A bunch of changes aimed at reducing backend startup time...

Improve 'pg_internal.init' relcache entry preload mechanism so that it is
safe to use for all system catalogs, and arrange to preload a realistic
set of system-catalog entries instead of only the three nailed-in-cache
indexes that were formerly loaded this way.  Fix mechanism for deleting
out-of-date pg_internal.init files: this must be synchronized with transaction
commit, not just done at random times within transactions.  Drive it off
relcache invalidation mechanism so that no special-case tests are needed.

Cache additional information in relcache entries for indexes (their pg_index
tuples and index-operator OIDs) to eliminate repeated lookups.  Also cache
index opclass info at the per-opclass level to avoid repeated lookups during
relcache load.

Generalize 'systable scan' utilities originally developed by Hiroshi,
move them into genam.c, use in a number of places where there was formerly
ugly code for choosing either heap or index scan.  In particular this allows
simplification of the logic that prevents infinite recursion between syscache
and relcache during startup: we can easily switch to heapscans in relcache.c
when and where needed to avoid recursion, so IndexScanOK becomes simpler and
does not need any expensive initialization.

Eliminate useless opening of a heapscan data structure while doing an indexscan
(this saves an mdnblocks call and thus at least one kernel call).

1 files changed, 11 insertions, 88 deletions

diff --git a/src/backend/commands/command.c b/src/backend/commands/command.c
index 9b1a33673c7..f01cf4498fd 100644
--- a/src/backend/commands/command.c
+++ b/src/backend/commands/command.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/commands/Attic/command.c,v 1.153 2002/02/14 15:24:06 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/commands/Attic/command.c,v 1.154 2002/02/19 20:11:12 tgl Exp $
  *
  * NOTES
  *	  The PerformAddAttribute() code, like most of the relation
@@ -29,6 +29,7 @@
 #include "catalog/pg_attrdef.h"
 #include "catalog/pg_index.h"
 #include "catalog/pg_opclass.h"
+#include "catalog/pg_relcheck.h"
 #include "catalog/pg_type.h"
 #include "commands/command.h"
 #include "commands/trigger.h"
@@ -820,93 +821,9 @@ AlterTableAlterColumnStatistics(const char *relationName,
 #ifdef	_DROP_COLUMN_HACK__
 /*
  *	ALTER TABLE DROP COLUMN trial implementation
- *
  */
 
 /*
- *	system table scan(index scan/sequential scan)
- */
-typedef struct SysScanDescData
-{
-	Relation	heap_rel;
-	Relation	irel;
-	HeapScanDesc scan;
-	IndexScanDesc iscan;
-	HeapTupleData tuple;
-	Buffer		buffer;
-}	SysScanDescData, *SysScanDesc;
-
-static void *
-systable_beginscan(Relation rel, const char *indexRelname, int nkeys, ScanKey entry)
-{
-	bool		hasindex = (rel->rd_rel->relhasindex && !IsIgnoringSystemIndexes());
-	SysScanDesc sysscan;
-
-	sysscan = (SysScanDesc) palloc(sizeof(SysScanDescData));
-	sysscan->heap_rel = rel;
-	sysscan->irel = (Relation) NULL;
-	sysscan->tuple.t_datamcxt = NULL;
-	sysscan->tuple.t_data = NULL;
-	sysscan->buffer = InvalidBuffer;
-	if (hasindex)
-	{
-		sysscan->irel = index_openr((char *) indexRelname);
-		sysscan->iscan = index_beginscan(sysscan->irel, false, nkeys, entry);
-	}
-	else
-		sysscan->scan = heap_beginscan(rel, false, SnapshotNow, nkeys, entry);
-	return (void *) sysscan;
-}
-
-static void
-systable_endscan(void *scan)
-{
-	SysScanDesc sysscan = (SysScanDesc) scan;
-
-	if (sysscan->irel)
-	{
-		if (BufferIsValid(sysscan->buffer))
-			ReleaseBuffer(sysscan->buffer);
-		index_endscan(sysscan->iscan);
-		index_close(sysscan->irel);
-	}
-	else
-		heap_endscan(sysscan->scan);
-	pfree(scan);
-}
-
-static HeapTuple
-systable_getnext(void *scan)
-{
-	SysScanDesc sysscan = (SysScanDesc) scan;
-	HeapTuple	htup = (HeapTuple) NULL;
-	RetrieveIndexResult indexRes;
-
-	if (sysscan->irel)
-	{
-		if (BufferIsValid(sysscan->buffer))
-		{
-			ReleaseBuffer(sysscan->buffer);
-			sysscan->buffer = InvalidBuffer;
-		}
-		while (indexRes = index_getnext(sysscan->iscan, ForwardScanDirection), indexRes != NULL)
-		{
-			sysscan->tuple.t_self = indexRes->heap_iptr;
-			heap_fetch(sysscan->heap_rel, SnapshotNow, &sysscan->tuple, &(sysscan->buffer));
-			pfree(indexRes);
-			if (sysscan->tuple.t_data != NULL)
-			{
-				htup = &sysscan->tuple;
-				break;
-			}
-		}
-	}
-	else
-		htup = heap_getnext(sysscan->scan, 0);
-	return htup;
-}
-
-/*
  *	find a specified attribute in a node entry
  */
 static bool
@@ -957,10 +874,15 @@ RemoveColumnReferences(Oid reloid, int attnum, bool checkonly, HeapTuple reltup)
 	/*
 	 * Remove/check constraints here
 	 */
-	ScanKeyEntryInitialize(&entry, (bits16) 0x0, Anum_pg_relcheck_rcrelid,
-					   (RegProcedure) F_OIDEQ, ObjectIdGetDatum(reloid));
+	ScanKeyEntryInitialize(&entry, (bits16) 0x0,
+						   Anum_pg_relcheck_rcrelid,
+						   (RegProcedure) F_OIDEQ,
+						   ObjectIdGetDatum(reloid));
+
 	rcrel = heap_openr(RelCheckRelationName, RowExclusiveLock);
-	sysscan = systable_beginscan(rcrel, RelCheckIndex, 1, &entry);
+	sysscan = systable_beginscan(rcrel, RelCheckIndex, true,
+								 SnapshotNow,
+								 1, &entry);
 
 	while (HeapTupleIsValid(htup = systable_getnext(sysscan)))
 	{
@@ -987,6 +909,7 @@ RemoveColumnReferences(Oid reloid, int attnum, bool checkonly, HeapTuple reltup)
 			}
 		}
 	}
+
 	systable_endscan(sysscan);
 	heap_close(rcrel, NoLock);