Fix CDatumSortedSet handling of empty arrays causing errors in ORCA

Previously, when constructing CDatumSortedSet from an array expression with all
NULL elements, the aprngdatum was becoming an empty array. This caused unexpected
errors that could lead to ORCA fallback to the planner, or even coredump.

The bug has been fixed by ensuring that no unnecessary operations are performed on
the empty aprngdatum array.

Author: wuyuhao28

src/backend/gporca/libgpopt/src/base/CDatumSortedSet.cpp

@@ -36,6 +36,12 @@ CDatumSortedSet::CDatumSortedSet(CMemoryPool *mp, CExpression *pexprArray,
 			aprngdatum->Append(datum);
 		}
 	}
+
+	// ALL NULLs, just return empty set
+	if (aprngdatum->Size() == 0)
+	{
+		return;
+	}
 	aprngdatum->Sort(&CUtils::IDatumCmp);
 
 	// de-duplicate

src/test/regress/expected/gporca.out

@@ -14328,3 +14328,16 @@ ON t1.tradingday = t2.tradingday;
 (1 row)
 
 DROP TABLE t_clientinstrumentind2, t_clientproductind2;
+---------------------------------------------------------------------------------
+-- Test ALL NULL scalar array compare 
+create table DatumSortedSet_core (a int, b character varying NOT NULL) distributed by (a);
+explain select * from DatumSortedSet_core where b in (NULL, NULL);
+                                  QUERY PLAN                                   
+-------------------------------------------------------------------------------
+ Gather Motion 3:1  (slice1; segments: 3)  (cost=0.00..240.69 rows=1 width=36)
+   ->  Seq Scan on datumsortedset_core  (cost=0.00..240.67 rows=1 width=36)
+         Filter: ((b)::text = ANY ('{NULL,NULL}'::text[]))
+ Optimizer: Postgres-based planner
+(4 rows)
+
+---------------------------------------------------------------------------------

src/test/regress/expected/gporca_optimizer.out

@@ -14671,3 +14671,15 @@ ON t1.tradingday = t2.tradingday;
 (1 row)
 
 DROP TABLE t_clientinstrumentind2, t_clientproductind2;
+---------------------------------------------------------------------------------
+-- Test ALL NULL scalar array compare 
+create table DatumSortedSet_core (a int, b character varying NOT NULL) distributed by (a);
+explain select * from DatumSortedSet_core where b in (NULL, NULL);
+                QUERY PLAN                 
+-------------------------------------------
+ Result  (cost=0.00..0.00 rows=0 width=12)
+   One-Time Filter: false
+ Optimizer: GPORCA
+(3 rows)
+
+---------------------------------------------------------------------------------

src/test/regress/sql/gporca.sql

@@ -3518,6 +3518,12 @@ ON t1.tradingday = t2.tradingday;
 DROP TABLE t_clientinstrumentind2, t_clientproductind2;
 
 
+---------------------------------------------------------------------------------
+-- Test ALL NULL scalar array compare 
+create table DatumSortedSet_core (a int, b character varying NOT NULL) distributed by (a);
+explain select * from DatumSortedSet_core where b in (NULL, NULL);
+---------------------------------------------------------------------------------
+
 -- start_ignore
 DROP SCHEMA orca CASCADE;
 -- end_ignore