Use ExecPrepareExpr in place of ExecPrepareCheck where appropriate.

Change one more place where ExecInitCheck/ExecPrepareCheck's insistence
on getting implicit-AND-format quals wasn't really helpful, because the
caller had to do make_ands_implicit() for no reason that it cared about.
Using ExecPrepareExpr directly simplifies the code and saves cycles.

The only remaining use of these functions is to process
resultRelInfo->ri_PartitionCheck quals.  However, implicit-AND format
does seem to be what we want for that, so leave it alone.

src/backend/catalog/partition.c

@@ -921,8 +921,12 @@ get_qual_from_partbound(Relation rel, Relation parent, Node *bound)
  * map_partition_varattnos - maps varattno of any Vars in expr from the
  * parent attno to partition attno.
  *
- * We must allow for a case where physical attnos of a partition can be
+ * We must allow for cases where physical attnos of a partition can be
  * different from the parent's.
+ *
+ * Note: this will work on any node tree, so really the argument and result
+ * should be declared "Node *".  But a substantial majority of the callers
+ * are working on Lists, so it's less messy to do the casts internally.
  */
 List *
 map_partition_varattnos(List *expr, int target_varno,

src/backend/commands/tablecmds.c

@@ -167,7 +167,7 @@ typedef struct AlteredTableInfo
 	Oid			newTableSpace;	/* new tablespace; 0 means no change */
 	bool		chgPersistence; /* T if SET LOGGED/UNLOGGED is used */
 	char		newrelpersistence;		/* if above is true */
-	List	   *partition_constraint;	/* for attach partition validation */
+	Expr	   *partition_constraint;	/* for attach partition validation */
 	/* Objects to rebuild after completing ALTER TYPE operations */
 	List	   *changedConstraintOids;	/* OIDs of constraints to rebuild */
 	List	   *changedConstraintDefs;	/* string definitions of same */
@@ -3740,7 +3740,7 @@ ATRewriteCatalogs(List **wqueue, LOCKMODE lockmode)
 		 */
 		if (((tab->relkind == RELKIND_RELATION ||
 			  tab->relkind == RELKIND_PARTITIONED_TABLE) &&
-			 tab->partition_constraint == NIL) ||
+			 tab->partition_constraint == NULL) ||
 			tab->relkind == RELKIND_MATVIEW)
 			AlterTableCreateToastTable(tab->relid, (Datum) 0, lockmode);
 	}
@@ -4182,7 +4182,7 @@ ATRewriteTables(AlterTableStmt *parsetree, List **wqueue, LOCKMODE lockmode)
 			 * generated by ALTER TABLE commands, but don't rebuild data.
 			 */
 			if (tab->constraints != NIL || tab->new_notnull ||
-				tab->partition_constraint != NIL)
+				tab->partition_constraint != NULL)
 				ATRewriteTable(tab, InvalidOid, lockmode);
 
 			/*
@@ -4330,7 +4330,7 @@ ATRewriteTable(AlteredTableInfo *tab, Oid OIDNewHeap, LOCKMODE lockmode)
 	if (tab->partition_constraint)
 	{
 		needscan = true;
-		partqualstate = ExecPrepareCheck(tab->partition_constraint, estate);
+		partqualstate = ExecPrepareExpr(tab->partition_constraint, estate);
 	}
 
 	foreach(l, tab->newvals)
@@ -13354,9 +13354,9 @@ ATExecAttachPartition(List **wqueue, Relation rel, PartitionCmd *cmd)
 						RelationGetRelationName(attachRel))));
 
 	/*
-	 * Set up to have the table to be scanned to validate the partition
+	 * Set up to have the table be scanned to validate the partition
 	 * constraint (see partConstraint above).  If it's a partitioned table, we
-	 * instead schdule its leaf partitions to be scanned instead.
+	 * instead schedule its leaf partitions to be scanned.
 	 */
 	if (!skip_validate)
 	{
@@ -13376,7 +13376,6 @@ ATExecAttachPartition(List **wqueue, Relation rel, PartitionCmd *cmd)
 			Oid			part_relid = lfirst_oid(lc);
 			Relation	part_rel;
 			Expr	   *constr;
-			List	   *my_constr;
 
 			/* Lock already taken */
 			if (part_relid != RelationGetRelid(attachRel))
@@ -13398,12 +13397,11 @@ ATExecAttachPartition(List **wqueue, Relation rel, PartitionCmd *cmd)
 			/* Grab a work queue entry */
 			tab = ATGetQueueEntry(wqueue, part_rel);
 
+			/* Adjust constraint to match this partition */
 			constr = linitial(partConstraint);
-			my_constr = make_ands_implicit((Expr *) constr);
-			tab->partition_constraint = map_partition_varattnos(my_constr,
-																1,
-																part_rel,
-																rel);
+			tab->partition_constraint = (Expr *)
+				map_partition_varattnos((List *) constr, 1,
+										part_rel, rel);
 			/* keep our lock until commit */
 			if (part_rel != attachRel)
 				heap_close(part_rel, NoLock);