Fix SIGSEGV in pruning for ScalarArrayOp with constant-null array.

Not much to be said here: commit 9fdb675f should have checked
constisnull, didn't.

Per report from Piotr Włodarczyk.  Back-patch to v11 where
bug was introduced.

Discussion: https://postgr.es/m/CAP-dhMr+vRpwizEYjUjsiZ1vwqpohTm+3Pbdt6Pr7FEgPq9R0Q@mail.gmail.com

src/backend/partitioning/partprune.c

@@ -2059,7 +2059,7 @@ match_clause_to_partition_key(GeneratePruningStepsContext *context,
 			 * nodes, one for each array element (excepting nulls).
 			 */
 			Const	   *arr = (Const *) rightop;
-			ArrayType  *arrval = DatumGetArrayTypeP(arr->constvalue);
+			ArrayType  *arrval;
 			int16		elemlen;
 			bool		elembyval;
 			char		elemalign;
@@ -2068,6 +2068,11 @@ match_clause_to_partition_key(GeneratePruningStepsContext *context,
 			int			num_elems,
 						i;
 
+			/* If the array itself is null, the saop returns null */
+			if (arr->constisnull)
+				return PARTCLAUSE_MATCH_CONTRADICT;
+
+			arrval = DatumGetArrayTypeP(arr->constvalue);
 			get_typlenbyvalalign(ARR_ELEMTYPE(arrval),
 								 &elemlen, &elembyval, &elemalign);
 			deconstruct_array(arrval,

src/test/regress/expected/partition_prune.out

@@ -1186,6 +1186,58 @@ explain (costs off) select * from coercepart where a !~ all ('{ab,bc}');
          Filter: ((a)::text !~ ALL ('{ab,bc}'::text[]))
 (7 rows)
 
+explain (costs off) select * from coercepart where a = any ('{ab,bc}');
+                      QUERY PLAN                       
+-------------------------------------------------------
+ Append
+   ->  Seq Scan on coercepart_ab
+         Filter: ((a)::text = ANY ('{ab,bc}'::text[]))
+   ->  Seq Scan on coercepart_bc
+         Filter: ((a)::text = ANY ('{ab,bc}'::text[]))
+(5 rows)
+
+explain (costs off) select * from coercepart where a = any ('{ab,null}');
+                    QUERY PLAN                     
+---------------------------------------------------
+ Seq Scan on coercepart_ab
+   Filter: ((a)::text = ANY ('{ab,NULL}'::text[]))
+(2 rows)
+
+explain (costs off) select * from coercepart where a = any (null::text[]);
+        QUERY PLAN        
+--------------------------
+ Result
+   One-Time Filter: false
+(2 rows)
+
+explain (costs off) select * from coercepart where a = all ('{ab}');
+                  QUERY PLAN                  
+----------------------------------------------
+ Seq Scan on coercepart_ab
+   Filter: ((a)::text = ALL ('{ab}'::text[]))
+(2 rows)
+
+explain (costs off) select * from coercepart where a = all ('{ab,bc}');
+        QUERY PLAN        
+--------------------------
+ Result
+   One-Time Filter: false
+(2 rows)
+
+explain (costs off) select * from coercepart where a = all ('{ab,null}');
+        QUERY PLAN        
+--------------------------
+ Result
+   One-Time Filter: false
+(2 rows)
+
+explain (costs off) select * from coercepart where a = all (null::text[]);
+        QUERY PLAN        
+--------------------------
+ Result
+   One-Time Filter: false
+(2 rows)
+
 drop table coercepart;
 CREATE TABLE part (a INT, b INT) PARTITION BY LIST (a);
 CREATE TABLE part_p1 PARTITION OF part FOR VALUES IN (-2,-1,0,1,2);
@@ -3157,6 +3209,20 @@ select * from stable_qual_pruning
          Filter: (a = ANY ('{"Tue Feb 01 00:00:00 2000 PST","Fri Jan 01 00:00:00 2010 PST"}'::timestamp with time zone[]))
 (4 rows)
 
+explain (analyze, costs off, summary off, timing off)
+select * from stable_qual_pruning
+  where a = any(null::timestamptz[]);
+                           QUERY PLAN                           
+----------------------------------------------------------------
+ Append (actual rows=0 loops=1)
+   ->  Seq Scan on stable_qual_pruning1 (actual rows=0 loops=1)
+         Filter: (a = ANY (NULL::timestamp with time zone[]))
+   ->  Seq Scan on stable_qual_pruning2 (actual rows=0 loops=1)
+         Filter: (a = ANY (NULL::timestamp with time zone[]))
+   ->  Seq Scan on stable_qual_pruning3 (actual rows=0 loops=1)
+         Filter: (a = ANY (NULL::timestamp with time zone[]))
+(7 rows)
+
 drop table stable_qual_pruning;
 --
 -- Check that pruning with composite range partitioning works correctly when

src/test/regress/sql/partition_prune.sql

@@ -184,6 +184,13 @@ explain (costs off) select * from coercepart where a ~ any ('{ab}');
 explain (costs off) select * from coercepart where a !~ all ('{ab}');
 explain (costs off) select * from coercepart where a ~ any ('{ab,bc}');
 explain (costs off) select * from coercepart where a !~ all ('{ab,bc}');
+explain (costs off) select * from coercepart where a = any ('{ab,bc}');
+explain (costs off) select * from coercepart where a = any ('{ab,null}');
+explain (costs off) select * from coercepart where a = any (null::text[]);
+explain (costs off) select * from coercepart where a = all ('{ab}');
+explain (costs off) select * from coercepart where a = all ('{ab,bc}');
+explain (costs off) select * from coercepart where a = all ('{ab,null}');
+explain (costs off) select * from coercepart where a = all (null::text[]);
 
 drop table coercepart;
 
@@ -803,6 +810,9 @@ select * from stable_qual_pruning
 explain (analyze, costs off, summary off, timing off)
 select * from stable_qual_pruning
   where a = any(array['2000-02-01', '2010-01-01']::timestamptz[]);
+explain (analyze, costs off, summary off, timing off)
+select * from stable_qual_pruning
+  where a = any(null::timestamptz[]);
 
 drop table stable_qual_pruning;