Rearrange the implementation of index-only scans.

This commit changes index-only scans so that data is read directly from the
index tuple without first generating a faux heap tuple.  The only immediate
benefit is that indexes on system columns (such as OID) can be used in
index-only scans, but this is necessary infrastructure if we are ever to
support index-only scans on expression indexes.  The executor is now ready
for that, though the planner still needs substantial work to recognize
the possibility.

To do this, Vars in index-only plan nodes have to refer to index columns
not heap columns.  I introduced a new special varno, INDEX_VAR, to mark
such Vars to avoid confusion.  (In passing, this commit renames the two
existing special varnos to OUTER_VAR and INNER_VAR.)  This allows
ruleutils.c to handle them with logic similar to what we use for subplan
reference Vars.

Since index-only scans are now fundamentally different from regular
indexscans so far as their expression subtrees are concerned, I also chose
to change them to have their own plan node type (and hence, their own
executor source file).

src/backend/commands/explain.c

@@ -79,6 +79,8 @@ static void show_instrumentation_count(const char *qlabel, int which,
 						   PlanState *planstate, ExplainState *es);
 static void show_foreignscan_info(ForeignScanState *fsstate, ExplainState *es);
 static const char *explain_get_index_name(Oid indexId);
+static void ExplainIndexScanDetails(Oid indexid, ScanDirection indexorderdir,
+						ExplainState *es);
 static void ExplainScanTarget(Scan *plan, ExplainState *es);
 static void ExplainModifyTarget(ModifyTable *plan, ExplainState *es);
 static void ExplainTargetRel(Plan *plan, Index rti, ExplainState *es);
@@ -656,10 +658,10 @@ ExplainNode(PlanState *planstate, List *ancestors,
 			pname = sname = "Seq Scan";
 			break;
 		case T_IndexScan:
-			if (((IndexScan *) plan)->indexonly)
+			pname = sname = "Index Scan";
-				pname = sname = "Index Only Scan";
+			break;
-			else
+		case T_IndexOnlyScan:
-				pname = sname = "Index Scan";
+			pname = sname = "Index Only Scan";
 			break;
 		case T_BitmapIndexScan:
 			pname = sname = "Bitmap Index Scan";
@@ -793,42 +795,6 @@ ExplainNode(PlanState *planstate, List *ancestors,
 
 	switch (nodeTag(plan))
 	{
-		case T_IndexScan:
-			{
-				IndexScan  *indexscan = (IndexScan *) plan;
-				const char *indexname =
-				explain_get_index_name(indexscan->indexid);
-
-				if (es->format == EXPLAIN_FORMAT_TEXT)
-				{
-					if (ScanDirectionIsBackward(indexscan->indexorderdir))
-						appendStringInfoString(es->str, " Backward");
-					appendStringInfo(es->str, " using %s", indexname);
-				}
-				else
-				{
-					const char *scandir;
-
-					switch (indexscan->indexorderdir)
-					{
-						case BackwardScanDirection:
-							scandir = "Backward";
-							break;
-						case NoMovementScanDirection:
-							scandir = "NoMovement";
-							break;
-						case ForwardScanDirection:
-							scandir = "Forward";
-							break;
-						default:
-							scandir = "???";
-							break;
-					}
-					ExplainPropertyText("Scan Direction", scandir, es);
-					ExplainPropertyText("Index Name", indexname, es);
-				}
-			}
-			/* FALL THRU */
 		case T_SeqScan:
 		case T_BitmapHeapScan:
 		case T_TidScan:
@@ -840,6 +806,26 @@ ExplainNode(PlanState *planstate, List *ancestors,
 		case T_ForeignScan:
 			ExplainScanTarget((Scan *) plan, es);
 			break;
+		case T_IndexScan:
+			{
+				IndexScan  *indexscan = (IndexScan *) plan;
+
+				ExplainIndexScanDetails(indexscan->indexid,
+										indexscan->indexorderdir,
+										es);
+				ExplainScanTarget((Scan *) indexscan, es);
+			}
+			break;
+		case T_IndexOnlyScan:
+			{
+				IndexOnlyScan *indexonlyscan = (IndexOnlyScan *) plan;
+
+				ExplainIndexScanDetails(indexonlyscan->indexid,
+										indexonlyscan->indexorderdir,
+										es);
+				ExplainScanTarget((Scan *) indexonlyscan, es);
+			}
+			break;
 		case T_BitmapIndexScan:
 			{
 				BitmapIndexScan *bitmapindexscan = (BitmapIndexScan *) plan;
@@ -1014,6 +1000,19 @@ ExplainNode(PlanState *planstate, List *ancestors,
 				show_instrumentation_count("Rows Removed by Filter", 1,
 										   planstate, es);
 			break;
+		case T_IndexOnlyScan:
+			show_scan_qual(((IndexOnlyScan *) plan)->indexqual,
+						   "Index Cond", planstate, ancestors, es);
+			if (((IndexOnlyScan *) plan)->indexqual)
+				show_instrumentation_count("Rows Removed by Index Recheck", 2,
+										   planstate, es);
+			show_scan_qual(((IndexOnlyScan *) plan)->indexorderby,
+						   "Order By", planstate, ancestors, es);
+			show_scan_qual(plan->qual, "Filter", planstate, ancestors, es);
+			if (plan->qual)
+				show_instrumentation_count("Rows Removed by Filter", 1,
+										   planstate, es);
+			break;
 		case T_BitmapIndexScan:
 			show_scan_qual(((BitmapIndexScan *) plan)->indexqualorig,
 						   "Index Cond", planstate, ancestors, es);
@@ -1626,6 +1625,45 @@ explain_get_index_name(Oid indexId)
 	return result;
 }
 
+/*
+ * Add some additional details about an IndexScan or IndexOnlyScan
+ */
+static void
+ExplainIndexScanDetails(Oid indexid, ScanDirection indexorderdir,
+						ExplainState *es)
+{
+	const char *indexname = explain_get_index_name(indexid);
+
+	if (es->format == EXPLAIN_FORMAT_TEXT)
+	{
+		if (ScanDirectionIsBackward(indexorderdir))
+			appendStringInfoString(es->str, " Backward");
+		appendStringInfo(es->str, " using %s", indexname);
+	}
+	else
+	{
+		const char *scandir;
+
+		switch (indexorderdir)
+		{
+			case BackwardScanDirection:
+				scandir = "Backward";
+				break;
+			case NoMovementScanDirection:
+				scandir = "NoMovement";
+				break;
+			case ForwardScanDirection:
+				scandir = "Forward";
+				break;
+			default:
+				scandir = "???";
+				break;
+		}
+		ExplainPropertyText("Scan Direction", scandir, es);
+		ExplainPropertyText("Index Name", indexname, es);
+	}
+}
+
 /*
  * Show the target of a Scan node
  */
@@ -1670,6 +1708,7 @@ ExplainTargetRel(Plan *plan, Index rti, ExplainState *es)
 	{
 		case T_SeqScan:
 		case T_IndexScan:
+		case T_IndexOnlyScan:
 		case T_BitmapHeapScan:
 		case T_TidScan:
 		case T_ForeignScan:

src/backend/commands/trigger.c

@@ -2734,9 +2734,9 @@ TriggerEnabled(EState *estate, ResultRelInfo *relinfo,
 
 			oldContext = MemoryContextSwitchTo(estate->es_query_cxt);
 			tgqual = stringToNode(trigger->tgqual);
-			/* Change references to OLD and NEW to INNER and OUTER */
+			/* Change references to OLD and NEW to INNER_VAR and OUTER_VAR */
-			ChangeVarNodes(tgqual, PRS2_OLD_VARNO, INNER, 0);
+			ChangeVarNodes(tgqual, PRS2_OLD_VARNO, INNER_VAR, 0);
-			ChangeVarNodes(tgqual, PRS2_NEW_VARNO, OUTER, 0);
+			ChangeVarNodes(tgqual, PRS2_NEW_VARNO, OUTER_VAR, 0);
 			/* ExecQual wants implicit-AND form */
 			tgqual = (Node *) make_ands_implicit((Expr *) tgqual);
 			*predicate = (List *) ExecPrepareExpr((Expr *) tgqual, estate);
@@ -2783,7 +2783,7 @@ TriggerEnabled(EState *estate, ResultRelInfo *relinfo,
 
 		/*
 		 * Finally evaluate the expression, making the old and/or new tuples
-		 * available as INNER/OUTER respectively.
+		 * available as INNER_VAR/OUTER_VAR respectively.
 		 */
 		econtext->ecxt_innertuple = oldslot;
 		econtext->ecxt_outertuple = newslot;

src/backend/executor/Makefile

@@ -17,7 +17,8 @@ OBJS = execAmi.o execCurrent.o execGrouping.o execJunk.o execMain.o \
        execUtils.o functions.o instrument.o nodeAppend.o nodeAgg.o \
        nodeBitmapAnd.o nodeBitmapOr.o \
        nodeBitmapHeapscan.o nodeBitmapIndexscan.o nodeHash.o \
-       nodeHashjoin.o nodeIndexscan.o nodeLimit.o nodeLockRows.o \
+       nodeHashjoin.o nodeIndexscan.o nodeIndexonlyscan.o \
+       nodeLimit.o nodeLockRows.o \
        nodeMaterial.o nodeMergeAppend.o nodeMergejoin.o nodeModifyTable.o \
        nodeNestloop.o nodeFunctionscan.o nodeRecursiveunion.o nodeResult.o \
        nodeSeqscan.o nodeSetOp.o nodeSort.o nodeUnique.o \

src/backend/executor/execAmi.c

@@ -26,6 +26,7 @@
 #include "executor/nodeGroup.h"
 #include "executor/nodeHash.h"
 #include "executor/nodeHashjoin.h"
+#include "executor/nodeIndexonlyscan.h"
 #include "executor/nodeIndexscan.h"
 #include "executor/nodeLimit.h"
 #include "executor/nodeLockRows.h"
@@ -155,6 +156,10 @@ ExecReScan(PlanState *node)
 			ExecReScanIndexScan((IndexScanState *) node);
 			break;
 
+		case T_IndexOnlyScanState:
+			ExecReScanIndexOnlyScan((IndexOnlyScanState *) node);
+			break;
+
 		case T_BitmapIndexScanState:
 			ExecReScanBitmapIndexScan((BitmapIndexScanState *) node);
 			break;
@@ -273,6 +278,10 @@ ExecMarkPos(PlanState *node)
 			ExecIndexMarkPos((IndexScanState *) node);
 			break;
 
+		case T_IndexOnlyScanState:
+			ExecIndexOnlyMarkPos((IndexOnlyScanState *) node);
+			break;
+
 		case T_TidScanState:
 			ExecTidMarkPos((TidScanState *) node);
 			break;
@@ -326,6 +335,10 @@ ExecRestrPos(PlanState *node)
 			ExecIndexRestrPos((IndexScanState *) node);
 			break;
 
+		case T_IndexOnlyScanState:
+			ExecIndexOnlyRestrPos((IndexOnlyScanState *) node);
+			break;
+
 		case T_TidScanState:
 			ExecTidRestrPos((TidScanState *) node);
 			break;
@@ -371,6 +384,7 @@ ExecSupportsMarkRestore(NodeTag plantype)
 	{
 		case T_SeqScan:
 		case T_IndexScan:
+		case T_IndexOnlyScan:
 		case T_TidScan:
 		case T_ValuesScan:
 		case T_Material:
@@ -442,6 +456,10 @@ ExecSupportsBackwardScan(Plan *node)
 			return IndexSupportsBackwardScan(((IndexScan *) node)->indexid) &&
 				TargetListSupportsBackwardScan(node->targetlist);
 
+		case T_IndexOnlyScan:
+			return IndexSupportsBackwardScan(((IndexOnlyScan *) node)->indexid) &&
+				TargetListSupportsBackwardScan(node->targetlist);
+
 		case T_SubqueryScan:
 			return ExecSupportsBackwardScan(((SubqueryScan *) node)->subplan) &&
 				TargetListSupportsBackwardScan(node->targetlist);
@@ -474,7 +492,8 @@ TargetListSupportsBackwardScan(List *targetlist)
 }
 
 /*
- * An IndexScan node supports backward scan only if the index's AM does.
+ * An IndexScan or IndexOnlyScan node supports backward scan only if the
+ * index's AM does.
  */
 static bool
 IndexSupportsBackwardScan(Oid indexid)

src/backend/executor/execCurrent.c

@@ -262,6 +262,7 @@ search_plan_tree(PlanState *node, Oid table_oid)
 			 */
 		case T_SeqScanState:
 		case T_IndexScanState:
+		case T_IndexOnlyScanState:
 		case T_BitmapHeapScanState:
 		case T_TidScanState:
 			{

src/backend/executor/execProcnode.c

@@ -89,6 +89,7 @@
 #include "executor/nodeGroup.h"
 #include "executor/nodeHash.h"
 #include "executor/nodeHashjoin.h"
+#include "executor/nodeIndexonlyscan.h"
 #include "executor/nodeIndexscan.h"
 #include "executor/nodeLimit.h"
 #include "executor/nodeLockRows.h"
@@ -192,6 +193,11 @@ ExecInitNode(Plan *node, EState *estate, int eflags)
 													 estate, eflags);
 			break;
 
+		case T_IndexOnlyScan:
+			result = (PlanState *) ExecInitIndexOnlyScan((IndexOnlyScan *) node,
+														 estate, eflags);
+			break;
+
 		case T_BitmapIndexScan:
 			result = (PlanState *) ExecInitBitmapIndexScan((BitmapIndexScan *) node,
 														   estate, eflags);
@@ -397,6 +403,10 @@ ExecProcNode(PlanState *node)
 			result = ExecIndexScan((IndexScanState *) node);
 			break;
 
+		case T_IndexOnlyScanState:
+			result = ExecIndexOnlyScan((IndexOnlyScanState *) node);
+			break;
+
 			/* BitmapIndexScanState does not yield tuples */
 
 		case T_BitmapHeapScanState:
@@ -627,6 +637,10 @@ ExecEndNode(PlanState *node)
 			ExecEndIndexScan((IndexScanState *) node);
 			break;
 
+		case T_IndexOnlyScanState:
+			ExecEndIndexOnlyScan((IndexOnlyScanState *) node);
+			break;
+
 		case T_BitmapIndexScanState:
 			ExecEndBitmapIndexScan((BitmapIndexScanState *) node);
 			break;

src/backend/executor/execQual.c

@@ -578,14 +578,16 @@ ExecEvalVar(ExprState *exprstate, ExprContext *econtext,
 	/* Get the input slot and attribute number we want */
 	switch (variable->varno)
 	{
-		case INNER:				/* get the tuple from the inner node */
+		case INNER_VAR:			/* get the tuple from the inner node */
 			slot = econtext->ecxt_innertuple;
 			break;
 
-		case OUTER:				/* get the tuple from the outer node */
+		case OUTER_VAR:			/* get the tuple from the outer node */
 			slot = econtext->ecxt_outertuple;
 			break;
 
+		/* INDEX_VAR is handled by default case */
+
 		default:				/* get the tuple from the relation being
 								 * scanned */
 			slot = econtext->ecxt_scantuple;
@@ -761,14 +763,16 @@ ExecEvalScalarVar(ExprState *exprstate, ExprContext *econtext,
 	/* Get the input slot and attribute number we want */
 	switch (variable->varno)
 	{
-		case INNER:				/* get the tuple from the inner node */
+		case INNER_VAR:			/* get the tuple from the inner node */
 			slot = econtext->ecxt_innertuple;
 			break;
 
-		case OUTER:				/* get the tuple from the outer node */
+		case OUTER_VAR:			/* get the tuple from the outer node */
 			slot = econtext->ecxt_outertuple;
 			break;
 
+		/* INDEX_VAR is handled by default case */
+
 		default:				/* get the tuple from the relation being
 								 * scanned */
 			slot = econtext->ecxt_scantuple;
@@ -804,14 +808,16 @@ ExecEvalWholeRowVar(ExprState *exprstate, ExprContext *econtext,
 	/* Get the input slot we want */
 	switch (variable->varno)
 	{
-		case INNER:				/* get the tuple from the inner node */
+		case INNER_VAR:			/* get the tuple from the inner node */
 			slot = econtext->ecxt_innertuple;
 			break;
 
-		case OUTER:				/* get the tuple from the outer node */
+		case OUTER_VAR:			/* get the tuple from the outer node */
 			slot = econtext->ecxt_outertuple;
 			break;
 
+		/* INDEX_VAR is handled by default case */
+
 		default:				/* get the tuple from the relation being
 								 * scanned */
 			slot = econtext->ecxt_scantuple;
@@ -873,14 +879,16 @@ ExecEvalWholeRowSlow(ExprState *exprstate, ExprContext *econtext,
 	/* Get the input slot we want */
 	switch (variable->varno)
 	{
-		case INNER:				/* get the tuple from the inner node */
+		case INNER_VAR:			/* get the tuple from the inner node */
 			slot = econtext->ecxt_innertuple;
 			break;
 
-		case OUTER:				/* get the tuple from the outer node */
+		case OUTER_VAR:			/* get the tuple from the outer node */
 			slot = econtext->ecxt_outertuple;
 			break;
 
+		/* INDEX_VAR is handled by default case */
+
 		default:				/* get the tuple from the relation being
 								 * scanned */
 			slot = econtext->ecxt_scantuple;

src/backend/executor/execScan.c

@@ -246,10 +246,17 @@ void
 ExecAssignScanProjectionInfo(ScanState *node)
 {
 	Scan	   *scan = (Scan *) node->ps.plan;
+	Index		varno;
+
+	/* Vars in an index-only scan's tlist should be INDEX_VAR */
+	if (IsA(scan, IndexOnlyScan))
+		varno = INDEX_VAR;
+	else
+		varno = scan->scanrelid;
 
 	if (tlist_matches_tupdesc(&node->ps,
 							  scan->plan.targetlist,
-							  scan->scanrelid,
+							  varno,
 							  node->ss_ScanTupleSlot->tts_tupleDescriptor))
 		node->ps.ps_ProjInfo = NULL;
 	else

src/backend/executor/execUtils.c

@@ -566,20 +566,22 @@ ExecBuildProjectionInfo(List *targetList,
 
 			switch (variable->varno)
 			{
-				case INNER:
+				case INNER_VAR:
 					varSlotOffsets[numSimpleVars] = offsetof(ExprContext,
 															 ecxt_innertuple);
 					if (projInfo->pi_lastInnerVar < attnum)
 						projInfo->pi_lastInnerVar = attnum;
 					break;
 
-				case OUTER:
+				case OUTER_VAR:
 					varSlotOffsets[numSimpleVars] = offsetof(ExprContext,
 															 ecxt_outertuple);
 					if (projInfo->pi_lastOuterVar < attnum)
 						projInfo->pi_lastOuterVar = attnum;
 					break;
 
+				/* INDEX_VAR is handled by default case */
+
 				default:
 					varSlotOffsets[numSimpleVars] = offsetof(ExprContext,
 															 ecxt_scantuple);
@@ -628,16 +630,18 @@ get_last_attnums(Node *node, ProjectionInfo *projInfo)
 
 		switch (variable->varno)
 		{
-			case INNER:
+			case INNER_VAR:
 				if (projInfo->pi_lastInnerVar < attnum)
 					projInfo->pi_lastInnerVar = attnum;
 				break;
 
-			case OUTER:
+			case OUTER_VAR:
 				if (projInfo->pi_lastOuterVar < attnum)
 					projInfo->pi_lastOuterVar = attnum;
 				break;
 
+			/* INDEX_VAR is handled by default case */
+
 			default:
 				if (projInfo->pi_lastScanVar < attnum)
 					projInfo->pi_lastScanVar = attnum;

src/backend/executor/nodeAgg.c

@@ -806,8 +806,8 @@ find_unaggregated_cols_walker(Node *node, Bitmapset **colnos)
 	{
 		Var		   *var = (Var *) node;
 
-		/* setrefs.c should have set the varno to OUTER */
+		/* setrefs.c should have set the varno to OUTER_VAR */
-		Assert(var->varno == OUTER);
+		Assert(var->varno == OUTER_VAR);
 		Assert(var->varlevelsup == 0);
 		*colnos = bms_add_member(*colnos, var->varattno);
 		return false;

src/backend/executor/nodeBitmapIndexscan.c

@@ -266,7 +266,6 @@ ExecInitBitmapIndexScan(BitmapIndexScan *node, EState *estate, int eflags)
 	 */
 	ExecIndexBuildScanKeys((PlanState *) indexstate,
 						   indexstate->biss_RelationDesc,
-						   node->scan.scanrelid,
 						   node->indexqual,
 						   false,
 						   &indexstate->biss_ScanKeys,

src/backend/executor/nodeHash.c

@@ -755,8 +755,8 @@ ExecHashTableInsert(HashJoinTable hashtable,
  *		Compute the hash value for a tuple
  *
  * The tuple to be tested must be in either econtext->ecxt_outertuple or
- * econtext->ecxt_innertuple.  Vars in the hashkeys expressions reference
+ * econtext->ecxt_innertuple.  Vars in the hashkeys expressions should have
- * either OUTER or INNER.
+ * varno either OUTER_VAR or INNER_VAR.
  *
  * A TRUE result means the tuple's hash value has been successfully computed
  * and stored at *hashvalue.  A FALSE result means the tuple cannot match

src/backend/executor/nodeIndexonlyscan.c

@@ -0,0 +1,542 @@
+/*-------------------------------------------------------------------------
+ *
+ * nodeIndexonlyscan.c
+ *	  Routines to support index-only scans
+ *
+ * Portions Copyright (c) 1996-2011, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/executor/nodeIndexonlyscan.c
+ *
+ *-------------------------------------------------------------------------
+ */
+/*
+ * INTERFACE ROUTINES
+ *		ExecIndexOnlyScan			scans an index
+ *		IndexOnlyNext				retrieve next tuple
+ *		ExecInitIndexOnlyScan		creates and initializes state info.
+ *		ExecReScanIndexOnlyScan		rescans the indexed relation.
+ *		ExecEndIndexOnlyScan		releases all storage.
+ *		ExecIndexOnlyMarkPos		marks scan position.
+ *		ExecIndexOnlyRestrPos		restores scan position.
+ */
+#include "postgres.h"
+
+#include "access/relscan.h"
+#include "access/visibilitymap.h"
+#include "catalog/pg_opfamily.h"
+#include "catalog/pg_type.h"
+#include "executor/execdebug.h"
+#include "executor/nodeIndexonlyscan.h"
+#include "executor/nodeIndexscan.h"
+#include "storage/bufmgr.h"
+#include "utils/memutils.h"
+#include "utils/rel.h"
+
+
+static TupleTableSlot *IndexOnlyNext(IndexOnlyScanState *node);
+static void StoreIndexTuple(TupleTableSlot *slot, IndexTuple itup,
+							Relation indexRel);
+
+
+/* ----------------------------------------------------------------
+ *		IndexOnlyNext
+ *
+ *		Retrieve a tuple from the IndexOnlyScan node's index.
+ * ----------------------------------------------------------------
+ */
+static TupleTableSlot *
+IndexOnlyNext(IndexOnlyScanState *node)
+{
+	EState	   *estate;
+	ExprContext *econtext;
+	ScanDirection direction;
+	IndexScanDesc scandesc;
+	HeapTuple	tuple;
+	TupleTableSlot *slot;
+	ItemPointer tid;
+
+	/*
+	 * extract necessary information from index scan node
+	 */
+	estate = node->ss.ps.state;
+	direction = estate->es_direction;
+	/* flip direction if this is an overall backward scan */
+	if (ScanDirectionIsBackward(((IndexOnlyScan *) node->ss.ps.plan)->indexorderdir))
+	{
+		if (ScanDirectionIsForward(direction))
+			direction = BackwardScanDirection;
+		else if (ScanDirectionIsBackward(direction))
+			direction = ForwardScanDirection;
+	}
+	scandesc = node->ioss_ScanDesc;
+	econtext = node->ss.ps.ps_ExprContext;
+	slot = node->ss.ss_ScanTupleSlot;
+
+	/*
+	 * OK, now that we have what we need, fetch the next tuple.
+	 */
+	while ((tid = index_getnext_tid(scandesc, direction)) != NULL)
+	{
+		/*
+		 * We can skip the heap fetch if the TID references a heap page on
+		 * which all tuples are known visible to everybody.  In any case,
+		 * we'll use the index tuple not the heap tuple as the data source.
+		 */
+		if (!visibilitymap_test(scandesc->heapRelation,
+								ItemPointerGetBlockNumber(tid),
+								&node->ioss_VMBuffer))
+		{
+			/*
+			 * Rats, we have to visit the heap to check visibility.
+			 */
+			tuple = index_fetch_heap(scandesc);
+			if (tuple == NULL)
+				continue;	/* no visible tuple, try next index entry */
+
+			/*
+			 * Only MVCC snapshots are supported here, so there should be no
+			 * need to keep following the HOT chain once a visible entry has
+			 * been found.  If we did want to allow that, we'd need to keep
+			 * more state to remember not to call index_getnext_tid next time.
+			 */
+			if (scandesc->xs_continue_hot)
+				elog(ERROR, "non-MVCC snapshots are not supported in index-only scans");
+
+			/*
+			 * Note: at this point we are holding a pin on the heap page, as
+			 * recorded in scandesc->xs_cbuf.  We could release that pin now,
+			 * but it's not clear whether it's a win to do so.  The next index
+			 * entry might require a visit to the same heap page.
+			 */
+		}
+
+		/*
+		 * Fill the scan tuple slot with data from the index.
+		 */
+		StoreIndexTuple(slot, scandesc->xs_itup, scandesc->indexRelation);
+
+		/*
+		 * If the index was lossy, we have to recheck the index quals.
+		 * (Currently, this can never happen, but we should support the case
+		 * for possible future use, eg with GiST indexes.)
+		 */
+		if (scandesc->xs_recheck)
+		{
+			econtext->ecxt_scantuple = slot;
+			ResetExprContext(econtext);
+			if (!ExecQual(node->indexqual, econtext, false))
+			{
+				/* Fails recheck, so drop it and loop back for another */
+				InstrCountFiltered2(node, 1);
+				continue;
+			}
+		}
+
+		return slot;
+	}
+
+	/*
+	 * if we get here it means the index scan failed so we are at the end of
+	 * the scan..
+	 */
+	return ExecClearTuple(slot);
+}
+
+/*
+ * StoreIndexTuple
+ *		Fill the slot with data from the index tuple.
+ *
+ * At some point this might be generally-useful functionality, but
+ * right now we don't need it elsewhere.
+ */
+static void
+StoreIndexTuple(TupleTableSlot *slot, IndexTuple itup, Relation indexRel)
+{
+	TupleDesc	indexDesc = RelationGetDescr(indexRel);
+	int			nindexatts = indexDesc->natts;
+	Datum	   *values = slot->tts_values;
+	bool	   *isnull = slot->tts_isnull;
+	int			i;
+
+	/*
+	 * Note: we must use the index relation's tupdesc in index_getattr,
+	 * not the slot's tupdesc, because of index_descriptor_hack().
+	 */
+	Assert(slot->tts_tupleDescriptor->natts == nindexatts);
+
+	ExecClearTuple(slot);
+	for (i = 0; i < nindexatts; i++)
+		values[i] = index_getattr(itup, i + 1, indexDesc, &isnull[i]);
+	ExecStoreVirtualTuple(slot);
+}
+
+/*
+ * index_descriptor_hack -- ugly kluge to make index's tupdesc OK for slot
+ *
+ * This is necessary because, alone among btree opclasses, name_ops uses
+ * a storage type (cstring) different from its input type.  The index
+ * tuple descriptor will show "cstring", which is correct, but we have to
+ * expose "name" as the slot datatype or ExecEvalVar will whine.  If we
+ * ever want to have any other cases with a different storage type, we ought
+ * to think of a cleaner solution than this.
+ */
+static TupleDesc
+index_descriptor_hack(Relation indexRel)
+{
+	TupleDesc	tupdesc = RelationGetDescr(indexRel);
+	int			i;
+
+	/* copy so we can scribble on it safely */
+	tupdesc = CreateTupleDescCopy(tupdesc);
+
+	for (i = 0; i < tupdesc->natts; i++)
+	{
+		if (indexRel->rd_opfamily[i] == NAME_BTREE_FAM_OID &&
+			tupdesc->attrs[i]->atttypid == CSTRINGOID)
+		{
+			tupdesc->attrs[i]->atttypid = NAMEOID;
+
+			/*
+			 * We set attlen to match the type OID just in case anything looks
+			 * at it.  Note that this is safe only because StoreIndexTuple
+			 * will insert the data as a virtual tuple, and we don't expect
+			 * anything will try to materialize the scan tuple slot.
+			 */
+			tupdesc->attrs[i]->attlen = NAMEDATALEN;
+		}
+	}
+
+	return tupdesc;
+}
+
+/*
+ * IndexOnlyRecheck -- access method routine to recheck a tuple in EvalPlanQual
+ *
+ * This can't really happen, since an index can't supply CTID which would
+ * be necessary data for any potential EvalPlanQual target relation.  If it
+ * did happen, the EPQ code would pass us the wrong data, namely a heap
+ * tuple not an index tuple.  So throw an error.
+ */
+static bool
+IndexOnlyRecheck(IndexOnlyScanState *node, TupleTableSlot *slot)
+{
+	elog(ERROR, "EvalPlanQual recheck is not supported in index-only scans");
+	return false;				/* keep compiler quiet */
+}
+
+/* ----------------------------------------------------------------
+ *		ExecIndexOnlyScan(node)
+ * ----------------------------------------------------------------
+ */
+TupleTableSlot *
+ExecIndexOnlyScan(IndexOnlyScanState *node)
+{
+	/*
+	 * If we have runtime keys and they've not already been set up, do it now.
+	 */
+	if (node->ioss_NumRuntimeKeys != 0 && !node->ioss_RuntimeKeysReady)
+		ExecReScan((PlanState *) node);
+
+	return ExecScan(&node->ss,
+					(ExecScanAccessMtd) IndexOnlyNext,
+					(ExecScanRecheckMtd) IndexOnlyRecheck);
+}
+
+/* ----------------------------------------------------------------
+ *		ExecReScanIndexOnlyScan(node)
+ *
+ *		Recalculates the values of any scan keys whose value depends on
+ *		information known at runtime, then rescans the indexed relation.
+ *
+ *		Updating the scan key was formerly done separately in
+ *		ExecUpdateIndexScanKeys. Integrating it into ReScan makes
+ *		rescans of indices and relations/general streams more uniform.
+ * ----------------------------------------------------------------
+ */
+void
+ExecReScanIndexOnlyScan(IndexOnlyScanState *node)
+{
+	/*
+	 * If we are doing runtime key calculations (ie, any of the index key
+	 * values weren't simple Consts), compute the new key values.  But first,
+	 * reset the context so we don't leak memory as each outer tuple is
+	 * scanned.  Note this assumes that we will recalculate *all* runtime keys
+	 * on each call.
+	 */
+	if (node->ioss_NumRuntimeKeys != 0)
+	{
+		ExprContext *econtext = node->ioss_RuntimeContext;
+
+		ResetExprContext(econtext);
+		ExecIndexEvalRuntimeKeys(econtext,
+								 node->ioss_RuntimeKeys,
+								 node->ioss_NumRuntimeKeys);
+	}
+	node->ioss_RuntimeKeysReady = true;
+
+	/* reset index scan */
+	index_rescan(node->ioss_ScanDesc,
+				 node->ioss_ScanKeys, node->ioss_NumScanKeys,
+				 node->ioss_OrderByKeys, node->ioss_NumOrderByKeys);
+
+	ExecScanReScan(&node->ss);
+}
+
+
+/* ----------------------------------------------------------------
+ *		ExecEndIndexOnlyScan
+ * ----------------------------------------------------------------
+ */
+void
+ExecEndIndexOnlyScan(IndexOnlyScanState *node)
+{
+	Relation	indexRelationDesc;
+	IndexScanDesc indexScanDesc;
+	Relation	relation;
+
+	/*
+	 * extract information from the node
+	 */
+	indexRelationDesc = node->ioss_RelationDesc;
+	indexScanDesc = node->ioss_ScanDesc;
+	relation = node->ss.ss_currentRelation;
+
+	/* Release VM buffer pin, if any. */
+	if (node->ioss_VMBuffer != InvalidBuffer)
+	{
+		ReleaseBuffer(node->ioss_VMBuffer);
+		node->ioss_VMBuffer = InvalidBuffer;
+	}
+
+	/*
+	 * Free the exprcontext(s) ... now dead code, see ExecFreeExprContext
+	 */
+#ifdef NOT_USED
+	ExecFreeExprContext(&node->ss.ps);
+	if (node->ioss_RuntimeContext)
+		FreeExprContext(node->ioss_RuntimeContext, true);
+#endif
+
+	/*
+	 * clear out tuple table slots
+	 */
+	ExecClearTuple(node->ss.ps.ps_ResultTupleSlot);
+	ExecClearTuple(node->ss.ss_ScanTupleSlot);
+
+	/*
+	 * close the index relation (no-op if we didn't open it)
+	 */
+	if (indexScanDesc)
+		index_endscan(indexScanDesc);
+	if (indexRelationDesc)
+		index_close(indexRelationDesc, NoLock);
+
+	/*
+	 * close the heap relation.
+	 */
+	ExecCloseScanRelation(relation);
+}
+
+/* ----------------------------------------------------------------
+ *		ExecIndexOnlyMarkPos
+ * ----------------------------------------------------------------
+ */
+void
+ExecIndexOnlyMarkPos(IndexOnlyScanState *node)
+{
+	index_markpos(node->ioss_ScanDesc);
+}
+
+/* ----------------------------------------------------------------
+ *		ExecIndexOnlyRestrPos
+ * ----------------------------------------------------------------
+ */
+void
+ExecIndexOnlyRestrPos(IndexOnlyScanState *node)
+{
+	index_restrpos(node->ioss_ScanDesc);
+}
+
+/* ----------------------------------------------------------------
+ *		ExecInitIndexOnlyScan
+ *
+ *		Initializes the index scan's state information, creates
+ *		scan keys, and opens the base and index relations.
+ *
+ *		Note: index scans have 2 sets of state information because
+ *			  we have to keep track of the base relation and the
+ *			  index relation.
+ * ----------------------------------------------------------------
+ */
+IndexOnlyScanState *
+ExecInitIndexOnlyScan(IndexOnlyScan *node, EState *estate, int eflags)
+{
+	IndexOnlyScanState *indexstate;
+	Relation	currentRelation;
+	bool		relistarget;
+	TupleDesc	tupDesc;
+
+	/*
+	 * create state structure
+	 */
+	indexstate = makeNode(IndexOnlyScanState);
+	indexstate->ss.ps.plan = (Plan *) node;
+	indexstate->ss.ps.state = estate;
+
+	/*
+	 * Miscellaneous initialization
+	 *
+	 * create expression context for node
+	 */
+	ExecAssignExprContext(estate, &indexstate->ss.ps);
+
+	indexstate->ss.ps.ps_TupFromTlist = false;
+
+	/*
+	 * initialize child expressions
+	 *
+	 * Note: we don't initialize all of the indexorderby expression, only the
+	 * sub-parts corresponding to runtime keys (see below).
+	 */
+	indexstate->ss.ps.targetlist = (List *)
+		ExecInitExpr((Expr *) node->scan.plan.targetlist,
+					 (PlanState *) indexstate);
+	indexstate->ss.ps.qual = (List *)
+		ExecInitExpr((Expr *) node->scan.plan.qual,
+					 (PlanState *) indexstate);
+	indexstate->indexqual = (List *)
+		ExecInitExpr((Expr *) node->indexqual,
+					 (PlanState *) indexstate);
+
+	/*
+	 * tuple table initialization
+	 */
+	ExecInitResultTupleSlot(estate, &indexstate->ss.ps);
+	ExecInitScanTupleSlot(estate, &indexstate->ss);
+
+	/*
+	 * open the base relation and acquire appropriate lock on it.
+	 */
+	currentRelation = ExecOpenScanRelation(estate, node->scan.scanrelid);
+
+	indexstate->ss.ss_currentRelation = currentRelation;
+	indexstate->ss.ss_currentScanDesc = NULL;	/* no heap scan here */
+
+	/*
+	 * Initialize result tuple type.
+	 */
+	ExecAssignResultTypeFromTL(&indexstate->ss.ps);
+
+	/*
+	 * If we are just doing EXPLAIN (ie, aren't going to run the plan), stop
+	 * here.  This allows an index-advisor plugin to EXPLAIN a plan containing
+	 * references to nonexistent indexes.
+	 */
+	if (eflags & EXEC_FLAG_EXPLAIN_ONLY)
+		return indexstate;
+
+	/*
+	 * Open the index relation.
+	 *
+	 * If the parent table is one of the target relations of the query, then
+	 * InitPlan already opened and write-locked the index, so we can avoid
+	 * taking another lock here.  Otherwise we need a normal reader's lock.
+	 */
+	relistarget = ExecRelationIsTargetRelation(estate, node->scan.scanrelid);
+	indexstate->ioss_RelationDesc = index_open(node->indexid,
+									 relistarget ? NoLock : AccessShareLock);
+
+	/*
+	 * Now we can get the scan tuple's type (which is the index's rowtype,
+	 * not the heap's) and initialize result projection info.
+	 */
+	tupDesc = index_descriptor_hack(indexstate->ioss_RelationDesc);
+	ExecAssignScanType(&indexstate->ss, tupDesc);
+	ExecAssignScanProjectionInfo(&indexstate->ss);
+
+	/*
+	 * Initialize index-specific scan state
+	 */
+	indexstate->ioss_RuntimeKeysReady = false;
+	indexstate->ioss_RuntimeKeys = NULL;
+	indexstate->ioss_NumRuntimeKeys = 0;
+
+	/*
+	 * build the index scan keys from the index qualification
+	 */
+	ExecIndexBuildScanKeys((PlanState *) indexstate,
+						   indexstate->ioss_RelationDesc,
+						   node->indexqual,
+						   false,
+						   &indexstate->ioss_ScanKeys,
+						   &indexstate->ioss_NumScanKeys,
+						   &indexstate->ioss_RuntimeKeys,
+						   &indexstate->ioss_NumRuntimeKeys,
+						   NULL,	/* no ArrayKeys */
+						   NULL);
+
+	/*
+	 * any ORDER BY exprs have to be turned into scankeys in the same way
+	 */
+	ExecIndexBuildScanKeys((PlanState *) indexstate,
+						   indexstate->ioss_RelationDesc,
+						   node->indexorderby,
+						   true,
+						   &indexstate->ioss_OrderByKeys,
+						   &indexstate->ioss_NumOrderByKeys,
+						   &indexstate->ioss_RuntimeKeys,
+						   &indexstate->ioss_NumRuntimeKeys,
+						   NULL,	/* no ArrayKeys */
+						   NULL);
+
+	/*
+	 * If we have runtime keys, we need an ExprContext to evaluate them. The
+	 * node's standard context won't do because we want to reset that context
+	 * for every tuple.  So, build another context just like the other one...
+	 * -tgl 7/11/00
+	 */
+	if (indexstate->ioss_NumRuntimeKeys != 0)
+	{
+		ExprContext *stdecontext = indexstate->ss.ps.ps_ExprContext;
+
+		ExecAssignExprContext(estate, &indexstate->ss.ps);
+		indexstate->ioss_RuntimeContext = indexstate->ss.ps.ps_ExprContext;
+		indexstate->ss.ps.ps_ExprContext = stdecontext;
+	}
+	else
+	{
+		indexstate->ioss_RuntimeContext = NULL;
+	}
+
+	/*
+	 * Initialize scan descriptor.
+	 */
+	indexstate->ioss_ScanDesc = index_beginscan(currentRelation,
+											   indexstate->ioss_RelationDesc,
+											   estate->es_snapshot,
+											   indexstate->ioss_NumScanKeys,
+											 indexstate->ioss_NumOrderByKeys);
+
+	/* Set it up for index-only scan */
+	indexstate->ioss_ScanDesc->xs_want_itup = true;
+	indexstate->ioss_VMBuffer = InvalidBuffer;
+
+	/*
+	 * If no run-time keys to calculate, go ahead and pass the scankeys to the
+	 * index AM.
+	 */
+	if (indexstate->ioss_NumRuntimeKeys == 0)
+		index_rescan(indexstate->ioss_ScanDesc,
+					 indexstate->ioss_ScanKeys,
+					 indexstate->ioss_NumScanKeys,
+					 indexstate->ioss_OrderByKeys,
+					 indexstate->ioss_NumOrderByKeys);
+
+	/*
+	 * all done.
+	 */
+	return indexstate;
+}

src/backend/executor/nodeIndexscan.c

@@ -14,8 +14,8 @@
  */
 /*
  * INTERFACE ROUTINES
- *		ExecIndexScan			scans a relation using indices
+ *		ExecIndexScan			scans a relation using an index
- *		ExecIndexNext			using index to retrieve next tuple
+ *		IndexNext				retrieve next tuple using index
  *		ExecInitIndexScan		creates and initializes state info.
  *		ExecReScanIndexScan		rescans the indexed relation.
  *		ExecEndIndexScan		releases all storage.
@@ -26,7 +26,6 @@
 
 #include "access/nbtree.h"
 #include "access/relscan.h"
-#include "access/visibilitymap.h"
 #include "executor/execdebug.h"
 #include "executor/nodeIndexscan.h"
 #include "optimizer/clauses.h"
@@ -37,7 +36,6 @@
 
 
 static TupleTableSlot *IndexNext(IndexScanState *node);
-static void IndexStoreHeapTuple(TupleTableSlot *slot, IndexScanDesc scandesc);
 
 
 /* ----------------------------------------------------------------
@@ -56,7 +54,6 @@ IndexNext(IndexScanState *node)
 	IndexScanDesc scandesc;
 	HeapTuple	tuple;
 	TupleTableSlot *slot;
-	ItemPointer tid;
 
 	/*
 	 * extract necessary information from index scan node
@@ -76,67 +73,23 @@ IndexNext(IndexScanState *node)
 	slot = node->ss.ss_ScanTupleSlot;
 
 	/*
-	 * OK, now that we have what we need, fetch the next TID.
+	 * ok, now that we have what we need, fetch the next tuple.
 	 */
-	while ((tid = index_getnext_tid(scandesc, direction)) != NULL)
+	while ((tuple = index_getnext(scandesc, direction)) != NULL)
 	{
 		/*
-		 * Attempt index-only scan, if possible.  For this, we need to have
+		 * Store the scanned tuple in the scan tuple slot of the scan state.
-		 * gotten an index tuple from the AM, and we need the TID to reference
+		 * Note: we pass 'false' because tuples returned by amgetnext are
-		 * a heap page on which all tuples are known visible to everybody.
+		 * pointers onto disk pages and must not be pfree()'d.
-		 * If that's the case, we don't need to visit the heap page for tuple
-		 * visibility testing, and we don't need any column values that are
-		 * not available from the index.
-		 *
-		 * Note: in the index-only path, we are still holding pin on the
-		 * scan's xs_cbuf, ie, the previously visited heap page.  It's not
-		 * clear whether it'd be better to release that pin.
 		 */
-		if (scandesc->xs_want_itup &&
+		ExecStoreTuple(tuple,	/* tuple to store */
-			visibilitymap_test(scandesc->heapRelation,
+					   slot,	/* slot to store in */
-							   ItemPointerGetBlockNumber(tid),
+					   scandesc->xs_cbuf,		/* buffer containing tuple */
-							   &node->iss_VMBuffer))
+					   false);	/* don't pfree */
-		{
-			/*
-			 * Convert index tuple to look like a heap tuple, and store the
-			 * results in the scan tuple slot.
-			 */
-			IndexStoreHeapTuple(slot, scandesc);
-		}
-		else
-		{
-			/* Index-only approach not possible, so fetch heap tuple. */
-			tuple = index_fetch_heap(scandesc);
-
-			/* Tuple might not be visible. */
-			if (tuple == NULL)
-				continue;
-
-			/*
-			 * Only MVCC snapshots are supported here, so there should be no
-			 * need to keep following the HOT chain once a visible entry has
-			 * been found.  If we did want to allow that, we'd need to keep
-			 * more state to remember not to call index_getnext_tid next time.
-			 */
-			if (scandesc->xs_continue_hot)
-				elog(ERROR, "unsupported use of non-MVCC snapshot in executor");
-
-			/*
-			 * Store the scanned tuple in the scan tuple slot of the scan
-			 * state.
-			 *
-			 * Note: we pass 'false' because tuples returned by amgetnext are
-			 * pointers onto disk pages and must not be pfree()'d.
-			 */
-			ExecStoreTuple(tuple,	/* tuple to store */
-						   slot,	/* slot to store in */
-						   scandesc->xs_cbuf,	/* buffer containing tuple */
-						   false);	/* don't pfree */
-		}
 
 		/*
 		 * If the index was lossy, we have to recheck the index quals using
-		 * the real tuple.
+		 * the fetched tuple.
 		 */
 		if (scandesc->xs_recheck)
 		{
@@ -160,53 +113,6 @@ IndexNext(IndexScanState *node)
 	return ExecClearTuple(slot);
 }
 
-/*
- * IndexStoreHeapTuple
- *
- *		When performing an index-only scan, we build a faux heap tuple
- *		from the index tuple.  Columns not present in the index are set to
- *		NULL, which is OK because we know they won't be referenced.
- *
- *		The faux tuple is built as a virtual tuple that depends on the
- *		scandesc's xs_itup, so that must remain valid for as long as we
- *		need the slot contents.
- */
-static void
-IndexStoreHeapTuple(TupleTableSlot *slot, IndexScanDesc scandesc)
-{
-	Form_pg_index indexForm = scandesc->indexRelation->rd_index;
-	TupleDesc	indexDesc = RelationGetDescr(scandesc->indexRelation);
-	int			nindexatts = indexDesc->natts;
-	int			nheapatts = slot->tts_tupleDescriptor->natts;
-	Datum	   *values = slot->tts_values;
-	bool	   *isnull = slot->tts_isnull;
-	int			i;
-
-	/* We must first set the slot to empty, and mark all columns as null */
-	ExecClearTuple(slot);
-
-	memset(isnull, true, nheapatts * sizeof(bool));
-
-	/* Transpose index tuple into heap tuple. */
-	for (i = 0; i < nindexatts; i++)
-	{
-		int		indexatt = indexForm->indkey.values[i];
-
-		/* Ignore expression columns, as well as system attributes */
-		if (indexatt <= 0)
-			continue;
-
-		Assert(indexatt <= nheapatts);
-
-		values[indexatt - 1] = index_getattr(scandesc->xs_itup, i + 1,
-											 indexDesc,
-											 &isnull[indexatt - 1]);
-	}
-
-	/* And now we can mark the slot as holding a virtual tuple. */
-	ExecStoreVirtualTuple(slot);
-}
-
 /*
  * IndexRecheck -- access method routine to recheck a tuple in EvalPlanQual
  */
@@ -493,13 +399,6 @@ ExecEndIndexScan(IndexScanState *node)
 	indexScanDesc = node->iss_ScanDesc;
 	relation = node->ss.ss_currentRelation;
 
-	/* Release VM buffer pin, if any. */
-	if (node->iss_VMBuffer != InvalidBuffer)
-	{
-		ReleaseBuffer(node->iss_VMBuffer);
-		node->iss_VMBuffer = InvalidBuffer;
-	}
-
 	/*
 	 * Free the exprcontext(s) ... now dead code, see ExecFreeExprContext
 	 */
@@ -659,7 +558,6 @@ ExecInitIndexScan(IndexScan *node, EState *estate, int eflags)
 	 */
 	ExecIndexBuildScanKeys((PlanState *) indexstate,
 						   indexstate->iss_RelationDesc,
-						   node->scan.scanrelid,
 						   node->indexqual,
 						   false,
 						   &indexstate->iss_ScanKeys,
@@ -674,7 +572,6 @@ ExecInitIndexScan(IndexScan *node, EState *estate, int eflags)
 	 */
 	ExecIndexBuildScanKeys((PlanState *) indexstate,
 						   indexstate->iss_RelationDesc,
-						   node->scan.scanrelid,
 						   node->indexorderby,
 						   true,
 						   &indexstate->iss_OrderByKeys,
@@ -712,10 +609,6 @@ ExecInitIndexScan(IndexScan *node, EState *estate, int eflags)
 											   indexstate->iss_NumScanKeys,
 											 indexstate->iss_NumOrderByKeys);
 
-	/* Prepare for possible index-only scan */
-	indexstate->iss_ScanDesc->xs_want_itup = node->indexonly;
-	indexstate->iss_VMBuffer = InvalidBuffer;
-
 	/*
 	 * If no run-time keys to calculate, go ahead and pass the scankeys to the
 	 * index AM.
@@ -772,7 +665,6 @@ ExecInitIndexScan(IndexScan *node, EState *estate, int eflags)
  *
  * planstate: executor state node we are working for
  * index: the index we are building scan keys for
- * scanrelid: varno of the index's relation within current query
  * quals: indexquals (or indexorderbys) expressions
  * isorderby: true if processing ORDER BY exprs, false if processing quals
  * *runtimeKeys: ptr to pre-existing IndexRuntimeKeyInfos, or NULL if none
@@ -791,7 +683,7 @@ ExecInitIndexScan(IndexScan *node, EState *estate, int eflags)
  * ScalarArrayOpExpr quals are not supported.
  */
 void
-ExecIndexBuildScanKeys(PlanState *planstate, Relation index, Index scanrelid,
+ExecIndexBuildScanKeys(PlanState *planstate, Relation index,
 					   List *quals, bool isorderby,
 					   ScanKey *scanKeys, int *numScanKeys,
 					   IndexRuntimeKeyInfo **runtimeKeys, int *numRuntimeKeys,
@@ -865,7 +757,7 @@ ExecIndexBuildScanKeys(PlanState *planstate, Relation index, Index scanrelid,
 			Assert(leftop != NULL);
 
 			if (!(IsA(leftop, Var) &&
-				  ((Var *) leftop)->varno == scanrelid))
+				  ((Var *) leftop)->varno == INDEX_VAR))
 				elog(ERROR, "indexqual doesn't have key on left side");
 
 			varattno = ((Var *) leftop)->varattno;
@@ -979,7 +871,7 @@ ExecIndexBuildScanKeys(PlanState *planstate, Relation index, Index scanrelid,
 				Assert(leftop != NULL);
 
 				if (!(IsA(leftop, Var) &&
-					  ((Var *) leftop)->varno == scanrelid))
+					  ((Var *) leftop)->varno == INDEX_VAR))
 					elog(ERROR, "indexqual doesn't have key on left side");
 
 				varattno = ((Var *) leftop)->varattno;
@@ -1107,7 +999,7 @@ ExecIndexBuildScanKeys(PlanState *planstate, Relation index, Index scanrelid,
 			Assert(leftop != NULL);
 
 			if (!(IsA(leftop, Var) &&
-				  ((Var *) leftop)->varno == scanrelid))
+				  ((Var *) leftop)->varno == INDEX_VAR))
 				elog(ERROR, "indexqual doesn't have key on left side");
 
 			varattno = ((Var *) leftop)->varattno;
@@ -1172,7 +1064,7 @@ ExecIndexBuildScanKeys(PlanState *planstate, Relation index, Index scanrelid,
 			Assert(leftop != NULL);
 
 			if (!(IsA(leftop, Var) &&
-				  ((Var *) leftop)->varno == scanrelid))
+				  ((Var *) leftop)->varno == INDEX_VAR))
 				elog(ERROR, "NullTest indexqual has wrong key");
 
 			varattno = ((Var *) leftop)->varattno;

src/backend/executor/nodeNestloop.c

@@ -147,8 +147,8 @@ ExecNestLoop(NestLoopState *node)
 				ParamExecData *prm;
 
 				prm = &(econtext->ecxt_param_exec_vals[paramno]);
-				/* Param value should be an OUTER var */
+				/* Param value should be an OUTER_VAR var */
-				Assert(nlp->paramval->varno == OUTER);
+				Assert(nlp->paramval->varno == OUTER_VAR);
 				Assert(nlp->paramval->varattno > 0);
 				prm->value = slot_getattr(outerTupleSlot,
 										  nlp->paramval->varattno,

src/backend/nodes/copyfuncs.c

@@ -370,7 +370,31 @@ _copyIndexScan(IndexScan *from)
 	COPY_NODE_FIELD(indexorderby);
 	COPY_NODE_FIELD(indexorderbyorig);
 	COPY_SCALAR_FIELD(indexorderdir);
-	COPY_SCALAR_FIELD(indexonly);
+
+	return newnode;
+}
+
+/*
+ * _copyIndexOnlyScan
+ */
+static IndexOnlyScan *
+_copyIndexOnlyScan(IndexOnlyScan *from)
+{
+	IndexOnlyScan  *newnode = makeNode(IndexOnlyScan);
+
+	/*
+	 * copy node superclass fields
+	 */
+	CopyScanFields((Scan *) from, (Scan *) newnode);
+
+	/*
+	 * copy remainder of node
+	 */
+	COPY_SCALAR_FIELD(indexid);
+	COPY_NODE_FIELD(indexqual);
+	COPY_NODE_FIELD(indexorderby);
+	COPY_NODE_FIELD(indextlist);
+	COPY_SCALAR_FIELD(indexorderdir);
 
 	return newnode;
 }
@@ -3871,6 +3895,9 @@ copyObject(void *from)
 		case T_IndexScan:
 			retval = _copyIndexScan(from);
 			break;
+		case T_IndexOnlyScan:
+			retval = _copyIndexOnlyScan(from);
+			break;
 		case T_BitmapIndexScan:
 			retval = _copyBitmapIndexScan(from);
 			break;

src/backend/nodes/outfuncs.c

@@ -447,7 +447,20 @@ _outIndexScan(StringInfo str, IndexScan *node)
 	WRITE_NODE_FIELD(indexorderby);
 	WRITE_NODE_FIELD(indexorderbyorig);
 	WRITE_ENUM_FIELD(indexorderdir, ScanDirection);
-	WRITE_BOOL_FIELD(indexonly);
+}
+
+static void
+_outIndexOnlyScan(StringInfo str, IndexOnlyScan *node)
+{
+	WRITE_NODE_TYPE("INDEXONLYSCAN");
+
+	_outScanInfo(str, (Scan *) node);
+
+	WRITE_OID_FIELD(indexid);
+	WRITE_NODE_FIELD(indexqual);
+	WRITE_NODE_FIELD(indexorderby);
+	WRITE_NODE_FIELD(indextlist);
+	WRITE_ENUM_FIELD(indexorderdir, ScanDirection);
 }
 
 static void
@@ -1501,7 +1514,6 @@ _outIndexPath(StringInfo str, IndexPath *node)
 	WRITE_NODE_FIELD(indexorderbys);
 	WRITE_BOOL_FIELD(isjoininner);
 	WRITE_ENUM_FIELD(indexscandir, ScanDirection);
-	WRITE_BOOL_FIELD(indexonly);
 	WRITE_FLOAT_FIELD(indextotalcost, "%.2f");
 	WRITE_FLOAT_FIELD(indexselectivity, "%.4f");
 	WRITE_FLOAT_FIELD(rows, "%.0f");
@@ -1752,8 +1764,9 @@ _outIndexOptInfo(StringInfo str, IndexOptInfo *node)
 	WRITE_FLOAT_FIELD(tuples, "%.0f");
 	WRITE_INT_FIELD(ncolumns);
 	WRITE_OID_FIELD(relam);
-	WRITE_NODE_FIELD(indexprs);
+	/* indexprs is redundant since we print indextlist */
 	WRITE_NODE_FIELD(indpred);
+	WRITE_NODE_FIELD(indextlist);
 	WRITE_BOOL_FIELD(predOK);
 	WRITE_BOOL_FIELD(unique);
 	WRITE_BOOL_FIELD(hypothetical);
@@ -2707,6 +2720,9 @@ _outNode(StringInfo str, void *obj)
 			case T_IndexScan:
 				_outIndexScan(str, obj);
 				break;
+			case T_IndexOnlyScan:
+				_outIndexOnlyScan(str, obj);
+				break;
 			case T_BitmapIndexScan:
 				_outBitmapIndexScan(str, obj);
 				break;

src/backend/nodes/print.c

@@ -320,14 +320,18 @@ print_expr(Node *expr, List *rtable)
 
 		switch (var->varno)
 		{
-			case INNER:
+			case INNER_VAR:
 				relname = "INNER";
 				attname = "?";
 				break;
-			case OUTER:
+			case OUTER_VAR:
 				relname = "OUTER";
 				attname = "?";
 				break;
+			case INDEX_VAR:
+				relname = "INDEX";
+				attname = "?";
+				break;
 			default:
 				{
 					RangeTblEntry *rte;

src/backend/optimizer/path/indxpath.c

@@ -199,14 +199,15 @@ create_index_paths(PlannerInfo *root, RelOptInfo *rel)
 									 true, NULL, SAOP_FORBID, ST_ANYSCAN);
 
 	/*
-	 * Submit all the ones that can form plain IndexScan plans to add_path. (A
+	 * Submit all the ones that can form plain IndexScan plans to add_path.
-	 * plain IndexPath always represents a plain IndexScan plan; however some
+	 * (A plain IndexPath might represent either a plain IndexScan or an
-	 * of the indexes might support only bitmap scans, and those we mustn't
+	 * IndexOnlyScan, but for our purposes here the distinction does not
-	 * submit to add_path here.)  Also, pick out the ones that might be useful
+	 * matter.  However, some of the indexes might support only bitmap scans,
-	 * as bitmap scans.  For that, we must discard indexes that don't support
+	 * and those we mustn't submit to add_path here.)  Also, pick out the ones
-	 * bitmap scans, and we also are only interested in paths that have some
+	 * that might be useful as bitmap scans.  For that, we must discard
-	 * selectivity; we should discard anything that was generated solely for
+	 * indexes that don't support bitmap scans, and we also are only
-	 * ordering purposes.
+	 * interested in paths that have some selectivity; we should discard
+	 * anything that was generated solely for ordering purposes.
 	 */
 	bitindexpaths = NIL;
 	foreach(l, indexpaths)
@@ -1107,11 +1108,9 @@ check_index_only(RelOptInfo *rel, IndexOptInfo *index)
 
 		/*
 		 * For the moment, we just ignore index expressions.  It might be nice
-		 * to do something with them, later.  We also ignore index columns
+		 * to do something with them, later.
-		 * that are system columns (such as OID), because the virtual-tuple
-		 * coding used by IndexStoreHeapTuple() can't deal with them.
 		 */
-		if (attno <= 0)
+		if (attno == 0)
 			continue;
 
 		index_attrs =

src/backend/optimizer/path/pathkeys.c

@@ -25,7 +25,6 @@
 #include "optimizer/pathnode.h"
 #include "optimizer/paths.h"
 #include "optimizer/tlist.h"
-#include "parser/parsetree.h"
 #include "utils/lsyscache.h"
 
 
@@ -35,8 +34,6 @@ static PathKey *make_canonical_pathkey(PlannerInfo *root,
 					   EquivalenceClass *eclass, Oid opfamily,
 					   int strategy, bool nulls_first);
 static bool pathkey_is_redundant(PathKey *new_pathkey, List *pathkeys);
-static Var *find_indexkey_var(PlannerInfo *root, RelOptInfo *rel,
-				  AttrNumber varattno);
 static bool right_merge_direction(PlannerInfo *root, PathKey *pathkey);
 
 
@@ -504,21 +501,24 @@ build_index_pathkeys(PlannerInfo *root,
 					 ScanDirection scandir)
 {
 	List	   *retval = NIL;
-	ListCell   *indexprs_item;
+	ListCell   *lc;
 	int			i;
 
 	if (index->sortopfamily == NULL)
 		return NIL;				/* non-orderable index */
 
-	indexprs_item = list_head(index->indexprs);
+	i = 0;
-	for (i = 0; i < index->ncolumns; i++)
+	foreach(lc, index->indextlist)
 	{
+		TargetEntry *indextle = (TargetEntry *) lfirst(lc);
+		Expr	   *indexkey;
 		bool		reverse_sort;
 		bool		nulls_first;
-		int			ikey;
-		Expr	   *indexkey;
 		PathKey    *cpathkey;
 
+		/* We assume we don't need to make a copy of the tlist item */
+		indexkey = indextle->expr;
+
 		if (ScanDirectionIsBackward(scandir))
 		{
 			reverse_sort = !index->reverse_sort[i];
@@ -530,21 +530,6 @@ build_index_pathkeys(PlannerInfo *root,
 			nulls_first = index->nulls_first[i];
 		}
 
-		ikey = index->indexkeys[i];
-		if (ikey != 0)
-		{
-			/* simple index column */
-			indexkey = (Expr *) find_indexkey_var(root, index->rel, ikey);
-		}
-		else
-		{
-			/* expression --- assume we need not copy it */
-			if (indexprs_item == NULL)
-				elog(ERROR, "wrong number of index expressions");
-			indexkey = (Expr *) lfirst(indexprs_item);
-			indexprs_item = lnext(indexprs_item);
-		}
-
 		/* OK, try to make a canonical pathkey for this sort key */
 		cpathkey = make_pathkey_from_sortinfo(root,
 											  indexkey,
@@ -568,46 +553,13 @@ build_index_pathkeys(PlannerInfo *root,
 		/* Add to list unless redundant */
 		if (!pathkey_is_redundant(cpathkey, retval))
 			retval = lappend(retval, cpathkey);
+
+		i++;
 	}
 
 	return retval;
 }
 
-/*
- * Find or make a Var node for the specified attribute of the rel.
- *
- * We first look for the var in the rel's target list, because that's
- * easy and fast.  But the var might not be there (this should normally
- * only happen for vars that are used in WHERE restriction clauses,
- * but not in join clauses or in the SELECT target list).  In that case,
- * gin up a Var node the hard way.
- */
-static Var *
-find_indexkey_var(PlannerInfo *root, RelOptInfo *rel, AttrNumber varattno)
-{
-	ListCell   *temp;
-	Index		relid;
-	Oid			reloid,
-				vartypeid,
-				varcollid;
-	int32		type_mod;
-
-	foreach(temp, rel->reltargetlist)
-	{
-		Var		   *var = (Var *) lfirst(temp);
-
-		if (IsA(var, Var) &&
-			var->varattno == varattno)
-			return var;
-	}
-
-	relid = rel->relid;
-	reloid = getrelid(relid, root->parse->rtable);
-	get_atttypetypmodcoll(reloid, varattno, &vartypeid, &type_mod, &varcollid);
-
-	return makeVar(relid, varattno, vartypeid, type_mod, varcollid, 0);
-}
-
 /*
  * convert_subquery_pathkeys
  *	  Build a pathkeys list that describes the ordering of a subquery's

src/backend/optimizer/plan/createplan.c

@@ -53,8 +53,8 @@ static Material *create_material_plan(PlannerInfo *root, MaterialPath *best_path
 static Plan *create_unique_plan(PlannerInfo *root, UniquePath *best_path);
 static SeqScan *create_seqscan_plan(PlannerInfo *root, Path *best_path,
 					List *tlist, List *scan_clauses);
-static IndexScan *create_indexscan_plan(PlannerInfo *root, IndexPath *best_path,
+static Scan *create_indexscan_plan(PlannerInfo *root, IndexPath *best_path,
-					  List *tlist, List *scan_clauses);
+					  List *tlist, List *scan_clauses, bool indexonly);
 static BitmapHeapScan *create_bitmap_scan_plan(PlannerInfo *root,
 						BitmapHeapPath *best_path,
 						List *tlist, List *scan_clauses);
@@ -95,7 +95,12 @@ static SeqScan *make_seqscan(List *qptlist, List *qpqual, Index scanrelid);
 static IndexScan *make_indexscan(List *qptlist, List *qpqual, Index scanrelid,
 			   Oid indexid, List *indexqual, List *indexqualorig,
 			   List *indexorderby, List *indexorderbyorig,
-			   ScanDirection indexscandir, bool indexonly);
+			   ScanDirection indexscandir);
+static IndexOnlyScan *make_indexonlyscan(List *qptlist, List *qpqual,
+				   Index scanrelid, Oid indexid,
+				   List *indexqual, List *indexorderby,
+				   List *indextlist,
+				   ScanDirection indexscandir);
 static BitmapIndexScan *make_bitmap_indexscan(Index scanrelid, Oid indexid,
 					  List *indexqual,
 					  List *indexqualorig);
@@ -206,6 +211,7 @@ create_plan_recurse(PlannerInfo *root, Path *best_path)
 	{
 		case T_SeqScan:
 		case T_IndexScan:
+		case T_IndexOnlyScan:
 		case T_BitmapHeapScan:
 		case T_TidScan:
 		case T_SubqueryScan:
@@ -274,10 +280,18 @@ create_scan_plan(PlannerInfo *root, Path *best_path)
 	 */
 	if (use_physical_tlist(root, rel))
 	{
-		tlist = build_physical_tlist(root, rel);
+		if (best_path->pathtype == T_IndexOnlyScan)
-		/* if fail because of dropped cols, use regular method */
+		{
-		if (tlist == NIL)
+			/* For index-only scan, the preferred tlist is the index's */
-			tlist = build_relation_tlist(rel);
+			tlist = copyObject(((IndexPath *) best_path)->indexinfo->indextlist);
+		}
+		else
+		{
+			tlist = build_physical_tlist(root, rel);
+			/* if fail because of dropped cols, use regular method */
+			if (tlist == NIL)
+				tlist = build_relation_tlist(rel);
+		}
 	}
 	else
 		tlist = build_relation_tlist(rel);
@@ -302,7 +316,16 @@ create_scan_plan(PlannerInfo *root, Path *best_path)
 			plan = (Plan *) create_indexscan_plan(root,
 												  (IndexPath *) best_path,
 												  tlist,
-												  scan_clauses);
+												  scan_clauses,
+												  false);
+			break;
+
+		case T_IndexOnlyScan:
+			plan = (Plan *) create_indexscan_plan(root,
+												  (IndexPath *) best_path,
+												  tlist,
+												  scan_clauses,
+												  true);
 			break;
 
 		case T_BitmapHeapScan:
@@ -476,6 +499,7 @@ disuse_physical_tlist(Plan *plan, Path *path)
 	{
 		case T_SeqScan:
 		case T_IndexScan:
+		case T_IndexOnlyScan:
 		case T_BitmapHeapScan:
 		case T_TidScan:
 		case T_SubqueryScan:
@@ -1044,16 +1068,23 @@ create_seqscan_plan(PlannerInfo *root, Path *best_path,
  *	  Returns an indexscan plan for the base relation scanned by 'best_path'
  *	  with restriction clauses 'scan_clauses' and targetlist 'tlist'.
  *
+ * We use this for both plain IndexScans and IndexOnlyScans, because the
+ * qual preprocessing work is the same for both.  Note that the caller tells
+ * us which to build --- we don't look at best_path->path.pathtype, because
+ * create_bitmap_subplan needs to be able to override the prior decision.
+ *
  * The indexquals list of the path contains implicitly-ANDed qual conditions.
  * The list can be empty --- then no index restrictions will be applied during
  * the scan.
  */
-static IndexScan *
+static Scan *
 create_indexscan_plan(PlannerInfo *root,
 					  IndexPath *best_path,
 					  List *tlist,
-					  List *scan_clauses)
+					  List *scan_clauses,
+					  bool indexonly)
 {
+	Scan	   *scan_plan;
 	List	   *indexquals = best_path->indexquals;
 	List	   *indexorderbys = best_path->indexorderbys;
 	Index		baserelid = best_path->path.parent->relid;
@@ -1063,7 +1094,6 @@ create_indexscan_plan(PlannerInfo *root,
 	List	   *fixed_indexquals;
 	List	   *fixed_indexorderbys;
 	ListCell   *l;
-	IndexScan  *scan_plan;
 
 	/* it should be a base rel... */
 	Assert(baserelid > 0);
@@ -1077,7 +1107,7 @@ create_indexscan_plan(PlannerInfo *root,
 
 	/*
 	 * The executor needs a copy with the indexkey on the left of each clause
-	 * and with index attr numbers substituted for table ones.
+	 * and with index Vars substituted for table ones.
 	 */
 	fixed_indexquals = fix_indexqual_references(root, best_path, indexquals);
 
@@ -1175,20 +1205,29 @@ create_indexscan_plan(PlannerInfo *root,
 	}
 
 	/* Finally ready to build the plan node */
-	scan_plan = make_indexscan(tlist,
+	if (indexonly)
-							   qpqual,
+		scan_plan = (Scan *) make_indexonlyscan(tlist,
-							   baserelid,
+												qpqual,
-							   indexoid,
+												baserelid,
-							   fixed_indexquals,
+												indexoid,
-							   stripped_indexquals,
+												fixed_indexquals,
-							   fixed_indexorderbys,
+												fixed_indexorderbys,
-							   indexorderbys,
+												best_path->indexinfo->indextlist,
-							   best_path->indexscandir,
+												best_path->indexscandir);
-							   best_path->indexonly);
+	else
+		scan_plan = (Scan *) make_indexscan(tlist,
+											qpqual,
+											baserelid,
+											indexoid,
+											fixed_indexquals,
+											stripped_indexquals,
+											fixed_indexorderbys,
+											indexorderbys,
+											best_path->indexscandir);
 
-	copy_path_costsize(&scan_plan->scan.plan, &best_path->path);
+	copy_path_costsize(&scan_plan->plan, &best_path->path);
 	/* use the indexscan-specific rows estimate, not the parent rel's */
-	scan_plan->scan.plan.plan_rows = best_path->rows;
+	scan_plan->plan.plan_rows = best_path->rows;
 
 	return scan_plan;
 }
@@ -1440,7 +1479,9 @@ create_bitmap_subplan(PlannerInfo *root, Path *bitmapqual,
 		ListCell   *l;
 
 		/* Use the regular indexscan plan build machinery... */
-		iscan = create_indexscan_plan(root, ipath, NIL, NIL);
+		iscan = (IndexScan *) create_indexscan_plan(root, ipath,
+													NIL, NIL, false);
+		Assert(IsA(iscan, IndexScan));
 		/* then convert to a bitmap indexscan */
 		plan = (Plan *) make_bitmap_indexscan(iscan->scan.scanrelid,
 											  iscan->indexid,
@@ -2549,17 +2590,13 @@ fix_indexorderby_references(PlannerInfo *root, IndexPath *index_path,
 /*
  * fix_indexqual_operand
  *	  Convert an indexqual expression to a Var referencing the index column.
+ *
+ * We represent index keys by Var nodes having varno == INDEX_VAR and varattno
+ * equal to the index's attribute number (index column position).
  */
 static Node *
 fix_indexqual_operand(Node *node, IndexOptInfo *index)
 {
-	/*
-	 * We represent index keys by Var nodes having the varno of the base table
-	 * but varattno equal to the index's attribute number (index column
-	 * position).  This is a bit hokey ... would be cleaner to use a
-	 * special-purpose node type that could not be mistaken for a regular Var.
-	 * But it will do for now.
-	 */
 	Var		   *result;
 	int			pos;
 	ListCell   *indexpr_item;
@@ -2583,6 +2620,7 @@ fix_indexqual_operand(Node *node, IndexOptInfo *index)
 				if (index->indexkeys[pos] == varatt)
 				{
 					result = (Var *) copyObject(node);
+					result->varno = INDEX_VAR;
 					result->varattno = pos + 1;
 					return (Node *) result;
 				}
@@ -2606,7 +2644,7 @@ fix_indexqual_operand(Node *node, IndexOptInfo *index)
 			if (equal(node, indexkey))
 			{
 				/* Found a match */
-				result = makeVar(index->rel->relid, pos + 1,
+				result = makeVar(INDEX_VAR, pos + 1,
 								 exprType(lfirst(indexpr_item)), -1,
 								 exprCollation(lfirst(indexpr_item)),
 								 0);
@@ -2842,8 +2880,7 @@ make_indexscan(List *qptlist,
 			   List *indexqualorig,
 			   List *indexorderby,
 			   List *indexorderbyorig,
-			   ScanDirection indexscandir,
+			   ScanDirection indexscandir)
-			   bool indexonly)
 {
 	IndexScan  *node = makeNode(IndexScan);
 	Plan	   *plan = &node->scan.plan;
@@ -2860,7 +2897,34 @@ make_indexscan(List *qptlist,
 	node->indexorderby = indexorderby;
 	node->indexorderbyorig = indexorderbyorig;
 	node->indexorderdir = indexscandir;
-	node->indexonly = indexonly;
+
+	return node;
+}
+
+static IndexOnlyScan *
+make_indexonlyscan(List *qptlist,
+				   List *qpqual,
+				   Index scanrelid,
+				   Oid indexid,
+				   List *indexqual,
+				   List *indexorderby,
+				   List *indextlist,
+				   ScanDirection indexscandir)
+{
+	IndexOnlyScan *node = makeNode(IndexOnlyScan);
+	Plan	   *plan = &node->scan.plan;
+
+	/* cost should be inserted by caller */
+	plan->targetlist = qptlist;
+	plan->qual = qpqual;
+	plan->lefttree = NULL;
+	plan->righttree = NULL;
+	node->scan.scanrelid = scanrelid;
+	node->indexid = indexid;
+	node->indexqual = indexqual;
+	node->indexorderby = indexorderby;
+	node->indextlist = indextlist;
+	node->indexorderdir = indexscandir;
 
 	return node;
 }

src/backend/optimizer/plan/setrefs.c

@@ -63,6 +63,7 @@ typedef struct
 {
 	PlannerInfo *root;
 	indexed_tlist *subplan_itlist;
+	Index		newvarno;
 	int			rtoffset;
 } fix_upper_expr_context;
 
@@ -81,6 +82,9 @@ typedef struct
 	((List *) fix_scan_expr(root, (Node *) (lst), rtoffset))
 
 static Plan *set_plan_refs(PlannerInfo *root, Plan *plan, int rtoffset);
+static Plan *set_indexonlyscan_references(PlannerInfo *root,
+							 IndexOnlyScan *plan,
+							 int rtoffset);
 static Plan *set_subqueryscan_references(PlannerInfo *root,
 							SubqueryScan *plan,
 							int rtoffset);
@@ -113,6 +117,7 @@ static Node *fix_join_expr_mutator(Node *node,
 static Node *fix_upper_expr(PlannerInfo *root,
 			   Node *node,
 			   indexed_tlist *subplan_itlist,
+			   Index newvarno,
 			   int rtoffset);
 static Node *fix_upper_expr_mutator(Node *node,
 					   fix_upper_expr_context *context);
@@ -234,6 +239,16 @@ set_plan_references(PlannerInfo *root, Plan *plan)
 											 newrte->relid);
 	}
 
+	/*
+	 * Check for RT index overflow; it's very unlikely, but if it did happen,
+	 * the executor would get confused by varnos that match the special varno
+	 * values.
+	 */
+	if (IS_SPECIAL_VARNO(list_length(glob->finalrtable)))
+		ereport(ERROR,
+				(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
+				 errmsg("too many range table entries")));
+
 	/*
 	 * Adjust RT indexes of PlanRowMarks and add to final rowmarks list
 	 */
@@ -305,6 +320,13 @@ set_plan_refs(PlannerInfo *root, Plan *plan, int rtoffset)
 					fix_scan_list(root, splan->indexorderbyorig, rtoffset);
 			}
 			break;
+		case T_IndexOnlyScan:
+			{
+				IndexOnlyScan  *splan = (IndexOnlyScan *) plan;
+
+				return set_indexonlyscan_references(root, splan, rtoffset);
+			}
+			break;
 		case T_BitmapIndexScan:
 			{
 				BitmapIndexScan *splan = (BitmapIndexScan *) plan;
@@ -652,6 +674,49 @@ set_plan_refs(PlannerInfo *root, Plan *plan, int rtoffset)
 	return plan;
 }
 
+/*
+ * set_indexonlyscan_references
+ *		Do set_plan_references processing on an IndexOnlyScan
+ *
+ * This is unlike the handling of a plain IndexScan because we have to
+ * convert Vars referencing the heap into Vars referencing the index.
+ * We can use the fix_upper_expr machinery for that, by working from a
+ * targetlist describing the index columns.
+ */
+static Plan *
+set_indexonlyscan_references(PlannerInfo *root,
+							 IndexOnlyScan *plan,
+							 int rtoffset)
+{
+	indexed_tlist *index_itlist;
+
+	index_itlist = build_tlist_index(plan->indextlist);
+
+	plan->scan.scanrelid += rtoffset;
+	plan->scan.plan.targetlist = (List *)
+		fix_upper_expr(root,
+					   (Node *) plan->scan.plan.targetlist,
+					   index_itlist,
+					   INDEX_VAR,
+					   rtoffset);
+	plan->scan.plan.qual = (List *)
+		fix_upper_expr(root,
+					   (Node *) plan->scan.plan.qual,
+					   index_itlist,
+					   INDEX_VAR,
+					   rtoffset);
+	/* indexqual is already transformed to reference index columns */
+	plan->indexqual = fix_scan_list(root, plan->indexqual, rtoffset);
+	/* indexorderby is already transformed to reference index columns */
+	plan->indexorderby = fix_scan_list(root, plan->indexorderby, rtoffset);
+	/* indextlist must NOT be transformed to reference index columns */
+	plan->indextlist = fix_scan_list(root, plan->indextlist, rtoffset);
+
+	pfree(index_itlist);
+
+	return (Plan *) plan;
+}
+
 /*
  * set_subqueryscan_references
  *		Do set_plan_references processing on a SubqueryScan
@@ -919,11 +984,13 @@ fix_scan_expr_mutator(Node *node, fix_scan_expr_context *context)
 		Assert(var->varlevelsup == 0);
 
 		/*
-		 * We should not see any Vars marked INNER or OUTER.
+		 * We should not see any Vars marked INNER_VAR or OUTER_VAR.  But an
+		 * indexqual expression could contain INDEX_VAR Vars.
 		 */
-		Assert(var->varno != INNER);
+		Assert(var->varno != INNER_VAR);
-		Assert(var->varno != OUTER);
+		Assert(var->varno != OUTER_VAR);
-		var->varno += context->rtoffset;
+		if (!IS_SPECIAL_VARNO(var->varno))
+			var->varno += context->rtoffset;
 		if (var->varnoold > 0)
 			var->varnoold += context->rtoffset;
 		return (Node *) var;
@@ -932,9 +999,10 @@ fix_scan_expr_mutator(Node *node, fix_scan_expr_context *context)
 	{
 		CurrentOfExpr *cexpr = (CurrentOfExpr *) copyObject(node);
 
-		Assert(cexpr->cvarno != INNER);
+		Assert(cexpr->cvarno != INNER_VAR);
-		Assert(cexpr->cvarno != OUTER);
+		Assert(cexpr->cvarno != OUTER_VAR);
-		cexpr->cvarno += context->rtoffset;
+		if (!IS_SPECIAL_VARNO(cexpr->cvarno))
+			cexpr->cvarno += context->rtoffset;
 		return (Node *) cexpr;
 	}
 	if (IsA(node, PlaceHolderVar))
@@ -963,9 +1031,9 @@ fix_scan_expr_walker(Node *node, fix_scan_expr_context *context)
 /*
  * set_join_references
  *	  Modify the target list and quals of a join node to reference its
- *	  subplans, by setting the varnos to OUTER or INNER and setting attno
+ *	  subplans, by setting the varnos to OUTER_VAR or INNER_VAR and setting
- *	  values to the result domain number of either the corresponding outer
+ *	  attno values to the result domain number of either the corresponding
- *	  or inner join tuple item.  Also perform opcode lookup for these
+ *	  outer or inner join tuple item.  Also perform opcode lookup for these
  *	  expressions. and add regclass OIDs to root->glob->relationOids.
  */
 static void
@@ -1012,6 +1080,7 @@ set_join_references(PlannerInfo *root, Join *join, int rtoffset)
 			nlp->paramval = (Var *) fix_upper_expr(root,
 												   (Node *) nlp->paramval,
 												   outer_itlist,
+												   OUTER_VAR,
 												   rtoffset);
 		}
 	}
@@ -1083,17 +1152,19 @@ set_upper_references(PlannerInfo *root, Plan *plan, int rtoffset)
 				search_indexed_tlist_for_sortgroupref((Node *) tle->expr,
 													  tle->ressortgroupref,
 													  subplan_itlist,
-													  OUTER);
+													  OUTER_VAR);
 			if (!newexpr)
 				newexpr = fix_upper_expr(root,
 										 (Node *) tle->expr,
 										 subplan_itlist,
+										 OUTER_VAR,
 										 rtoffset);
 		}
 		else
 			newexpr = fix_upper_expr(root,
 									 (Node *) tle->expr,
 									 subplan_itlist,
+									 OUTER_VAR,
 									 rtoffset);
 		tle = flatCopyTargetEntry(tle);
 		tle->expr = (Expr *) newexpr;
@@ -1105,6 +1176,7 @@ set_upper_references(PlannerInfo *root, Plan *plan, int rtoffset)
 		fix_upper_expr(root,
 					   (Node *) plan->qual,
 					   subplan_itlist,
+					   OUTER_VAR,
 					   rtoffset);
 
 	pfree(subplan_itlist);
@@ -1113,7 +1185,7 @@ set_upper_references(PlannerInfo *root, Plan *plan, int rtoffset)
 /*
  * set_dummy_tlist_references
  *	  Replace the targetlist of an upper-level plan node with a simple
- *	  list of OUTER references to its child.
+ *	  list of OUTER_VAR references to its child.
  *
  * This is used for plan types like Sort and Append that don't evaluate
  * their targetlists.  Although the executor doesn't care at all what's in
@@ -1136,7 +1208,7 @@ set_dummy_tlist_references(Plan *plan, int rtoffset)
 		Var		   *oldvar = (Var *) tle->expr;
 		Var		   *newvar;
 
-		newvar = makeVar(OUTER,
+		newvar = makeVar(OUTER_VAR,
 						 tle->resno,
 						 exprType((Node *) oldvar),
 						 exprTypmod((Node *) oldvar),
@@ -1382,11 +1454,12 @@ search_indexed_tlist_for_sortgroupref(Node *node,
  *	   relation target lists.  Also perform opcode lookup and add
  *	   regclass OIDs to root->glob->relationOids.
  *
- * This is used in two different scenarios: a normal join clause, where
+ * This is used in two different scenarios: a normal join clause, where all
- * all the Vars in the clause *must* be replaced by OUTER or INNER references;
+ * the Vars in the clause *must* be replaced by OUTER_VAR or INNER_VAR
- * and a RETURNING clause, which may contain both Vars of the target relation
+ * references; and a RETURNING clause, which may contain both Vars of the
- * and Vars of other relations.  In the latter case we want to replace the
+ * target relation and Vars of other relations.  In the latter case we want
- * other-relation Vars by OUTER references, while leaving target Vars alone.
+ * to replace the other-relation Vars by OUTER_VAR references, while leaving
+ * target Vars alone.
  *
  * For a normal join, acceptable_rel should be zero so that any failure to
  * match a Var will be reported as an error.  For the RETURNING case, pass
@@ -1435,7 +1508,7 @@ fix_join_expr_mutator(Node *node, fix_join_expr_context *context)
 		/* First look for the var in the input tlists */
 		newvar = search_indexed_tlist_for_var(var,
 											  context->outer_itlist,
-											  OUTER,
+											  OUTER_VAR,
 											  context->rtoffset);
 		if (newvar)
 			return (Node *) newvar;
@@ -1443,7 +1516,7 @@ fix_join_expr_mutator(Node *node, fix_join_expr_context *context)
 		{
 			newvar = search_indexed_tlist_for_var(var,
 												  context->inner_itlist,
-												  INNER,
+												  INNER_VAR,
 												  context->rtoffset);
 			if (newvar)
 				return (Node *) newvar;
@@ -1470,7 +1543,7 @@ fix_join_expr_mutator(Node *node, fix_join_expr_context *context)
 		{
 			newvar = search_indexed_tlist_for_non_var((Node *) phv,
 													  context->outer_itlist,
-													  OUTER);
+													  OUTER_VAR);
 			if (newvar)
 				return (Node *) newvar;
 		}
@@ -1478,7 +1551,7 @@ fix_join_expr_mutator(Node *node, fix_join_expr_context *context)
 		{
 			newvar = search_indexed_tlist_for_non_var((Node *) phv,
 													  context->inner_itlist,
-													  INNER);
+													  INNER_VAR);
 			if (newvar)
 				return (Node *) newvar;
 		}
@@ -1491,7 +1564,7 @@ fix_join_expr_mutator(Node *node, fix_join_expr_context *context)
 	{
 		newvar = search_indexed_tlist_for_non_var(node,
 												  context->outer_itlist,
-												  OUTER);
+												  OUTER_VAR);
 		if (newvar)
 			return (Node *) newvar;
 	}
@@ -1499,7 +1572,7 @@ fix_join_expr_mutator(Node *node, fix_join_expr_context *context)
 	{
 		newvar = search_indexed_tlist_for_non_var(node,
 												  context->inner_itlist,
-												  INNER);
+												  INNER_VAR);
 		if (newvar)
 			return (Node *) newvar;
 	}
@@ -1516,7 +1589,7 @@ fix_join_expr_mutator(Node *node, fix_join_expr_context *context)
  *		root->glob->relationOids.
  *
  * This is used to fix up target and qual expressions of non-join upper-level
- * plan nodes.
+ * plan nodes, as well as index-only scan nodes.
  *
  * An error is raised if no matching var can be found in the subplan tlist
  * --- so this routine should only be applied to nodes whose subplans'
@@ -1529,23 +1602,26 @@ fix_join_expr_mutator(Node *node, fix_join_expr_context *context)
  * subplan tlist is just a flattened list of Vars.)
  *
  * 'node': the tree to be fixed (a target item or qual)
- * 'subplan_itlist': indexed target list for subplan
+ * 'subplan_itlist': indexed target list for subplan (or index)
+ * 'newvarno': varno to use for Vars referencing tlist elements
  * 'rtoffset': how much to increment varnoold by
  *
  * The resulting tree is a copy of the original in which all Var nodes have
- * varno = OUTER, varattno = resno of corresponding subplan target.
+ * varno = newvarno, varattno = resno of corresponding targetlist element.
  * The original tree is not modified.
  */
 static Node *
 fix_upper_expr(PlannerInfo *root,
 			   Node *node,
 			   indexed_tlist *subplan_itlist,
+			   Index newvarno,
 			   int rtoffset)
 {
 	fix_upper_expr_context context;
 
 	context.root = root;
 	context.subplan_itlist = subplan_itlist;
+	context.newvarno = newvarno;
 	context.rtoffset = rtoffset;
 	return fix_upper_expr_mutator(node, &context);
 }
@@ -1563,7 +1639,7 @@ fix_upper_expr_mutator(Node *node, fix_upper_expr_context *context)
 
 		newvar = search_indexed_tlist_for_var(var,
 											  context->subplan_itlist,
-											  OUTER,
+											  context->newvarno,
 											  context->rtoffset);
 		if (!newvar)
 			elog(ERROR, "variable not found in subplan target list");
@@ -1578,7 +1654,7 @@ fix_upper_expr_mutator(Node *node, fix_upper_expr_context *context)
 		{
 			newvar = search_indexed_tlist_for_non_var((Node *) phv,
 													  context->subplan_itlist,
-													  OUTER);
+													  context->newvarno);
 			if (newvar)
 				return (Node *) newvar;
 		}
@@ -1590,7 +1666,7 @@ fix_upper_expr_mutator(Node *node, fix_upper_expr_context *context)
 	{
 		newvar = search_indexed_tlist_for_non_var(node,
 												  context->subplan_itlist,
-												  OUTER);
+												  context->newvarno);
 		if (newvar)
 			return (Node *) newvar;
 	}
@@ -1610,7 +1686,7 @@ fix_upper_expr_mutator(Node *node, fix_upper_expr_context *context)
  * table should be left alone, however (the executor will evaluate them
  * using the actual heap tuple, after firing triggers if any).	In the
  * adjusted RETURNING list, result-table Vars will still have their
- * original varno, but Vars for other rels will have varno OUTER.
+ * original varno, but Vars for other rels will have varno OUTER_VAR.
  *
  * We also must perform opcode lookup and add regclass OIDs to
  * root->glob->relationOids.

src/backend/optimizer/plan/subselect.c

@@ -1974,6 +1974,18 @@ finalize_plan(PlannerInfo *root, Plan *plan, Bitmapset *valid_params,
 			context.paramids = bms_add_members(context.paramids, scan_params);
 			break;
 
+		case T_IndexOnlyScan:
+			finalize_primnode((Node *) ((IndexOnlyScan *) plan)->indexqual,
+							  &context);
+			finalize_primnode((Node *) ((IndexOnlyScan *) plan)->indexorderby,
+							  &context);
+
+			/*
+			 * we need not look at indextlist, since it cannot contain Params.
+			 */
+			context.paramids = bms_add_members(context.paramids, scan_params);
+			break;
+
 		case T_BitmapIndexScan:
 			finalize_primnode((Node *) ((BitmapIndexScan *) plan)->indexqual,
 							  &context);

src/backend/optimizer/util/pathnode.c

@@ -452,7 +452,7 @@ create_index_path(PlannerInfo *root,
 		indexscandir = NoMovementScanDirection;
 	}
 
-	pathnode->path.pathtype = T_IndexScan;
+	pathnode->path.pathtype = indexonly ? T_IndexOnlyScan : T_IndexScan;
 	pathnode->path.parent = rel;
 	pathnode->path.pathkeys = pathkeys;
 
@@ -470,7 +470,6 @@ create_index_path(PlannerInfo *root,
 
 	pathnode->isjoininner = (outer_rel != NULL);
 	pathnode->indexscandir = indexscandir;
-	pathnode->indexonly = indexonly;
 
 	if (outer_rel != NULL)
 	{

src/backend/optimizer/util/plancat.c

@@ -22,6 +22,7 @@
 #include "access/sysattr.h"
 #include "access/transam.h"
 #include "catalog/catalog.h"
+#include "catalog/heap.h"
 #include "miscadmin.h"
 #include "nodes/makefuncs.h"
 #include "optimizer/clauses.h"
@@ -49,6 +50,8 @@ static int32 get_rel_data_width(Relation rel, int32 *attr_widths);
 static List *get_relation_constraints(PlannerInfo *root,
 						 Oid relationObjectId, RelOptInfo *rel,
 						 bool include_notnull);
+static List *build_index_tlist(PlannerInfo *root, IndexOptInfo *index,
+				  Relation heapRelation);
 
 
 /*
@@ -314,6 +317,10 @@ get_relation_info(PlannerInfo *root, Oid relationObjectId, bool inhparent,
 				ChangeVarNodes((Node *) info->indexprs, 1, varno, 0);
 			if (info->indpred && varno != 1)
 				ChangeVarNodes((Node *) info->indpred, 1, varno, 0);
+
+			/* Build targetlist using the completed indexprs data */
+			info->indextlist = build_index_tlist(root, info, relation);
+
 			info->predOK = false;		/* set later in indxpath.c */
 			info->unique = index->indisunique;
 			info->hypothetical = false;
@@ -900,6 +907,70 @@ build_physical_tlist(PlannerInfo *root, RelOptInfo *rel)
 	return tlist;
 }
 
+/*
+ * build_index_tlist
+ *
+ * Build a targetlist representing the columns of the specified index.
+ * Each column is represented by a Var for the corresponding base-relation
+ * column, or an expression in base-relation Vars, as appropriate.
+ *
+ * There are never any dropped columns in indexes, so unlike
+ * build_physical_tlist, we need no failure case.
+ */
+static List *
+build_index_tlist(PlannerInfo *root, IndexOptInfo *index,
+				  Relation heapRelation)
+{
+	List	   *tlist = NIL;
+	Index		varno = index->rel->relid;
+	ListCell   *indexpr_item;
+	int			i;
+
+	indexpr_item = list_head(index->indexprs);
+	for (i = 0; i < index->ncolumns; i++)
+	{
+		int			indexkey = index->indexkeys[i];
+		Expr	   *indexvar;
+
+		if (indexkey != 0)
+		{
+			/* simple column */
+			Form_pg_attribute att_tup;
+
+			if (indexkey < 0)
+				att_tup = SystemAttributeDefinition(indexkey,
+											heapRelation->rd_rel->relhasoids);
+			else
+				att_tup = heapRelation->rd_att->attrs[indexkey - 1];
+
+			indexvar = (Expr *) makeVar(varno,
+										indexkey,
+										att_tup->atttypid,
+										att_tup->atttypmod,
+										att_tup->attcollation,
+										0);
+		}
+		else
+		{
+			/* expression column */
+			if (indexpr_item == NULL)
+				elog(ERROR, "wrong number of index expressions");
+			indexvar = (Expr *) lfirst(indexpr_item);
+			indexpr_item = lnext(indexpr_item);
+		}
+
+		tlist = lappend(tlist,
+						makeTargetEntry(indexvar,
+										i + 1,
+										NULL,
+										false));
+	}
+	if (indexpr_item != NULL)
+		elog(ERROR, "wrong number of index expressions");
+
+	return tlist;
+}
+
 /*
  * restriction_selectivity
  *

src/backend/utils/adt/ruleutils.c

@@ -107,9 +107,11 @@ typedef struct
  * deparse_namespace list (since a plan tree never contains Vars with
  * varlevelsup > 0).  We store the PlanState node that is the immediate
  * parent of the expression to be deparsed, as well as a list of that
- * PlanState's ancestors.  In addition, we store the outer and inner
+ * PlanState's ancestors.  In addition, we store its outer and inner subplan
- * subplan nodes, whose targetlists are used to resolve OUTER and INNER Vars.
+ * state nodes, as well as their plan nodes' targetlists, and the indextlist
- * (Note: these could be derived on-the-fly from the planstate instead.)
+ * if the current PlanState is an IndexOnlyScanState.  (These fields could
+ * be derived on-the-fly from the current PlanState, but it seems notationally
+ * clearer to set them up as separate fields.)
  */
 typedef struct
 {
@@ -118,10 +120,11 @@ typedef struct
 	/* Remaining fields are used only when deparsing a Plan tree: */
 	PlanState  *planstate;		/* immediate parent of current expression */
 	List	   *ancestors;		/* ancestors of planstate */
-	PlanState  *outer_planstate;	/* OUTER subplan state, or NULL if none */
+	PlanState  *outer_planstate;	/* outer subplan state, or NULL if none */
-	PlanState  *inner_planstate;	/* INNER subplan state, or NULL if none */
+	PlanState  *inner_planstate;	/* inner subplan state, or NULL if none */
-	Plan	   *outer_plan;		/* OUTER subplan, or NULL if none */
+	List	   *outer_tlist;	/* referent for OUTER_VAR Vars */
-	Plan	   *inner_plan;		/* INNER subplan, or NULL if none */
+	List	   *inner_tlist;	/* referent for INNER_VAR Vars */
+	List	   *index_tlist;	/* referent for INDEX_VAR Vars */
 } deparse_namespace;
 
 
@@ -2162,9 +2165,14 @@ deparse_context_for(const char *aliasname, Oid relid)
  * deparse_context_for_planstate	- Build deparse context for a plan
  *
  * When deparsing an expression in a Plan tree, we might have to resolve
- * OUTER or INNER references.  To do this, the caller must provide the
+ * OUTER_VAR, INNER_VAR, or INDEX_VAR references.  To do this, the caller must
- * parent PlanState node.  Then OUTER and INNER references can be resolved
+ * provide the parent PlanState node.  Then OUTER_VAR and INNER_VAR references
- * by drilling down into the left and right child plans.
+ * can be resolved by drilling down into the left and right child plans.
+ * Similarly, INDEX_VAR references can be resolved by reference to the
+ * indextlist given in the parent IndexOnlyScan node.  (Note that we don't
+ * currently support deparsing of indexquals in regular IndexScan or
+ * BitmapIndexScan nodes; for those, we can only deparse the indexqualorig
+ * fields, which won't contain INDEX_VAR Vars.)
  *
  * Note: planstate really ought to be declared as "PlanState *", but we use
  * "Node *" to avoid having to include execnodes.h in builtins.h.
@@ -2175,7 +2183,7 @@ deparse_context_for(const char *aliasname, Oid relid)
  *
  * The plan's rangetable list must also be passed.  We actually prefer to use
  * the rangetable to resolve simple Vars, but the plan inputs are necessary
- * for Vars that reference expressions computed in subplan target lists.
+ * for Vars with special varnos.
  */
 List *
 deparse_context_for_planstate(Node *planstate, List *ancestors,
@@ -2201,10 +2209,11 @@ deparse_context_for_planstate(Node *planstate, List *ancestors,
  * set_deparse_planstate: set up deparse_namespace to parse subexpressions
  * of a given PlanState node
  *
- * This sets the planstate, outer_planstate, inner_planstate, outer_plan, and
+ * This sets the planstate, outer_planstate, inner_planstate, outer_tlist,
- * inner_plan fields.  Caller is responsible for adjusting the ancestors list
+ * inner_tlist, and index_tlist fields.  Caller is responsible for adjusting
- * if necessary.  Note that the rtable and ctes fields do not need to change
+ * the ancestors list if necessary.  Note that the rtable and ctes fields do
- * when shifting attention to different plan nodes in a single plan tree.
+ * not need to change when shifting attention to different plan nodes in a
+ * single plan tree.
  */
 static void
 set_deparse_planstate(deparse_namespace *dpns, PlanState *ps)
@@ -2229,9 +2238,9 @@ set_deparse_planstate(deparse_namespace *dpns, PlanState *ps)
 		dpns->outer_planstate = outerPlanState(ps);
 
 	if (dpns->outer_planstate)
-		dpns->outer_plan = dpns->outer_planstate->plan;
+		dpns->outer_tlist = dpns->outer_planstate->plan->targetlist;
 	else
-		dpns->outer_plan = NULL;
+		dpns->outer_tlist = NIL;
 
 	/*
 	 * For a SubqueryScan, pretend the subplan is INNER referent.  (We don't
@@ -2246,18 +2255,25 @@ set_deparse_planstate(deparse_namespace *dpns, PlanState *ps)
 		dpns->inner_planstate = innerPlanState(ps);
 
 	if (dpns->inner_planstate)
-		dpns->inner_plan = dpns->inner_planstate->plan;
+		dpns->inner_tlist = dpns->inner_planstate->plan->targetlist;
 	else
-		dpns->inner_plan = NULL;
+		dpns->inner_tlist = NIL;
+
+	/* index_tlist is set only if it's an IndexOnlyScan */
+	if (IsA(ps->plan, IndexOnlyScan))
+		dpns->index_tlist = ((IndexOnlyScan *) ps->plan)->indextlist;
+	else
+		dpns->index_tlist = NIL;
 }
 
 /*
  * push_child_plan: temporarily transfer deparsing attention to a child plan
  *
- * When expanding an OUTER or INNER reference, we must adjust the deparse
+ * When expanding an OUTER_VAR or INNER_VAR reference, we must adjust the
- * context in case the referenced expression itself uses OUTER/INNER.	We
+ * deparse context in case the referenced expression itself uses
- * modify the top stack entry in-place to avoid affecting levelsup issues
+ * OUTER_VAR/INNER_VAR.  We modify the top stack entry in-place to avoid
- * (although in a Plan tree there really shouldn't be any).
+ * affecting levelsup issues (although in a Plan tree there really shouldn't
+ * be any).
  *
  * Caller must provide a local deparse_namespace variable to save the
  * previous state for pop_child_plan.
@@ -2271,10 +2287,11 @@ push_child_plan(deparse_namespace *dpns, PlanState *ps,
 
 	/*
 	 * Currently we don't bother to adjust the ancestors list, because an
-	 * OUTER or INNER reference really shouldn't contain any Params that would
+	 * OUTER_VAR or INNER_VAR reference really shouldn't contain any Params
-	 * be set by the parent node itself.  If we did want to adjust it,
+	 * that would be set by the parent node itself.  If we did want to adjust
-	 * lcons'ing dpns->planstate onto dpns->ancestors would be the appropriate
+	 * the list, lcons'ing dpns->planstate onto dpns->ancestors would be the
-	 * thing --- and pop_child_plan would need to undo the change to the list.
+	 * appropriate thing --- and pop_child_plan would need to undo the change
+	 * to the list.
 	 */
 
 	/* Set attention on selected child */
@@ -2298,7 +2315,7 @@ pop_child_plan(deparse_namespace *dpns, deparse_namespace *save_dpns)
  * When expanding a Param reference, we must adjust the deparse context
  * to match the plan node that contains the expression being printed;
  * otherwise we'd fail if that expression itself contains a Param or
- * OUTER/INNER variables.
+ * OUTER_VAR/INNER_VAR/INDEX_VAR variable.
  *
  * The target ancestor is conveniently identified by the ListCell holding it
  * in dpns->ancestors.
@@ -3716,22 +3733,22 @@ get_variable(Var *var, int levelsup, bool showstar, deparse_context *context)
 
 	/*
 	 * Try to find the relevant RTE in this rtable.  In a plan tree, it's
-	 * likely that varno is OUTER or INNER, in which case we must dig down
+	 * likely that varno is OUTER_VAR or INNER_VAR, in which case we must dig
-	 * into the subplans.
+	 * down into the subplans, or INDEX_VAR, which is resolved similarly.
 	 */
 	if (var->varno >= 1 && var->varno <= list_length(dpns->rtable))
 	{
 		rte = rt_fetch(var->varno, dpns->rtable);
 		attnum = var->varattno;
 	}
-	else if (var->varno == OUTER && dpns->outer_plan)
+	else if (var->varno == OUTER_VAR && dpns->outer_tlist)
 	{
 		TargetEntry *tle;
 		deparse_namespace save_dpns;
 
-		tle = get_tle_by_resno(dpns->outer_plan->targetlist, var->varattno);
+		tle = get_tle_by_resno(dpns->outer_tlist, var->varattno);
 		if (!tle)
-			elog(ERROR, "bogus varattno for OUTER var: %d", var->varattno);
+			elog(ERROR, "bogus varattno for OUTER_VAR var: %d", var->varattno);
 
 		Assert(netlevelsup == 0);
 		push_child_plan(dpns, dpns->outer_planstate, &save_dpns);
@@ -3749,14 +3766,14 @@ get_variable(Var *var, int levelsup, bool showstar, deparse_context *context)
 		pop_child_plan(dpns, &save_dpns);
 		return NULL;
 	}
-	else if (var->varno == INNER && dpns->inner_plan)
+	else if (var->varno == INNER_VAR && dpns->inner_tlist)
 	{
 		TargetEntry *tle;
 		deparse_namespace save_dpns;
 
-		tle = get_tle_by_resno(dpns->inner_plan->targetlist, var->varattno);
+		tle = get_tle_by_resno(dpns->inner_tlist, var->varattno);
 		if (!tle)
-			elog(ERROR, "bogus varattno for INNER var: %d", var->varattno);
+			elog(ERROR, "bogus varattno for INNER_VAR var: %d", var->varattno);
 
 		Assert(netlevelsup == 0);
 		push_child_plan(dpns, dpns->inner_planstate, &save_dpns);
@@ -3774,6 +3791,28 @@ get_variable(Var *var, int levelsup, bool showstar, deparse_context *context)
 		pop_child_plan(dpns, &save_dpns);
 		return NULL;
 	}
+	else if (var->varno == INDEX_VAR && dpns->index_tlist)
+	{
+		TargetEntry *tle;
+
+		tle = get_tle_by_resno(dpns->index_tlist, var->varattno);
+		if (!tle)
+			elog(ERROR, "bogus varattno for INDEX_VAR var: %d", var->varattno);
+
+		Assert(netlevelsup == 0);
+
+		/*
+		 * Force parentheses because our caller probably assumed a Var is a
+		 * simple expression.
+		 */
+		if (!IsA(tle->expr, Var))
+			appendStringInfoChar(buf, '(');
+		get_rule_expr((Node *) tle->expr, context, true);
+		if (!IsA(tle->expr, Var))
+			appendStringInfoChar(buf, ')');
+
+		return NULL;
+	}
 	else
 	{
 		elog(ERROR, "bogus varno: %d", var->varno);
@@ -3789,16 +3828,16 @@ get_variable(Var *var, int levelsup, bool showstar, deparse_context *context)
 	 * no alias.  So in that case, drill down to the subplan and print the
 	 * contents of the referenced tlist item.  This works because in a plan
 	 * tree, such Vars can only occur in a SubqueryScan or CteScan node, and
-	 * we'll have set dpns->inner_plan to reference the child plan node.
+	 * we'll have set dpns->inner_planstate to reference the child plan node.
 	 */
 	if ((rte->rtekind == RTE_SUBQUERY || rte->rtekind == RTE_CTE) &&
 		attnum > list_length(rte->eref->colnames) &&
-		dpns->inner_plan)
+		dpns->inner_planstate)
 	{
 		TargetEntry *tle;
 		deparse_namespace save_dpns;
 
-		tle = get_tle_by_resno(dpns->inner_plan->targetlist, var->varattno);
+		tle = get_tle_by_resno(dpns->inner_tlist, var->varattno);
 		if (!tle)
 			elog(ERROR, "bogus varattno for subquery var: %d", var->varattno);
 
@@ -3984,23 +4023,23 @@ get_name_for_var_field(Var *var, int fieldno,
 
 	/*
 	 * Try to find the relevant RTE in this rtable.  In a plan tree, it's
-	 * likely that varno is OUTER or INNER, in which case we must dig down
+	 * likely that varno is OUTER_VAR or INNER_VAR, in which case we must dig
-	 * into the subplans.
+	 * down into the subplans, or INDEX_VAR, which is resolved similarly.
 	 */
 	if (var->varno >= 1 && var->varno <= list_length(dpns->rtable))
 	{
 		rte = rt_fetch(var->varno, dpns->rtable);
 		attnum = var->varattno;
 	}
-	else if (var->varno == OUTER && dpns->outer_plan)
+	else if (var->varno == OUTER_VAR && dpns->outer_tlist)
 	{
 		TargetEntry *tle;
 		deparse_namespace save_dpns;
 		const char *result;
 
-		tle = get_tle_by_resno(dpns->outer_plan->targetlist, var->varattno);
+		tle = get_tle_by_resno(dpns->outer_tlist, var->varattno);
 		if (!tle)
-			elog(ERROR, "bogus varattno for OUTER var: %d", var->varattno);
+			elog(ERROR, "bogus varattno for OUTER_VAR var: %d", var->varattno);
 
 		Assert(netlevelsup == 0);
 		push_child_plan(dpns, dpns->outer_planstate, &save_dpns);
@@ -4011,15 +4050,15 @@ get_name_for_var_field(Var *var, int fieldno,
 		pop_child_plan(dpns, &save_dpns);
 		return result;
 	}
-	else if (var->varno == INNER && dpns->inner_plan)
+	else if (var->varno == INNER_VAR && dpns->inner_tlist)
 	{
 		TargetEntry *tle;
 		deparse_namespace save_dpns;
 		const char *result;
 
-		tle = get_tle_by_resno(dpns->inner_plan->targetlist, var->varattno);
+		tle = get_tle_by_resno(dpns->inner_tlist, var->varattno);
 		if (!tle)
-			elog(ERROR, "bogus varattno for INNER var: %d", var->varattno);
+			elog(ERROR, "bogus varattno for INNER_VAR var: %d", var->varattno);
 
 		Assert(netlevelsup == 0);
 		push_child_plan(dpns, dpns->inner_planstate, &save_dpns);
@@ -4030,6 +4069,22 @@ get_name_for_var_field(Var *var, int fieldno,
 		pop_child_plan(dpns, &save_dpns);
 		return result;
 	}
+	else if (var->varno == INDEX_VAR && dpns->index_tlist)
+	{
+		TargetEntry *tle;
+		const char *result;
+
+		tle = get_tle_by_resno(dpns->index_tlist, var->varattno);
+		if (!tle)
+			elog(ERROR, "bogus varattno for INDEX_VAR var: %d", var->varattno);
+
+		Assert(netlevelsup == 0);
+
+		result = get_name_for_var_field((Var *) tle->expr, fieldno,
+										levelsup, context);
+
+		return result;
+	}
 	else
 	{
 		elog(ERROR, "bogus varno: %d", var->varno);
@@ -4115,11 +4170,10 @@ get_name_for_var_field(Var *var, int fieldno,
 					deparse_namespace save_dpns;
 					const char *result;
 
-					if (!dpns->inner_plan)
+					if (!dpns->inner_planstate)
 						elog(ERROR, "failed to find plan for subquery %s",
 							 rte->eref->aliasname);
-					tle = get_tle_by_resno(dpns->inner_plan->targetlist,
+					tle = get_tle_by_resno(dpns->inner_tlist, attnum);
-										   attnum);
 					if (!tle)
 						elog(ERROR, "bogus varattno for subquery var: %d",
 							 attnum);
@@ -4232,11 +4286,10 @@ get_name_for_var_field(Var *var, int fieldno,
 					deparse_namespace save_dpns;
 					const char *result;
 
-					if (!dpns->inner_plan)
+					if (!dpns->inner_planstate)
 						elog(ERROR, "failed to find plan for CTE %s",
 							 rte->eref->aliasname);
-					tle = get_tle_by_resno(dpns->inner_plan->targetlist,
+					tle = get_tle_by_resno(dpns->inner_tlist, attnum);
-										   attnum);
 					if (!tle)
 						elog(ERROR, "bogus varattno for subquery var: %d",
 							 attnum);

src/backend/utils/adt/tid.c

@@ -306,7 +306,7 @@ currtid_for_view(Relation viewrel, ItemPointer tid)
 				Var		   *var = (Var *) tle->expr;
 				RangeTblEntry *rte;
 
-				if (var->varno > 0 && var->varno < INNER &&
+				if (!IS_SPECIAL_VARNO(var->varno) &&
 					var->varattno == SelfItemPointerAttributeNumber)
 				{
 					rte = rt_fetch(var->varno, query->rtable);

src/include/executor/nodeIndexonlyscan.h

@@ -0,0 +1,26 @@
+/*-------------------------------------------------------------------------
+ *
+ * nodeIndexonlyscan.h
+ *
+ *
+ *
+ * Portions Copyright (c) 1996-2011, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/include/executor/nodeIndexonlyscan.h
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef NODEINDEXONLYSCAN_H
+#define NODEINDEXONLYSCAN_H
+
+#include "nodes/execnodes.h"
+
+extern IndexOnlyScanState *ExecInitIndexOnlyScan(IndexOnlyScan *node, EState *estate, int eflags);
+extern TupleTableSlot *ExecIndexOnlyScan(IndexOnlyScanState *node);
+extern void ExecEndIndexOnlyScan(IndexOnlyScanState *node);
+extern void ExecIndexOnlyMarkPos(IndexOnlyScanState *node);
+extern void ExecIndexOnlyRestrPos(IndexOnlyScanState *node);
+extern void ExecReScanIndexOnlyScan(IndexOnlyScanState *node);
+
+#endif   /* NODEINDEXONLYSCAN_H */

src/include/executor/nodeIndexscan.h

@@ -23,9 +23,12 @@ extern void ExecIndexMarkPos(IndexScanState *node);
 extern void ExecIndexRestrPos(IndexScanState *node);
 extern void ExecReScanIndexScan(IndexScanState *node);
 
-/* routines exported to share code with nodeBitmapIndexscan.c */
+/*
+ * These routines are exported to share code with nodeIndexonlyscan.c and
+ * nodeBitmapIndexscan.c
+ */
 extern void ExecIndexBuildScanKeys(PlanState *planstate, Relation index,
-					   Index scanrelid, List *quals, bool isorderby,
+					   List *quals, bool isorderby,
 					   ScanKey *scanKeys, int *numScanKeys,
 					   IndexRuntimeKeyInfo **runtimeKeys, int *numRuntimeKeys,
 					   IndexArrayKeyInfo **arrayKeys, int *numArrayKeys);

src/include/nodes/execnodes.h

@@ -1226,7 +1226,6 @@ typedef struct
  *		RuntimeContext	   expr context for evaling runtime Skeys
  *		RelationDesc	   index relation descriptor
  *		ScanDesc		   index scan descriptor
- *		VMBuffer		   buffer in use for visibility map testing, if any
  * ----------------
  */
 typedef struct IndexScanState
@@ -1243,9 +1242,42 @@ typedef struct IndexScanState
 	ExprContext *iss_RuntimeContext;
 	Relation	iss_RelationDesc;
 	IndexScanDesc iss_ScanDesc;
-	Buffer		iss_VMBuffer;
 } IndexScanState;
 
+/* ----------------
+ *	 IndexOnlyScanState information
+ *
+ *		indexqual		   execution state for indexqual expressions
+ *		ScanKeys		   Skey structures for index quals
+ *		NumScanKeys		   number of ScanKeys
+ *		OrderByKeys		   Skey structures for index ordering operators
+ *		NumOrderByKeys	   number of OrderByKeys
+ *		RuntimeKeys		   info about Skeys that must be evaluated at runtime
+ *		NumRuntimeKeys	   number of RuntimeKeys
+ *		RuntimeKeysReady   true if runtime Skeys have been computed
+ *		RuntimeContext	   expr context for evaling runtime Skeys
+ *		RelationDesc	   index relation descriptor
+ *		ScanDesc		   index scan descriptor
+ *		VMBuffer		   buffer in use for visibility map testing, if any
+ * ----------------
+ */
+typedef struct IndexOnlyScanState
+{
+	ScanState	ss;				/* its first field is NodeTag */
+	List	   *indexqual;
+	ScanKey		ioss_ScanKeys;
+	int			ioss_NumScanKeys;
+	ScanKey		ioss_OrderByKeys;
+	int			ioss_NumOrderByKeys;
+	IndexRuntimeKeyInfo *ioss_RuntimeKeys;
+	int			ioss_NumRuntimeKeys;
+	bool		ioss_RuntimeKeysReady;
+	ExprContext *ioss_RuntimeContext;
+	Relation	ioss_RelationDesc;
+	IndexScanDesc ioss_ScanDesc;
+	Buffer		ioss_VMBuffer;
+} IndexOnlyScanState;
+
 /* ----------------
  *	 BitmapIndexScanState information
  *

src/include/nodes/nodes.h

@@ -52,6 +52,7 @@ typedef enum NodeTag
 	T_Scan,
 	T_SeqScan,
 	T_IndexScan,
+	T_IndexOnlyScan,
 	T_BitmapIndexScan,
 	T_BitmapHeapScan,
 	T_TidScan,
@@ -97,6 +98,7 @@ typedef enum NodeTag
 	T_ScanState,
 	T_SeqScanState,
 	T_IndexScanState,
+	T_IndexOnlyScanState,
 	T_BitmapIndexScanState,
 	T_BitmapHeapScanState,
 	T_TidScanState,

src/include/nodes/plannodes.h

@@ -285,11 +285,8 @@ typedef Scan SeqScan;
  *
  * indexqual has the same form, but the expressions have been commuted if
  * necessary to put the indexkeys on the left, and the indexkeys are replaced
- * by Var nodes identifying the index columns (varattno is the index column
+ * by Var nodes identifying the index columns (their varno is INDEX_VAR and
- * position, not the base table's column, even though varno is for the base
+ * their varattno is the index column number).
- * table).	This is a bit hokey ... would be cleaner to use a special-purpose
- * node type that could not be mistaken for a regular Var.	But it will do
- * for now.
  *
  * indexorderbyorig is similarly the original form of any ORDER BY expressions
  * that are being implemented by the index, while indexorderby is modified to
@@ -302,8 +299,7 @@ typedef Scan SeqScan;
  * (Note these fields are used for amcanorderbyop cases, not amcanorder cases.)
  *
  * indexorderdir specifies the scan ordering, for indexscans on amcanorder
- * indexes (for other indexes it should be "don't care").  indexonly specifies
+ * indexes (for other indexes it should be "don't care").
- * an index-only scan, for indexscans on amcanreturn indexes.
  * ----------------
  */
 typedef struct IndexScan
@@ -315,9 +311,35 @@ typedef struct IndexScan
 	List	   *indexorderby;	/* list of index ORDER BY exprs */
 	List	   *indexorderbyorig;		/* the same in original form */
 	ScanDirection indexorderdir;	/* forward or backward or don't care */
-	bool		indexonly;		/* attempt to skip heap fetches? */
 } IndexScan;
 
+/* ----------------
+ *		index-only scan node
+ *
+ * IndexOnlyScan is very similar to IndexScan, but it specifies an
+ * index-only scan, in which the data comes from the index not the heap.
+ * Because of this, *all* Vars in the plan node's targetlist, qual, and
+ * index expressions reference index columns and have varno = INDEX_VAR.
+ * Hence we do not need separate indexqualorig and indexorderbyorig lists,
+ * since their contents would be equivalent to indexqual and indexorderby.
+ *
+ * To help EXPLAIN interpret the index Vars for display, we provide
+ * indextlist, which represents the contents of the index as a targetlist
+ * with one TLE per index column.  Vars appearing in this list reference
+ * the base table, and this is the only field in the plan node that may
+ * contain such Vars.
+ * ----------------
+ */
+typedef struct IndexOnlyScan
+{
+	Scan		scan;
+	Oid			indexid;		/* OID of index to scan */
+	List	   *indexqual;		/* list of index quals (usually OpExprs) */
+	List	   *indexorderby;	/* list of index ORDER BY exprs */
+	List	   *indextlist;		/* TargetEntry list describing index's cols */
+	ScanDirection indexorderdir;	/* forward or backward or don't care */
+} IndexOnlyScan;
+
 /* ----------------
  *		bitmap index scan node
  *

src/include/nodes/primnodes.h

@@ -118,15 +118,19 @@ typedef struct Expr
  * Note: during parsing/planning, varnoold/varoattno are always just copies
  * of varno/varattno.  At the tail end of planning, Var nodes appearing in
  * upper-level plan nodes are reassigned to point to the outputs of their
- * subplans; for example, in a join node varno becomes INNER or OUTER and
+ * subplans; for example, in a join node varno becomes INNER_VAR or OUTER_VAR
- * varattno becomes the index of the proper element of that subplan's target
+ * and varattno becomes the index of the proper element of that subplan's
- * list.  But varnoold/varoattno continue to hold the original values.
+ * target list.  But varnoold/varoattno continue to hold the original values.
  * The code doesn't really need varnoold/varoattno, but they are very useful
  * for debugging and interpreting completed plans, so we keep them around.
  */
-#define    INNER		65000
+#define    INNER_VAR		65000			/* reference to inner subplan */
-#define    OUTER		65001
+#define    OUTER_VAR		65001			/* reference to outer subplan */
+#define    INDEX_VAR		65002			/* reference to index column */
 
+#define IS_SPECIAL_VARNO(varno)		((varno) >= INNER_VAR)
+
+/* Symbols for the indexes of the special RTE entries in rules */
 #define    PRS2_OLD_VARNO			1
 #define    PRS2_NEW_VARNO			2
 
@@ -134,7 +138,7 @@ typedef struct Var
 {
 	Expr		xpr;
 	Index		varno;			/* index of this var's relation in the range
-								 * table (could also be INNER or OUTER) */
+								 * table, or INNER_VAR/OUTER_VAR/INDEX_VAR */
 	AttrNumber	varattno;		/* attribute number of this var, or zero for
 								 * all */
 	Oid			vartype;		/* pg_type OID for the type of this var */

src/include/nodes/relation.h

@@ -449,6 +449,10 @@ typedef struct RelOptInfo
  *		The indexprs and indpred expressions have been run through
  *		prepqual.c and eval_const_expressions() for ease of matching to
  *		WHERE clauses. indpred is in implicit-AND form.
+ *
+ *		indextlist is a TargetEntry list representing the index columns.
+ *		It provides an equivalent base-relation Var for each simple column,
+ *		and links to the matching indexprs element for each expression column.
  */
 typedef struct IndexOptInfo
 {
@@ -478,6 +482,8 @@ typedef struct IndexOptInfo
 	List	   *indexprs;		/* expressions for non-simple index columns */
 	List	   *indpred;		/* predicate if a partial index, else NIL */
 
+	List	   *indextlist;		/* targetlist representing index columns */
+
 	bool		predOK;			/* true if predicate matches query */
 	bool		unique;			/* true if a unique index */
 	bool		hypothetical;	/* true if index doesn't really exist */
@@ -640,6 +646,9 @@ typedef struct Path
 /*----------
  * IndexPath represents an index scan over a single index.
  *
+ * This struct is used for both regular indexscans and index-only scans;
+ * path.pathtype is T_IndexScan or T_IndexOnlyScan to show which is meant.
+ *
  * 'indexinfo' is the index to be scanned.
  *
  * 'indexclauses' is a list of index qualification clauses, with implicit
@@ -673,14 +682,10 @@ typedef struct Path
  * NoMovementScanDirection for an indexscan, but the planner wants to
  * distinguish ordered from unordered indexes for building pathkeys.)
  *
- * 'indexonly' is TRUE for an index-only scan, that is, the index's access
- * method has amcanreturn = TRUE and we only need columns available from the
- * index.
- *
  * 'indextotalcost' and 'indexselectivity' are saved in the IndexPath so that
  * we need not recompute them when considering using the same index in a
  * bitmap index/heap scan (see BitmapHeapPath).  The costs of the IndexPath
- * itself represent the costs of an IndexScan plan type.
+ * itself represent the costs of an IndexScan or IndexOnlyScan plan type.
  *
  * 'rows' is the estimated result tuple count for the indexscan.  This
  * is the same as path.parent->rows for a simple indexscan, but it is
@@ -698,7 +703,6 @@ typedef struct IndexPath
 	List	   *indexorderbys;
 	bool		isjoininner;
 	ScanDirection indexscandir;
-	bool		indexonly;
 	Cost		indextotalcost;
 	Selectivity indexselectivity;
 	double		rows;			/* estimated number of result tuples */
@@ -714,11 +718,12 @@ typedef struct IndexPath
  * The individual indexscans are represented by IndexPath nodes, and any
  * logic on top of them is represented by a tree of BitmapAndPath and
  * BitmapOrPath nodes.	Notice that we can use the same IndexPath node both
- * to represent a regular IndexScan plan, and as the child of a BitmapHeapPath
+ * to represent a regular (or index-only) index scan plan, and as the child
- * that represents scanning the same index using a BitmapIndexScan.  The
+ * of a BitmapHeapPath that represents scanning the same index using a
- * startup_cost and total_cost figures of an IndexPath always represent the
+ * BitmapIndexScan.  The startup_cost and total_cost figures of an IndexPath
- * costs to use it as a regular IndexScan.	The costs of a BitmapIndexScan
+ * always represent the costs to use it as a regular (or index-only)
- * can be computed using the IndexPath's indextotalcost and indexselectivity.
+ * IndexScan.  The costs of a BitmapIndexScan can be computed using the
+ * IndexPath's indextotalcost and indexselectivity.
  *
  * BitmapHeapPaths can be nestloop inner indexscans.  The isjoininner and
  * rows fields serve the same purpose as for plain IndexPaths.