Remove unnecessary smgropen() calls

Now that RelationCreateStorage() returns the SmgrRelation (since
commit 5c1560606d), use that.

Author: Japin Li
Discussion: https://www.postgresql.org/message-id/ME3P282MB316600FA62F6605477F26F6AB6742@ME3P282MB3166.AUSP282.PROD.OUTLOOK.COM

src/backend/access/heap/heapam_handler.c

@@ -633,8 +633,6 @@ heapam_relation_copy_data(Relation rel, const RelFileLocator *newrlocator)
 {
 	SMgrRelation dstrel;
 
-	dstrel = smgropen(*newrlocator, rel->rd_backend);
-
 	/*
 	 * Since we copy the file directly without looking at the shared buffers,
 	 * we'd better first flush out any pages of the source relation that are
@@ -650,7 +648,7 @@ heapam_relation_copy_data(Relation rel, const RelFileLocator *newrlocator)
 	 * NOTE: any conflict in relfilenumber value will be caught in
 	 * RelationCreateStorage().
 	 */
-	RelationCreateStorage(*newrlocator, rel->rd_rel->relpersistence, true);
+	dstrel = RelationCreateStorage(*newrlocator, rel->rd_rel->relpersistence, true);
 
 	/* copy main fork */
 	RelationCopyStorage(RelationGetSmgr(rel), dstrel, MAIN_FORKNUM,

src/backend/commands/tablecmds.c

@@ -15747,8 +15747,6 @@ index_copy_data(Relation rel, RelFileLocator newrlocator)
 {
 	SMgrRelation dstrel;
 
-	dstrel = smgropen(newrlocator, rel->rd_backend);
-
 	/*
 	 * Since we copy the file directly without looking at the shared buffers,
 	 * we'd better first flush out any pages of the source relation that are
@@ -15764,7 +15762,7 @@ index_copy_data(Relation rel, RelFileLocator newrlocator)
 	 * NOTE: any conflict in relfilenumber value will be caught in
 	 * RelationCreateStorage().
 	 */
-	RelationCreateStorage(newrlocator, rel->rd_rel->relpersistence, true);
+	dstrel = RelationCreateStorage(newrlocator, rel->rd_rel->relpersistence, true);
 
 	/* copy main fork */
 	RelationCopyStorage(RelationGetSmgr(rel), dstrel, MAIN_FORKNUM,