More fixes for lossy-GiST-distance-functions patch.

tglsfdc · tglsfdc · commit c5dd8ead403f · 2015-05-21T19:47:48.000-04:00
Paul Ramsey reported that commit 35fcb1b induced a core dump on commuted ORDER BY expressions, because it was assuming that the indexorderby expression could be found verbatim in the relevant equivalence class, but it wasn't there. We really don't need anything that complicated anyway; for the data types likely to be used for index ORDER BY operators in the foreseeable future, the exprType() of the ORDER BY expression will serve fine. (The case where we'd have to work harder is where the ORDER BY expression's result is only binary-compatible with the declared input type of the ordering operator; long before worrying about that, one would need to get rid of GiST's hard-wired assumption that said datatype is float8.) Aside from fixing that crash and adding a regression test for the case, I did some desultory code review: nodeIndexscan.c was likewise overthinking how hard it ought to work to identify the datatype of the ORDER BY expressions. Add comments explaining how come nodeIndexscan.c can get away with simplifying assumptions about NULLS LAST ordering and no backward scan. Revert no-longer-needed changes of find_ec_member_for_tle(); while the new definition was no worse than the old, it wasn't better either, and it might cause back-patching pain. Revert entirely bogus additions to genam.h.
diff --git a/src/backend/executor/nodeIndexscan.c b/src/backend/executor/nodeIndexscan.c
@@ -30,6 +30,7 @@
 #include "executor/execdebug.h"
 #include "executor/nodeIndexscan.h"
 #include "lib/pairingheap.h"
+#include "nodes/nodeFuncs.h"
 #include "optimizer/clauses.h"
 #include "utils/array.h"
 #include "utils/datum.h"
@@ -159,9 +160,18 @@ IndexNextWithReorder(IndexScanState *node)
 	bool	   *lastfetched_nulls;
 	int			cmp;
 
-	/* only forward scan is supported with reordering. */
+	/*
+	 * Only forward scan is supported with reordering.  Note: we can get away
+	 * with just Asserting here because the system will not try to run the
+	 * plan backwards if ExecSupportsBackwardScan() says it won't work.
+	 * Currently, that is guaranteed because no index AMs support both
+	 * amcanorderbyop and amcanbackward; if any ever do,
+	 * ExecSupportsBackwardScan() will need to consider indexorderbys
+	 * explicitly.
+	 */
 	Assert(!ScanDirectionIsBackward(((IndexScan *) node->ss.ps.plan)->indexorderdir));
 	Assert(ScanDirectionIsForward(node->ss.ps.state->es_direction));
+
 	scandesc = node->iss_ScanDesc;
 	econtext = node->ss.ps.ps_ExprContext;
 	slot = node->ss.ss_ScanTupleSlot;
@@ -370,7 +380,11 @@ cmp_orderbyvals(const Datum *adist, const bool *anulls,
 	{
 		SortSupport ssup = &node->iss_SortSupport[i];
 
-		/* Handle nulls.  We only support NULLS LAST. */
+		/*
+		 * Handle nulls.  We only need to support NULLS LAST ordering, because
+		 * match_pathkeys_to_index() doesn't consider indexorderby
+		 * implementation otherwise.
+		 */
 		if (anulls[i] && !bnulls[i])
 			return 1;
 		else if (!anulls[i] && bnulls[i])
@@ -388,7 +402,7 @@ cmp_orderbyvals(const Datum *adist, const bool *anulls,
 
 /*
  * Pairing heap provides getting topmost (greatest) element while KNN provides
- * ascending sort.  That's why we inverse the sort order.
+ * ascending sort.  That's why we invert the sort order.
  */
 static int
 reorderqueue_cmp(const pairingheap_node *a, const pairingheap_node *b,
@@ -917,46 +931,41 @@ ExecInitIndexScan(IndexScan *node, EState *estate, int eflags)
 	{
 		int			numOrderByKeys = indexstate->iss_NumOrderByKeys;
 		int			i;
-		ListCell   *lc;
+		ListCell   *lco;
+		ListCell   *lcx;
 
 		/*
-		 * Prepare sort support, and look up the distance type for each ORDER
-		 * BY expression.
+		 * Prepare sort support, and look up the data type for each ORDER BY
+		 * expression.
 		 */
 		Assert(numOrderByKeys == list_length(node->indexorderbyops));
-		indexstate->iss_SortSupport =
+		Assert(numOrderByKeys == list_length(node->indexorderbyorig));
+		indexstate->iss_SortSupport = (SortSupportData *)
 			palloc0(numOrderByKeys * sizeof(SortSupportData));
-		indexstate->iss_OrderByTypByVals =
+		indexstate->iss_OrderByTypByVals = (bool *)
 			palloc(numOrderByKeys * sizeof(bool));
-		indexstate->iss_OrderByTypLens =
+		indexstate->iss_OrderByTypLens = (int16 *)
 			palloc(numOrderByKeys * sizeof(int16));
 		i = 0;
-		foreach(lc, node->indexorderbyops)
+		forboth(lco, node->indexorderbyops, lcx, node->indexorderbyorig)
 		{
-			Oid orderbyop = lfirst_oid(lc);
-			Oid			orderbyType;
-			Oid			opfamily;
-			int16		strategy;
+			Oid			orderbyop = lfirst_oid(lco);
+			Node	   *orderbyexpr = (Node *) lfirst(lcx);
+			Oid			orderbyType = exprType(orderbyexpr);
 
 			PrepareSortSupportFromOrderingOp(orderbyop,
 											 &indexstate->iss_SortSupport[i]);
-
-			if (!get_ordering_op_properties(orderbyop,
-										 &opfamily, &orderbyType, &strategy))
-				elog(ERROR, "operator %u is not a valid ordering operator",
-					 orderbyop);
-
 			get_typlenbyval(orderbyType,
 							&indexstate->iss_OrderByTypLens[i],
 							&indexstate->iss_OrderByTypByVals[i]);
 			i++;
 		}
 
 		/* allocate arrays to hold the re-calculated distances */
-		indexstate->iss_OrderByValues =
-			palloc(indexstate->iss_NumOrderByKeys * sizeof(Datum));
-		indexstate->iss_OrderByNulls =
-			palloc(indexstate->iss_NumOrderByKeys * sizeof(bool));
+		indexstate->iss_OrderByValues = (Datum *)
+			palloc(numOrderByKeys * sizeof(Datum));
+		indexstate->iss_OrderByNulls = (bool *)
+			palloc(numOrderByKeys * sizeof(bool));
 
 		/* and initialize the reorder queue */
 		indexstate->iss_ReorderQueue = pairingheap_allocate(reorderqueue_cmp,
diff --git a/src/backend/optimizer/plan/createplan.c b/src/backend/optimizer/plan/createplan.c
@@ -22,7 +22,6 @@
 #include "access/stratnum.h"
 #include "access/sysattr.h"
 #include "catalog/pg_class.h"
-#include "catalog/pg_operator.h"
 #include "foreign/fdwapi.h"
 #include "miscadmin.h"
 #include "nodes/makefuncs.h"
@@ -172,8 +171,8 @@ static Plan *prepare_sort_from_pathkeys(PlannerInfo *root,
 						   Oid **p_sortOperators,
 						   Oid **p_collations,
 						   bool **p_nullsFirst);
-static EquivalenceMember *find_ec_member_for_expr(EquivalenceClass *ec,
-					   Expr *tlexpr,
+static EquivalenceMember *find_ec_member_for_tle(EquivalenceClass *ec,
+					   TargetEntry *tle,
 					   Relids relids);
 static Material *make_material(Plan *lefttree);
 
@@ -1325,36 +1324,35 @@ create_indexscan_plan(PlannerInfo *root,
 	}
 
 	/*
-	 * If there are ORDER BY expressions, look up the sort operators for
-	 * their datatypes.
+	 * If there are ORDER BY expressions, look up the sort operators for their
+	 * result datatypes.
 	 */
-	if (best_path->path.pathkeys && indexorderbys)
+	if (indexorderbys)
 	{
 		ListCell   *pathkeyCell,
 				   *exprCell;
 
 		/*
-		 * PathKey contains pointer to the equivalence class, but that's not
-		 * enough because we need the expression's datatype to look up the
-		 * sort operator in the operator family.  We have to dig out the
-		 * equivalence member for the datatype.
+		 * PathKey contains OID of the btree opfamily we're sorting by, but
+		 * that's not quite enough because we need the expression's datatype
+		 * to look up the sort operator in the operator family.
 		 */
+		Assert(list_length(best_path->path.pathkeys) == list_length(indexorderbys));
 		forboth(pathkeyCell, best_path->path.pathkeys, exprCell, indexorderbys)
 		{
 			PathKey	   *pathkey = (PathKey *) lfirst(pathkeyCell);
-			Expr	   *expr = (Expr *) lfirst(exprCell);
-			EquivalenceMember *em;
-
-			/* Find equivalence member for the order by expression */
-			em = find_ec_member_for_expr(pathkey->pk_eclass, expr, NULL);
+			Node	   *expr = (Node *) lfirst(exprCell);
+			Oid			exprtype = exprType(expr);
+			Oid			sortop;
 
 			/* Get sort operator from opfamily */
-			indexorderbyops =
-				lappend_oid(indexorderbyops,
-							get_opfamily_member(pathkey->pk_opfamily,
-												em->em_datatype,
-												em->em_datatype,
-												pathkey->pk_strategy));
+			sortop = get_opfamily_member(pathkey->pk_opfamily,
+										 exprtype,
+										 exprtype,
+										 pathkey->pk_strategy);
+			if (!OidIsValid(sortop))
+				elog(ERROR, "failed to find sort operator for ORDER BY expression");
+			indexorderbyops = lappend_oid(indexorderbyops, sortop);
 		}
 	}
 
@@ -4100,7 +4098,7 @@ prepare_sort_from_pathkeys(PlannerInfo *root, Plan *lefttree, List *pathkeys,
 			tle = get_tle_by_resno(tlist, reqColIdx[numsortkeys]);
 			if (tle)
 			{
-				em = find_ec_member_for_expr(ec, tle->expr, relids);
+				em = find_ec_member_for_tle(ec, tle, relids);
 				if (em)
 				{
 					/* found expr at right place in tlist */
@@ -4131,7 +4129,7 @@ prepare_sort_from_pathkeys(PlannerInfo *root, Plan *lefttree, List *pathkeys,
 			foreach(j, tlist)
 			{
 				tle = (TargetEntry *) lfirst(j);
-				em = find_ec_member_for_expr(ec, tle->expr, relids);
+				em = find_ec_member_for_tle(ec, tle, relids);
 				if (em)
 				{
 					/* found expr already in tlist */
@@ -4252,21 +4250,23 @@ prepare_sort_from_pathkeys(PlannerInfo *root, Plan *lefttree, List *pathkeys,
 }
 
 /*
- * find_ec_member_for_expr
- *		Locate an EquivalenceClass member matching the given expression, if any
+ * find_ec_member_for_tle
+ *		Locate an EquivalenceClass member matching the given TLE, if any
  *
  * Child EC members are ignored unless they match 'relids'.
  */
 static EquivalenceMember *
-find_ec_member_for_expr(EquivalenceClass *ec,
-						Expr *expr,
-						Relids relids)
+find_ec_member_for_tle(EquivalenceClass *ec,
+					   TargetEntry *tle,
+					   Relids relids)
 {
+	Expr	   *tlexpr;
 	ListCell   *lc;
 
 	/* We ignore binary-compatible relabeling on both ends */
-	while (expr && IsA(expr, RelabelType))
-		expr = ((RelabelType *) expr)->arg;
+	tlexpr = tle->expr;
+	while (tlexpr && IsA(tlexpr, RelabelType))
+		tlexpr = ((RelabelType *) tlexpr)->arg;
 
 	foreach(lc, ec->ec_members)
 	{
@@ -4292,7 +4292,7 @@ find_ec_member_for_expr(EquivalenceClass *ec,
 		while (emexpr && IsA(emexpr, RelabelType))
 			emexpr = ((RelabelType *) emexpr)->arg;
 
-		if (equal(emexpr, expr))
+		if (equal(emexpr, tlexpr))
 			return em;
 	}
 
diff --git a/src/include/access/genam.h b/src/include/access/genam.h
@@ -147,10 +147,7 @@ extern void index_restrpos(IndexScanDesc scan);
 extern ItemPointer index_getnext_tid(IndexScanDesc scan,
 				  ScanDirection direction);
 extern HeapTuple index_fetch_heap(IndexScanDesc scan);
-extern bool index_get_heap_values(IndexScanDesc scan, ItemPointer heapPtr,
-					Datum values[INDEX_MAX_KEYS], bool isnull[INDEX_MAX_KEYS]);
 extern HeapTuple index_getnext(IndexScanDesc scan, ScanDirection direction);
-
 extern int64 index_getbitmap(IndexScanDesc scan, TIDBitmap *bitmap);
 
 extern IndexBulkDeleteResult *index_bulk_delete(IndexVacuumInfo *info,
diff --git a/src/test/regress/expected/gist.out b/src/test/regress/expected/gist.out
@@ -86,6 +86,34 @@ order by p <-> point(0.2, 0.2);
  (0.5,0.5)
 (11 rows)
 
+-- Check commuted case as well
+explain (costs off)
+select p from gist_tbl where p <@ box(point(0,0), point(0.5, 0.5))
+order by point(0.1, 0.1) <-> p;
+                       QUERY PLAN                       
+--------------------------------------------------------
+ Index Only Scan using gist_tbl_point_index on gist_tbl
+   Index Cond: (p <@ '(0.5,0.5),(0,0)'::box)
+   Order By: (p <-> '(0.1,0.1)'::point)
+(3 rows)
+
+select p from gist_tbl where p <@ box(point(0,0), point(0.5, 0.5))
+order by point(0.1, 0.1) <-> p;
+      p      
+-------------
+ (0.1,0.1)
+ (0.15,0.15)
+ (0.05,0.05)
+ (0,0)
+ (0.2,0.2)
+ (0.25,0.25)
+ (0.3,0.3)
+ (0.35,0.35)
+ (0.4,0.4)
+ (0.45,0.45)
+ (0.5,0.5)
+(11 rows)
+
 drop index gist_tbl_point_index;
 -- Test index-only scan with box opclass
 create index gist_tbl_box_index on gist_tbl using gist (b);
diff --git a/src/test/regress/sql/gist.sql b/src/test/regress/sql/gist.sql
@@ -61,6 +61,14 @@ order by p <-> point(0.2, 0.2);
 select p from gist_tbl where p <@ box(point(0,0), point(0.5, 0.5))
 order by p <-> point(0.2, 0.2);
 
+-- Check commuted case as well
+explain (costs off)
+select p from gist_tbl where p <@ box(point(0,0), point(0.5, 0.5))
+order by point(0.1, 0.1) <-> p;
+
+select p from gist_tbl where p <@ box(point(0,0), point(0.5, 0.5))
+order by point(0.1, 0.1) <-> p;
+
 drop index gist_tbl_point_index;
 
 -- Test index-only scan with box opclass
