Remove unused function parameter in get_qual_from_partbound

Commit 0563a3a8b changed how partition constraints were generated such
that this function no longer computes the mapping of parent attnos to
child attnos.

This is an external function that extensions could use, so this is
potentially a breaking change. No external callers are known, however,
and this will make it simpler to write such callers in the future.

Author: Hou Zhijie
Reviewed-by: David Rowley, Michael Paquier, Soumyadeep Chakraborty
Discussion: https://www.postgresql.org/message-id/flat/OS0PR01MB5716A75A45BE46101A1B489894379@OS0PR01MB5716.jpnprd01.prod.outlook.com

src/backend/commands/tablecmds.c

@@ -17350,7 +17350,7 @@ ATExecAttachPartition(List **wqueue, Relation rel, PartitionCmd *cmd,
 	 * If the parent itself is a partition, make sure to include its
 	 * constraint as well.
 	 */
-	partBoundConstraint = get_qual_from_partbound(attachrel, rel, cmd->bound);
+	partBoundConstraint = get_qual_from_partbound(rel, cmd->bound);
 	partConstraint = list_concat(partBoundConstraint,
 								 RelationGetPartitionQual(rel));
 

src/backend/partitioning/partbounds.c

@@ -246,8 +246,7 @@ static List *get_range_nulltest(PartitionKey key);
  *		expressions as partition constraint
  */
 List *
-get_qual_from_partbound(Relation rel, Relation parent,
-						PartitionBoundSpec *spec)
+get_qual_from_partbound(Relation parent, PartitionBoundSpec *spec)
 {
 	PartitionKey key = RelationGetPartitionKey(parent);
 	List	   *my_qual = NIL;

src/backend/utils/cache/partcache.c

@@ -376,7 +376,7 @@ generate_partition_qual(Relation rel)
 		bound = castNode(PartitionBoundSpec,
 						 stringToNode(TextDatumGetCString(boundDatum)));
 
-		my_qual = get_qual_from_partbound(rel, parent, bound);
+		my_qual = get_qual_from_partbound(parent, bound);
 	}
 
 	ReleaseSysCache(tuple);

src/include/partitioning/partbounds.h

@@ -85,7 +85,7 @@ extern int	get_hash_partition_greatest_modulus(PartitionBoundInfo b);
 extern uint64 compute_partition_hash_value(int partnatts, FmgrInfo *partsupfunc,
 										   Oid *partcollation,
 										   Datum *values, bool *isnull);
-extern List *get_qual_from_partbound(Relation rel, Relation parent,
+extern List *get_qual_from_partbound(Relation parent,
 									 PartitionBoundSpec *spec);
 extern PartitionBoundInfo partition_bounds_create(PartitionBoundSpec **boundspecs,
 												  int nparts, PartitionKey key, int **mapping);