Pass the array size to GPORCA when do array comparion

When the size of the array is more than `100` our translator does not expand the arrays.
This make GPORCA's cardinality estimation model think it is an unsupported predicate
which in turn makes it the cardinality wrong:

```
create table foo(a int, b int);
insert into foo select i, i from generate_series(1,100) i;
```

Next force GPORCA to not expand the array

```
vraghavan=# set optimizer_array_expansion_threshold = 1;
SET
vraghavan=# explain select * from foo where b in (1, 2, 3);                                                                                                                                                                                                                                                                                                                                           QUERY PLAN
-------------------------------------------------------------------------------
 Gather Motion 3:1  (slice1; segments: 3)  (cost=0.00..431.00 rows=40 width=8)
   ->  Table Scan on foo  (cost=0.00..431.00 rows=14 width=8)
         Filter: b = ANY ('{1,2,3}'::integer[])
 Settings:  optimizer_array_expansion_threshold=1
 Optimizer status: PQO version 2.75.0
(5 rows)
```

In the example,:

* Table has 100 rows
* Each column has unique value for b
* Array of the in clause has 3 values. So cardinality must be at most 3.
* Since the array is not expanded we get wrong cardinality estimation

In this change, we pass the size of the array constant so that GPORCA can try do a
better job estimating cardinality.

Associated GPORCA PR: https://github.com/greenplum-db/gporca/pull/405

src/backend/gpopt/gpdbwrappers.cpp

@@ -2966,12 +2966,13 @@ gpdb::DefGetString
 Expr *
 gpdb::TransformArrayConstToArrayExpr
 	(
-	Const *c
+	Const *c,
+	int *arrayLen
 	)
 {
 	GP_WRAP_START;
 	{
-		return transform_array_Const_to_ArrayExpr(c);
+		return transform_array_Const_to_ArrayExpr(c, arrayLen);
 	}
 	GP_WRAP_END;
 	return NULL;

src/backend/gpopt/translate/CTranslatorScalarToDXL.cpp

@@ -514,12 +514,13 @@ CTranslatorScalarToDXL::CreateScalarArrayCompFromExpr
 
 	Expr *right_expr = (Expr*) gpdb::ListNth(scalar_array_op_expr->args, 1);
 
+	int arrayLen = 0;
 	// If the argument array is an array Const, try to transform it to an
 	// ArrayExpr, to allow ORCA to optimize it better. (ORCA knows how to
 	// extract elements of an ArrayExpr, but doesn't currently know how
 	// to do it from an array-typed Const.)
 	if (IsA(right_expr, Const))
-		right_expr = gpdb::TransformArrayConstToArrayExpr((Const *) right_expr);
+		right_expr = gpdb::TransformArrayConstToArrayExpr((Const *) right_expr, &arrayLen);
 
 	CDXLNode *right_node = TranslateScalarToDXL(right_expr, var_colid_mapping);
 
@@ -541,7 +542,14 @@ CTranslatorScalarToDXL::CreateScalarArrayCompFromExpr
 		type = Edxlarraycomptypeall;
 	}
 
-	CDXLScalarArrayComp *dxlop = GPOS_NEW(m_mp) CDXLScalarArrayComp(m_mp, GPOS_NEW(m_mp) CMDIdGPDB(scalar_array_op_expr->opno), GPOS_NEW(m_mp) CWStringConst(op_name->GetBuffer()), type);
+	CDXLScalarArrayComp *dxlop = GPOS_NEW(m_mp) CDXLScalarArrayComp
+													(
+													m_mp,
+													GPOS_NEW(m_mp) CMDIdGPDB(scalar_array_op_expr->opno),
+													GPOS_NEW(m_mp) CWStringConst(op_name->GetBuffer()),
+													type,
+													arrayLen
+													);
 
 	// create the DXL node holding the scalar opexpr
 	CDXLNode *dxlnode = GPOS_NEW(m_mp) CDXLNode(m_mp, dxlop);

src/backend/optimizer/util/clauses.c

@@ -2370,7 +2370,7 @@ fold_constants(PlannerInfo *root, Query *q, ParamListInfo boundParams, Size max_
  * large arrays.
  */
 Expr *
-transform_array_Const_to_ArrayExpr(Const *c)
+transform_array_Const_to_ArrayExpr(Const *c, int *arrayLen)
 {
 	Oid			elemtype;
 	int16		elemlen;
@@ -2395,6 +2395,7 @@ transform_array_Const_to_ArrayExpr(Const *c)
 
 	ac = DatumGetArrayTypeP(c->constvalue);
 	nelems = ArrayGetNItems(ARR_NDIM(ac), ARR_DIMS(ac));
+	*arrayLen = nelems;
 
 	/* All set, extract the elements, and an ArrayExpr to hold them. */
 	get_typlenbyvalalign(elemtype, &elemlen, &elembyval, &elemalign);

src/include/gpopt/gpdbwrappers.h

@@ -624,7 +624,7 @@ namespace gpdb {
 	char *DefGetString(DefElem *defelem);
 
 	// transform array Const to an ArrayExpr
-	Expr *TransformArrayConstToArrayExpr(Const *constant);
+	Expr *TransformArrayConstToArrayExpr(Const *constant, int *arrayLen);
 
 	// transform array Const to an ArrayExpr
 	Node *EvalConstExpressions(Node *node);

src/include/optimizer/clauses.h

@@ -108,7 +108,7 @@ extern Node *eval_const_expressions(PlannerInfo *root, Node *node);
 
 extern Query *fold_constants(PlannerInfo *root, Query *q, ParamListInfo boundParams, Size max_size);
 
-extern Expr *transform_array_Const_to_ArrayExpr(Const *c);
+extern Expr *transform_array_Const_to_ArrayExpr(Const *c, int *);
 
 extern Node *estimate_expression_value(PlannerInfo *root, Node *node);