Create new routines systable_beginscan_ordered, systable_getnext_ordered,

systable_endscan_ordered that have API similar to systable_beginscan etc
(in particular, the passed-in scankeys have heap not index attnums),
but guarantee ordered output, unlike the existing functions.  For the moment
these are just very thin wrappers around index_beginscan/index_getnext/etc.
Someday they might need to get smarter; but for now this is just a code
refactoring exercise to reduce the number of direct callers of index_getnext,
in preparation for changing that function's API.

In passing, remove index_getnext_indexitem, which has been dead code for
quite some time, and will have even less use than that in the presence
of run-time-lossy indexes.

1 files changed, 26 insertions, 25 deletions

diff --git a/src/backend/storage/large_object/inv_api.c b/src/backend/storage/large_object/inv_api.c
index 16ad2b03495..00fbfd89ed6 100644
--- a/src/backend/storage/large_object/inv_api.c
+++ b/src/backend/storage/large_object/inv_api.c
@@ -24,7 +24,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/storage/large_object/inv_api.c,v 1.131 2008/03/26 21:10:38 alvherre Exp $
+ *	  $PostgreSQL: pgsql/src/backend/storage/large_object/inv_api.c,v 1.132 2008/04/12 23:14:21 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -201,7 +201,8 @@ inv_create(Oid lobjId)
 	{
 		open_lo_relation();
 
-		lobjId = GetNewOidWithIndex(lo_heap_r, lo_index_r);
+		lobjId = GetNewOidWithIndex(lo_heap_r, LargeObjectLOidPNIndexId,
+									Anum_pg_largeobject_loid);
 	}
 
 	/*
@@ -311,7 +312,7 @@ inv_getsize(LargeObjectDesc *obj_desc)
 	bool		found = false;
 	uint32		lastbyte = 0;
 	ScanKeyData skey[1];
-	IndexScanDesc sd;
+	SysScanDesc sd;
 	HeapTuple	tuple;
 
 	Assert(PointerIsValid(obj_desc));
@@ -323,8 +324,8 @@ inv_getsize(LargeObjectDesc *obj_desc)
 				BTEqualStrategyNumber, F_OIDEQ,
 				ObjectIdGetDatum(obj_desc->id));
 
-	sd = index_beginscan(lo_heap_r, lo_index_r,
-						 obj_desc->snapshot, 1, skey);
+	sd = systable_beginscan_ordered(lo_heap_r, lo_index_r,
+									obj_desc->snapshot, 1, skey);
 
 	/*
 	 * Because the pg_largeobject index is on both loid and pageno, but we
@@ -332,7 +333,7 @@ inv_getsize(LargeObjectDesc *obj_desc)
 	 * large object in reverse pageno order.  So, it's sufficient to examine
 	 * the first valid tuple (== last valid page).
 	 */
-	while ((tuple = index_getnext(sd, BackwardScanDirection)) != NULL)
+	while ((tuple = systable_getnext_ordered(sd, BackwardScanDirection)) != NULL)
 	{
 		Form_pg_largeobject data;
 		bytea	   *datafield;
@@ -356,7 +357,7 @@ inv_getsize(LargeObjectDesc *obj_desc)
 		break;
 	}
 
-	index_endscan(sd);
+	systable_endscan_ordered(sd);
 
 	if (!found)
 		ereport(ERROR,
@@ -415,7 +416,7 @@ inv_read(LargeObjectDesc *obj_desc, char *buf, int nbytes)
 	int32		pageno = (int32) (obj_desc->offset / LOBLKSIZE);
 	uint32		pageoff;
 	ScanKeyData skey[2];
-	IndexScanDesc sd;
+	SysScanDesc sd;
 	HeapTuple	tuple;
 
 	Assert(PointerIsValid(obj_desc));
@@ -436,10 +437,10 @@ inv_read(LargeObjectDesc *obj_desc, char *buf, int nbytes)
 				BTGreaterEqualStrategyNumber, F_INT4GE,
 				Int32GetDatum(pageno));
 
-	sd = index_beginscan(lo_heap_r, lo_index_r,
-						 obj_desc->snapshot, 2, skey);
+	sd = systable_beginscan_ordered(lo_heap_r, lo_index_r,
+									obj_desc->snapshot, 2, skey);
 
-	while ((tuple = index_getnext(sd, ForwardScanDirection)) != NULL)
+	while ((tuple = systable_getnext_ordered(sd, ForwardScanDirection)) != NULL)
 	{
 		Form_pg_largeobject data;
 		bytea	   *datafield;
@@ -450,7 +451,7 @@ inv_read(LargeObjectDesc *obj_desc, char *buf, int nbytes)
 		data = (Form_pg_largeobject) GETSTRUCT(tuple);
 
 		/*
-		 * We assume the indexscan will deliver pages in order.  However,
+		 * We expect the indexscan will deliver pages in order.  However,
 		 * there may be missing pages if the LO contains unwritten "holes". We
 		 * want missing sections to read out as zeroes.
 		 */
@@ -495,7 +496,7 @@ inv_read(LargeObjectDesc *obj_desc, char *buf, int nbytes)
 			break;
 	}
 
-	index_endscan(sd);
+	systable_endscan_ordered(sd);
 
 	return nread;
 }
@@ -509,7 +510,7 @@ inv_write(LargeObjectDesc *obj_desc, const char *buf, int nbytes)
 	int			len;
 	int32		pageno = (int32) (obj_desc->offset / LOBLKSIZE);
 	ScanKeyData skey[2];
-	IndexScanDesc sd;
+	SysScanDesc sd;
 	HeapTuple	oldtuple;
 	Form_pg_largeobject olddata;
 	bool		neednextpage;
@@ -555,8 +556,8 @@ inv_write(LargeObjectDesc *obj_desc, const char *buf, int nbytes)
 				BTGreaterEqualStrategyNumber, F_INT4GE,
 				Int32GetDatum(pageno));
 
-	sd = index_beginscan(lo_heap_r, lo_index_r,
-						 obj_desc->snapshot, 2, skey);
+	sd = systable_beginscan_ordered(lo_heap_r, lo_index_r,
+									obj_desc->snapshot, 2, skey);
 
 	oldtuple = NULL;
 	olddata = NULL;
@@ -565,12 +566,12 @@ inv_write(LargeObjectDesc *obj_desc, const char *buf, int nbytes)
 	while (nwritten < nbytes)
 	{
 		/*
-		 * If possible, get next pre-existing page of the LO.  We assume the
+		 * If possible, get next pre-existing page of the LO.  We expect the
 		 * indexscan will deliver these in order --- but there may be holes.
 		 */
 		if (neednextpage)
 		{
-			if ((oldtuple = index_getnext(sd, ForwardScanDirection)) != NULL)
+			if ((oldtuple = systable_getnext_ordered(sd, ForwardScanDirection)) != NULL)
 			{
 				if (HeapTupleHasNulls(oldtuple))		/* paranoia */
 					elog(ERROR, "null field found in pg_largeobject");
@@ -685,7 +686,7 @@ inv_write(LargeObjectDesc *obj_desc, const char *buf, int nbytes)
 		pageno++;
 	}
 
-	index_endscan(sd);
+	systable_endscan_ordered(sd);
 
 	CatalogCloseIndexes(indstate);
 
@@ -704,7 +705,7 @@ inv_truncate(LargeObjectDesc *obj_desc, int len)
 	int32		pageno = (int32) (len / LOBLKSIZE);
 	int			off;
 	ScanKeyData skey[2];
-	IndexScanDesc sd;
+	SysScanDesc sd;
 	HeapTuple	oldtuple;
 	Form_pg_largeobject olddata;
 	struct
@@ -743,15 +744,15 @@ inv_truncate(LargeObjectDesc *obj_desc, int len)
 				BTGreaterEqualStrategyNumber, F_INT4GE,
 				Int32GetDatum(pageno));
 
-	sd = index_beginscan(lo_heap_r, lo_index_r,
-						 obj_desc->snapshot, 2, skey);
+	sd = systable_beginscan_ordered(lo_heap_r, lo_index_r,
+									obj_desc->snapshot, 2, skey);
 
 	/*
 	 * If possible, get the page the truncation point is in. The truncation
 	 * point may be beyond the end of the LO or in a hole.
 	 */
 	olddata = NULL;
-	if ((oldtuple = index_getnext(sd, ForwardScanDirection)) != NULL)
+	if ((oldtuple = systable_getnext_ordered(sd, ForwardScanDirection)) != NULL)
 	{
 		if (HeapTupleHasNulls(oldtuple))		/* paranoia */
 			elog(ERROR, "null field found in pg_largeobject");
@@ -846,12 +847,12 @@ inv_truncate(LargeObjectDesc *obj_desc, int len)
 	/*
 	 * Delete any pages after the truncation point
 	 */
-	while ((oldtuple = index_getnext(sd, ForwardScanDirection)) != NULL)
+	while ((oldtuple = systable_getnext_ordered(sd, ForwardScanDirection)) != NULL)
 	{
 		simple_heap_delete(lo_heap_r, &oldtuple->t_self);
 	}
 
-	index_endscan(sd);
+	systable_endscan_ordered(sd);
 
 	CatalogCloseIndexes(indstate);