Mark index entries "killed" when they are no longer visible to any

transaction, so as to avoid returning them out of the index AM.  Saves
repeated heap_fetch operations on frequently-updated rows.  Also detect
queries on unique keys (equality to all columns of a unique index), and
don't bother continuing scan once we have found first match.

Killing is implemented in the btree and hash AMs, but not yet in rtree
or gist, because there isn't an equally convenient place to do it in
those AMs (the outer amgetnext routine can't do it without re-pinning
the index page).

Did some small cleanup on APIs of HeapTupleSatisfies, heap_fetch, and
index_insert to make this a little easier.

src/backend/executor/execUtils.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/executor/execUtils.c,v 1.81 2002/05/12 20:10:02 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/executor/execUtils.c,v 1.82 2002/05/24 18:57:56 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -599,7 +599,7 @@ void
 ExecInsertIndexTuples(TupleTableSlot *slot,
 					  ItemPointer tupleid,
 					  EState *estate,
-					  bool is_update)
+					  bool is_vacuum)
 {
 	HeapTuple	heapTuple;
 	ResultRelInfo *resultRelInfo;
@@ -667,11 +667,17 @@ ExecInsertIndexTuples(TupleTableSlot *slot,
 					   datum,
 					   nullv);
 
+		/*
+		 * The index AM does the rest.  Note we suppress unique-index
+		 * checks if we are being called from VACUUM, since VACUUM may
+		 * need to move dead tuples that have the same keys as live ones.
+		 */
 		result = index_insert(relationDescs[i], /* index relation */
 							  datum,	/* array of heaptuple Datums */
 							  nullv,	/* info on nulls */
 							  &(heapTuple->t_self),		/* tid of heap tuple */
-							  heapRelation);
+							  heapRelation,
+							  relationDescs[i]->rd_uniqueindex && !is_vacuum);
 
 		/*
 		 * keep track of index inserts for debugging