Allow usage of match_orclause_to_indexcol() for joins

This commit allows transformation of OR-clauses into SAOP's for index scans
within nested loop joins.  That required the following changes.

 1. Make match_orclause_to_indexcol() and group_similar_or_args() understand
    const-ness in the same way as match_opclause_to_indexcol().  This
    generally makes our approach more uniform.
 2. Make match_join_clauses_to_index() pass OR-clauses to
    match_clause_to_index().
 3. Also switch match_join_clauses_to_index() to use list_append_unique_ptr()
    for adding clauses to *joinorclauses.  That avoids possible duplicates
    when processing the same clauses with different indexes.  Previously such
    duplicates were elimited in match_clause_to_index(), but now
    group_similar_or_args() each time generates distinct copies of grouped
    OR clauses.

Discussion: https://postgr.es/m/CAPpHfdv%2BjtNwofg-p5z86jLYZUTt6tR17Wy00ta0dL%3DwHQN3ZA%40mail.gmail.com
Reviewed-by: Andrei Lepikhov <lepihov@gmail.com>
Reviewed-by: Alena Rybakina <a.rybakina@postgrespro.ru>
Reviewed-by: Pavel Borisov <pashkin.elfe@gmail.com>

Author: akorotkov

src/backend/optimizer/path/indxpath.c

@@ -1255,6 +1255,7 @@ group_similar_or_args(PlannerInfo *root, RelOptInfo *rel, RestrictInfo *rinfo)
 	ListCell   *lc2;
 	List	   *orargs;
 	List	   *result = NIL;
+	Index		relid = rel->relid;
 
 	Assert(IsA(rinfo->orclause, BoolExpr));
 	orargs = ((BoolExpr *) rinfo->orclause)->args;
@@ -1319,10 +1320,13 @@ group_similar_or_args(PlannerInfo *root, RelOptInfo *rel, RestrictInfo *rinfo)
 		/*
 		 * Check for clauses of the form: (indexkey operator constant) or
 		 * (constant operator indexkey).  But we don't know a particular index
-		 * yet.  First check for a constant, which must be Const or Param.
-		 * That's cheaper than search for an index key among all indexes.
+		 * yet.  Therefore, we try to distinguish the potential index key and
+		 * constant first, then search for a matching index key among all
+		 * indexes.
 		 */
-		if (IsA(leftop, Const) || IsA(leftop, Param))
+		if (bms_is_member(relid, argrinfo->right_relids) &&
+			!bms_is_member(relid, argrinfo->left_relids) &&
+			!contain_volatile_functions(leftop))
 		{
 			opno = get_commutator(opno);
 
@@ -1333,7 +1337,9 @@ group_similar_or_args(PlannerInfo *root, RelOptInfo *rel, RestrictInfo *rinfo)
 			}
 			nonConstExpr = rightop;
 		}
-		else if (IsA(rightop, Const) || IsA(rightop, Param))
+		else if (bms_is_member(relid, argrinfo->left_relids) &&
+				 !bms_is_member(relid, argrinfo->right_relids) &&
+				 !contain_volatile_functions(rightop))
 		{
 			nonConstExpr = leftop;
 		}
@@ -2414,6 +2420,7 @@ match_restriction_clauses_to_index(PlannerInfo *root,
  *	  Identify join clauses for the rel that match the index.
  *	  Matching clauses are added to *clauseset.
  *	  Also, add any potentially usable join OR clauses to *joinorclauses.
+ *	  They also might be processed by match_clause_to_index() as a whole.
  */
 static void
 match_join_clauses_to_index(PlannerInfo *root,
@@ -2432,11 +2439,15 @@ match_join_clauses_to_index(PlannerInfo *root,
 		if (!join_clause_is_movable_to(rinfo, rel))
 			continue;
 
-		/* Potentially usable, so see if it matches the index or is an OR */
+		/*
+		 * Potentially usable, so see if it matches the index or is an OR. Use
+		 * list_append_unique_ptr() here to avoid possible duplicates when
+		 * processing the same clauses with different indexes.
+		 */
 		if (restriction_is_or_clause(rinfo))
-			*joinorclauses = lappend(*joinorclauses, rinfo);
-		else
-			match_clause_to_index(root, rinfo, index, clauseset);
+			*joinorclauses = list_append_unique_ptr(*joinorclauses, rinfo);
+
+		match_clause_to_index(root, rinfo, index, clauseset);
 	}
 }
 
@@ -2585,10 +2596,7 @@ match_clause_to_index(PlannerInfo *root,
  *	  (3)  must match the collation of the index, if collation is relevant.
  *
  *	  Our definition of "const" is exceedingly liberal: we allow anything that
- *	  doesn't involve a volatile function or a Var of the index's relation
- *	  except for a boolean OR expression input: due to a trade-off between the
- *	  expected execution speedup and planning complexity, we limit or->saop
- *	  transformation by obvious cases when an index scan can get a profit.
+ *	  doesn't involve a volatile function or a Var of the index's relation.
  *	  In particular, Vars belonging to other relations of the query are
  *	  accepted here, since a clause of that form can be used in a
  *	  parameterized indexscan.  It's the responsibility of higher code levels
@@ -3247,7 +3255,8 @@ match_orclause_to_indexcol(PlannerInfo *root,
 	Oid			arraytype = InvalidOid;
 	Oid			inputcollid = InvalidOid;
 	bool		firstTime = true;
-	bool		haveParam = false;
+	bool		haveNonConst = false;
+	Index		indexRelid = index->rel->relid;
 
 	Assert(IsA(orclause, BoolExpr));
 	Assert(orclause->boolop == OR_EXPR);
@@ -3259,10 +3268,9 @@ match_orclause_to_indexcol(PlannerInfo *root,
 	/*
 	 * Try to convert a list of OR-clauses to a single SAOP expression. Each
 	 * OR entry must be in the form: (indexkey operator constant) or (constant
-	 * operator indexkey).  Operators of all the entries must match.  Constant
-	 * might be either Const or Param.  To be effective, give up on the first
-	 * non-matching entry.  Exit is implemented as a break from the loop,
-	 * which is catched afterwards.
+	 * operator indexkey).  Operators of all the entries must match.  To be
+	 * effective, give up on the first non-matching entry.  Exit is
+	 * implemented as a break from the loop, which is catched afterwards.
 	 */
 	foreach(lc, orclause->args)
 	{
@@ -3313,17 +3321,21 @@ match_orclause_to_indexcol(PlannerInfo *root,
 
 		/*
 		 * Check for clauses of the form: (indexkey operator constant) or
-		 * (constant operator indexkey).  Determine indexkey side first, check
-		 * the constant later.
+		 * (constant operator indexkey).  See match_clause_to_indexcol's notes
+		 * about const-ness.
 		 */
 		leftop = (Node *) linitial(subClause->args);
 		rightop = (Node *) lsecond(subClause->args);
-		if (match_index_to_operand(leftop, indexcol, index))
+		if (match_index_to_operand(leftop, indexcol, index) &&
+			!bms_is_member(indexRelid, subRinfo->right_relids) &&
+			!contain_volatile_functions(rightop))
 		{
 			indexExpr = leftop;
 			constExpr = rightop;
 		}
-		else if (match_index_to_operand(rightop, indexcol, index))
+		else if (match_index_to_operand(rightop, indexcol, index) &&
+				 !bms_is_member(indexRelid, subRinfo->left_relids) &&
+				 !contain_volatile_functions(leftop))
 		{
 			opno = get_commutator(opno);
 			if (!OidIsValid(opno))
@@ -3350,10 +3362,6 @@ match_orclause_to_indexcol(PlannerInfo *root,
 		if (IsA(indexExpr, RelabelType))
 			indexExpr = (Node *) ((RelabelType *) indexExpr)->arg;
 
-		/* We allow constant to be Const or Param */
-		if (!IsA(constExpr, Const) && !IsA(constExpr, Param))
-			break;
-
 		/* Forbid transformation for composite types, records. */
 		if (type_is_rowtype(exprType(constExpr)) ||
 			type_is_rowtype(exprType(indexExpr)))
@@ -3390,8 +3398,12 @@ match_orclause_to_indexcol(PlannerInfo *root,
 				break;
 		}
 
-		if (IsA(constExpr, Param))
-			haveParam = true;
+		/*
+		 * Check if our list of constants in match_clause_to_indexcol's
+		 * understanding of const-ness have something other than Const.
+		 */
+		if (!IsA(constExpr, Const))
+			haveNonConst = true;
 		consts = lappend(consts, constExpr);
 	}
 
@@ -3408,10 +3420,10 @@ match_orclause_to_indexcol(PlannerInfo *root,
 
 	/*
 	 * Assemble an array from the list of constants.  It seems more profitable
-	 * to build a const array.  But in the presence of parameters, we don't
+	 * to build a const array.  But in the presence of other nodes, we don't
 	 * have a specific value here and must employ an ArrayExpr instead.
 	 */
-	if (haveParam)
+	if (haveNonConst)
 	{
 		ArrayExpr  *arrayExpr = makeNode(ArrayExpr);
 

src/test/regress/expected/create_index.out

@@ -2006,6 +2006,27 @@ SELECT * FROM tenk1
    Filter: (((tenthous)::numeric = '1'::numeric) OR (tenthous = 3) OR ((tenthous)::numeric = '42'::numeric))
 (2 rows)
 
+EXPLAIN (COSTS OFF)
+SELECT count(*) FROM tenk1 t1
+  WHERE t1.thousand = 42 OR t1.thousand = (SELECT t2.tenthous FROM tenk1 t2 WHERE t2.thousand = t1.tenthous + 1 LIMIT 1);
+                                 QUERY PLAN                                 
+----------------------------------------------------------------------------
+ Aggregate
+   ->  Index Only Scan using tenk1_thous_tenthous on tenk1 t1
+         Filter: ((thousand = 42) OR (thousand = (SubPlan 1)))
+         SubPlan 1
+           ->  Limit
+                 ->  Index Only Scan using tenk1_thous_tenthous on tenk1 t2
+                       Index Cond: (thousand = (t1.tenthous + 1))
+(7 rows)
+
+SELECT count(*) FROM tenk1 t1
+  WHERE t1.thousand = 42 OR t1.thousand = (SELECT t2.tenthous FROM tenk1 t2 WHERE t2.thousand = t1.tenthous + 1 LIMIT 1);
+ count 
+-------
+    10
+(1 row)
+
 EXPLAIN (COSTS OFF)
 SELECT count(*) FROM tenk1
   WHERE hundred = 42 AND (thousand = 42 OR thousand = 99);
@@ -3255,6 +3276,17 @@ CREATE INDEX t_b_c_idx ON bitmap_split_or (b, c);
 CREATE STATISTICS t_a_b_stat (mcv) ON a, b FROM bitmap_split_or;
 CREATE STATISTICS t_b_c_stat (mcv) ON b, c FROM bitmap_split_or;
 ANALYZE bitmap_split_or;
+EXPLAIN (COSTS OFF)
+SELECT * FROM bitmap_split_or t1, bitmap_split_or t2
+WHERE t1.a = t2.b OR t1.a = 2;
+                       QUERY PLAN                       
+--------------------------------------------------------
+ Nested Loop
+   ->  Seq Scan on bitmap_split_or t2
+   ->  Index Scan using t_a_b_idx on bitmap_split_or t1
+         Index Cond: (a = ANY (ARRAY[t2.b, 2]))
+(4 rows)
+
 EXPLAIN (COSTS OFF)
 SELECT * FROM bitmap_split_or WHERE a = 1 AND (b = 1 OR b = 2) AND c = 2;
                             QUERY PLAN                            

src/test/regress/expected/join.out

@@ -3849,14 +3849,11 @@ where q1 = thousand or q2 = thousand;
                ->  Seq Scan on q2
          ->  Bitmap Heap Scan on tenk1
                Recheck Cond: ((q1.q1 = thousand) OR (q2.q2 = thousand))
-               ->  BitmapOr
-                     ->  Bitmap Index Scan on tenk1_thous_tenthous
-                           Index Cond: (thousand = q1.q1)
-                     ->  Bitmap Index Scan on tenk1_thous_tenthous
-                           Index Cond: (thousand = q2.q2)
+               ->  Bitmap Index Scan on tenk1_thous_tenthous
+                     Index Cond: (thousand = ANY (ARRAY[q1.q1, q2.q2]))
    ->  Hash
          ->  Seq Scan on int4_tbl
-(15 rows)
+(12 rows)
 
 explain (costs off)
 select * from
@@ -8239,3 +8236,45 @@ GROUP BY s.c1, s.c2;
 (7 rows)
 
 DROP TABLE group_tbl;
+--
+-- Test for a nested loop join involving index scan, transforming OR-clauses
+-- to SAOP.
+--
+EXPLAIN (COSTS OFF)
+SELECT COUNT(*) FROM tenk1 t1, tenk1 t2
+WHERE t2.thousand = t1.tenthous OR t2.thousand = t1.unique1 OR t2.thousand = t1.unique2;
+                                       QUERY PLAN                                        
+-----------------------------------------------------------------------------------------
+ Aggregate
+   ->  Nested Loop
+         ->  Seq Scan on tenk1 t1
+         ->  Index Only Scan using tenk1_thous_tenthous on tenk1 t2
+               Index Cond: (thousand = ANY (ARRAY[t1.tenthous, t1.unique1, t1.unique2]))
+(5 rows)
+
+SELECT COUNT(*) FROM tenk1 t1, tenk1 t2
+WHERE t2.thousand = t1.tenthous OR t2.thousand = t1.unique1 OR t2.thousand = t1.unique2;
+ count 
+-------
+ 20000
+(1 row)
+
+EXPLAIN (COSTS OFF)
+SELECT COUNT(*) FROM onek t1 LEFT JOIN tenk1 t2
+    ON (t2.thousand = t1.tenthous OR t2.thousand = t1.thousand);
+                                  QUERY PLAN                                  
+------------------------------------------------------------------------------
+ Aggregate
+   ->  Nested Loop Left Join
+         ->  Seq Scan on onek t1
+         ->  Index Only Scan using tenk1_thous_tenthous on tenk1 t2
+               Index Cond: (thousand = ANY (ARRAY[t1.tenthous, t1.thousand]))
+(5 rows)
+
+SELECT COUNT(*) FROM onek t1 LEFT JOIN tenk1 t2
+    ON (t2.thousand = t1.tenthous OR t2.thousand = t1.thousand);
+ count 
+-------
+ 19000
+(1 row)
+

src/test/regress/expected/partition_join.out

@@ -2533,24 +2533,24 @@ where not exists (select 1 from prtx2
          ->  Seq Scan on prtx1_1
                Filter: ((a < 20) AND (c = 91))
          ->  Bitmap Heap Scan on prtx2_1
-               Recheck Cond: ((b = (prtx1_1.b + 1)) OR (c = 99))
+               Recheck Cond: ((c = 99) OR (b = (prtx1_1.b + 1)))
                Filter: (a = prtx1_1.a)
                ->  BitmapOr
-                     ->  Bitmap Index Scan on prtx2_1_b_idx
-                           Index Cond: (b = (prtx1_1.b + 1))
                      ->  Bitmap Index Scan on prtx2_1_c_idx
                            Index Cond: (c = 99)
+                     ->  Bitmap Index Scan on prtx2_1_b_idx
+                           Index Cond: (b = (prtx1_1.b + 1))
    ->  Nested Loop Anti Join
          ->  Seq Scan on prtx1_2
                Filter: ((a < 20) AND (c = 91))
          ->  Bitmap Heap Scan on prtx2_2
-               Recheck Cond: ((b = (prtx1_2.b + 1)) OR (c = 99))
+               Recheck Cond: ((c = 99) OR (b = (prtx1_2.b + 1)))
                Filter: (a = prtx1_2.a)
                ->  BitmapOr
-                     ->  Bitmap Index Scan on prtx2_2_b_idx
-                           Index Cond: (b = (prtx1_2.b + 1))
                      ->  Bitmap Index Scan on prtx2_2_c_idx
                            Index Cond: (c = 99)
+                     ->  Bitmap Index Scan on prtx2_2_b_idx
+                           Index Cond: (b = (prtx1_2.b + 1))
 (23 rows)
 
 select * from prtx1

src/test/regress/sql/create_index.sql

@@ -781,6 +781,12 @@ EXPLAIN (COSTS OFF)
 SELECT * FROM tenk1
   WHERE tenthous = 1::numeric OR tenthous = 3::int4 OR tenthous = 42::numeric;
 
+EXPLAIN (COSTS OFF)
+SELECT count(*) FROM tenk1 t1
+  WHERE t1.thousand = 42 OR t1.thousand = (SELECT t2.tenthous FROM tenk1 t2 WHERE t2.thousand = t1.tenthous + 1 LIMIT 1);
+SELECT count(*) FROM tenk1 t1
+  WHERE t1.thousand = 42 OR t1.thousand = (SELECT t2.tenthous FROM tenk1 t2 WHERE t2.thousand = t1.tenthous + 1 LIMIT 1);
+
 EXPLAIN (COSTS OFF)
 SELECT count(*) FROM tenk1
   WHERE hundred = 42 AND (thousand = 42 OR thousand = 99);
@@ -1367,6 +1373,9 @@ CREATE STATISTICS t_a_b_stat (mcv) ON a, b FROM bitmap_split_or;
 CREATE STATISTICS t_b_c_stat (mcv) ON b, c FROM bitmap_split_or;
 ANALYZE bitmap_split_or;
 EXPLAIN (COSTS OFF)
+SELECT * FROM bitmap_split_or t1, bitmap_split_or t2
+WHERE t1.a = t2.b OR t1.a = 2;
+EXPLAIN (COSTS OFF)
 SELECT * FROM bitmap_split_or WHERE a = 1 AND (b = 1 OR b = 2) AND c = 2;
 DROP TABLE bitmap_split_or;
 

src/test/regress/sql/join.sql

@@ -3016,7 +3016,6 @@ SELECT t1.a FROM skip_fetch t1 LEFT JOIN skip_fetch t2 ON t2.a = 1 WHERE t2.a IS
 
 RESET enable_indexonlyscan;
 RESET enable_seqscan;
-
 -- Test BitmapHeapScan with a rescan releases resources correctly
 SET enable_seqscan = off;
 SET enable_indexscan = off;
@@ -3046,3 +3045,20 @@ SELECT 1 FROM group_tbl t1
 GROUP BY s.c1, s.c2;
 
 DROP TABLE group_tbl;
+
+--
+-- Test for a nested loop join involving index scan, transforming OR-clauses
+-- to SAOP.
+--
+
+EXPLAIN (COSTS OFF)
+SELECT COUNT(*) FROM tenk1 t1, tenk1 t2
+WHERE t2.thousand = t1.tenthous OR t2.thousand = t1.unique1 OR t2.thousand = t1.unique2;
+SELECT COUNT(*) FROM tenk1 t1, tenk1 t2
+WHERE t2.thousand = t1.tenthous OR t2.thousand = t1.unique1 OR t2.thousand = t1.unique2;
+
+EXPLAIN (COSTS OFF)
+SELECT COUNT(*) FROM onek t1 LEFT JOIN tenk1 t2
+    ON (t2.thousand = t1.tenthous OR t2.thousand = t1.thousand);
+SELECT COUNT(*) FROM onek t1 LEFT JOIN tenk1 t2
+    ON (t2.thousand = t1.tenthous OR t2.thousand = t1.thousand);