations;
 	for (i = estate->es_num_result_relations; i > 0; i--)
@@ -811,9 +817,6 @@ ExecEndPlan(PlanState *planstate, EState *estate)
 		/* Close indices and then the relation itself */
 		ExecCloseIndices(resultRelInfo);
 		heap_close(resultRelInfo->ri_RelationDesc, NoLock);
-		/* Delete the junkfilter if any */
-		if (resultRelInfo->ri_junkFilter != NULL)
-			ExecFreeJunkFilter(resultRelInfo->ri_junkFilter);
 		resultRelInfo++;
 	}
 
@@ -823,16 +826,6 @@ ExecEndPlan(PlanState *planstate, EState *estate)
 	if (estate->es_into_relation_descriptor != NULL)
 		heap_close(estate->es_into_relation_descriptor, NoLock);
 
-	/*
-	 * There might be a junkfilter without a result relation.
-	 */
-	if (estate->es_num_result_relations == 0 &&
-		estate->es_junkFilter != NULL)
-	{
-		ExecFreeJunkFilter(estate->es_junkFilter);
-		estate->es_junkFilter = NULL;
-	}
-
 	/*
 	 * close any relations selected FOR UPDATE, again keeping locks
 	 */

src/backend/executor/spi.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/executor/spi.c,v 1.80 2002/12/15 16:17:46 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/executor/spi.c,v 1.81 2002/12/15 21:01:34 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1489,9 +1489,9 @@ _SPI_copy_plan(_SPI_plan *plan, int location)
 	 */
 	plancxt = AllocSetContextCreate(parentcxt,
 									"SPI Plan",
-									1024,
-									1024,
-									ALLOCSET_DEFAULT_MAXSIZE);
+									ALLOCSET_SMALL_MINSIZE,
+									ALLOCSET_SMALL_INITSIZE,
+									ALLOCSET_SMALL_MAXSIZE);
 	oldcxt = MemoryContextSwitchTo(plancxt);
 
 	/* Copy the SPI plan into its own context */

src/backend/utils/cache/relcache.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/utils/cache/relcache.c,v 1.181 2002/11/15 17:18:49 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/utils/cache/relcache.c,v 1.182 2002/12/15 21:01:34 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -647,9 +647,9 @@ RelationBuildRuleLock(Relation relation)
 	 */
 	rulescxt = AllocSetContextCreate(CacheMemoryContext,
 									 RelationGetRelationName(relation),
-									 0, /* minsize */
-									 1024,		/* initsize */
-									 1024);		/* maxsize */
+									 ALLOCSET_SMALL_MINSIZE,
+									 ALLOCSET_SMALL_INITSIZE,
+									 ALLOCSET_SMALL_MAXSIZE);
 	relation->rd_rulescxt = rulescxt;
 
 	/*
@@ -994,9 +994,9 @@ RelationInitIndexAccessInfo(Relation relation)
 	 */
 	indexcxt = AllocSetContextCreate(CacheMemoryContext,
 									 RelationGetRelationName(relation),
-									 0, /* minsize */
-									 512,		/* initsize */
-									 1024);		/* maxsize */
+									 ALLOCSET_SMALL_MINSIZE,
+									 ALLOCSET_SMALL_INITSIZE,
+									 ALLOCSET_SMALL_MAXSIZE);
 	relation->rd_indexcxt = indexcxt;
 
 	/*
@@ -2851,9 +2851,9 @@ load_relcache_init_file(void)
 			 */
 			indexcxt = AllocSetContextCreate(CacheMemoryContext,
 											 RelationGetRelationName(rel),
-											 0, /* minsize */
-											 512,		/* initsize */
-											 1024);		/* maxsize */
+											 ALLOCSET_SMALL_MINSIZE,
+											 ALLOCSET_SMALL_INITSIZE,
+											 ALLOCSET_SMALL_MAXSIZE);
 			rel->rd_indexcxt = indexcxt;
 
 			/* next, read the index strategy map */

src/backend/utils/mmgr/aset.c

@@ -11,7 +11,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/utils/mmgr/aset.c,v 1.48 2002/09/04 20:31:33 momjian Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/utils/mmgr/aset.c,v 1.49 2002/12/15 21:01:34 tgl Exp $
  *
  * NOTE:
  *	This is a new (Feb. 05, 1999) implementation of the allocation set
@@ -371,10 +371,11 @@ AllocSetInit(MemoryContext context)
  *		Frees all memory which is allocated in the given set.
  *
  * Actually, this routine has some discretion about what to do.
- * It should mark all allocated chunks freed, but it need not
- * necessarily give back all the resources the set owns.  Our
- * actual implementation is that we hang on to any "keeper"
- * block specified for the set.
+ * It should mark all allocated chunks freed, but it need not necessarily
+ * give back all the resources the set owns.  Our actual implementation is
+ * that we hang onto any "keeper" block specified for the set.  In this way,
+ * we don't thrash malloc() when a context is repeatedly reset after small
+ * allocations, which is typical behavior for per-tuple contexts.
  */
 static void
 AllocSetReset(MemoryContext context)
@@ -697,6 +698,21 @@ AllocSetAlloc(MemoryContext context, Size size)
 		block->freeptr = ((char *) block) + ALLOC_BLOCKHDRSZ;
 		block->endptr = ((char *) block) + blksize;
 
+		/*
+		 * If this is the first block of the set, make it the "keeper" block.
+		 * Formerly, a keeper block could only be created during context
+		 * creation, but allowing it to happen here lets us have fast reset
+		 * cycling even for contexts created with minContextSize = 0; that
+		 * way we don't have to force space to be allocated in contexts that
+		 * might never need any space.  Don't mark an oversize block as
+		 * a keeper, however.
+		 */
+		if (set->blocks == NULL && blksize == set->initBlockSize)
+		{
+			Assert(set->keeper == NULL);
+			set->keeper = block;
+		}
+
 		block->next = set->blocks;
 		set->blocks = block;
 	}

src/backend/utils/mmgr/mcxt.c

@@ -14,7 +14,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/utils/mmgr/mcxt.c,v 1.36 2002/11/13 00:37:06 momjian Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/utils/mmgr/mcxt.c,v 1.37 2002/12/15 21:01:34 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -80,7 +80,7 @@ MemoryContextInit(void)
 	 */
 	TopMemoryContext = AllocSetContextCreate((MemoryContext) NULL,
 											 "TopMemoryContext",
-											 8 * 1024,
+											 0,
 											 8 * 1024,
 											 8 * 1024);
 

src/include/executor/executor.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $Id: executor.h,v 1.84 2002/12/15 16:17:54 tgl Exp $
+ * $Id: executor.h,v 1.85 2002/12/15 21:01:34 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -41,7 +41,6 @@ extern bool ExecSupportsMarkRestore(NodeTag plantype);
  */
 extern JunkFilter *ExecInitJunkFilter(List *targetList, TupleDesc tupType,
 				   TupleTableSlot *slot);
-extern void ExecFreeJunkFilter(JunkFilter *junkfilter);
 extern bool ExecGetJunkAttribute(JunkFilter *junkfilter, TupleTableSlot *slot,
 					 char *attrName, Datum *value, bool *isNull);
 extern HeapTuple ExecRemoveJunk(JunkFilter *junkfilter, TupleTableSlot *slot);

src/include/nodes/execnodes.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $Id: execnodes.h,v 1.86 2002/12/15 16:17:56 tgl Exp $
+ * $Id: execnodes.h,v 1.87 2002/12/15 21:01:34 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -218,16 +218,7 @@ typedef struct ProjectionInfo
  *	  cleanMap:			A map with the correspondence between the non-junk
  *						attribute numbers of the "original" tuple and the
  *						attribute numbers of the "clean" tuple.
- *	  junkContext:		memory context holding the JunkFilter node and all
- *						its subsidiary data structures.
  *	  resultSlot:		tuple slot that can be used to hold cleaned tuple.
- *
- * NOTE: the original targetList and tupType are passed to ExecInitJunkFilter,
- * as is the resultSlot.  These items do not belong to the JunkFilter.	All
- * the other subsidiary structures are created during ExecInitJunkFilter,
- * and all of them can be freed by deleting the memory context junkContext.
- * This would not be needed if we had a cleaner approach to managing
- * query-lifetime data structures...
  * ----------------
  */
 typedef struct JunkFilter
@@ -240,7 +231,6 @@ typedef struct JunkFilter
 	int			jf_cleanLength;
 	TupleDesc	jf_cleanTupType;
 	AttrNumber *jf_cleanMap;
-	MemoryContext jf_junkContext;
 	TupleTableSlot *jf_resultSlot;
 } JunkFilter;
 

src/include/utils/memutils.h

@@ -10,7 +10,7 @@
  * Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $Id: memutils.h,v 1.48 2002/09/04 20:31:45 momjian Exp $
+ * $Id: memutils.h,v 1.49 2002/12/15 21:01:34 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -116,8 +116,16 @@ extern MemoryContext AllocSetContextCreate(MemoryContext parent,
  * Recommended default alloc parameters, suitable for "ordinary" contexts
  * that might hold quite a lot of data.
  */
-#define ALLOCSET_DEFAULT_MINSIZE   (8 * 1024)
+#define ALLOCSET_DEFAULT_MINSIZE   0
 #define ALLOCSET_DEFAULT_INITSIZE  (8 * 1024)
 #define ALLOCSET_DEFAULT_MAXSIZE   (8 * 1024 * 1024)
 
+/*
+ * Recommended alloc parameters for "small" contexts that are not expected
+ * to contain much data (for example, a context to contain a query plan).
+ */
+#define ALLOCSET_SMALL_MINSIZE   0
+#define ALLOCSET_SMALL_INITSIZE  (1 * 1024)
+#define ALLOCSET_SMALL_MAXSIZE   (8 * 1024)
+
 #endif   /* MEMUTILS_H */