Remove some useless code

In commit 8b08f7d482 I added member relationId to IndexStmt struct.
I'm now not sure why; DefineIndex doesn't need it, since the relation
OID is passed as a separate argument anyway.  Remove it.

Also remove a redundant assignment to the relationId argument (it wasn't
redundant when added by commit e093dcdd28, but should have been removed
in commit 5f173040e3), and use relationId instead of stmt->relation when
locking the relation in the second phase of CREATE INDEX CONCURRENTLY,
which is not only confusing but it means we resolve the name twice for
no reason.

src/backend/commands/indexcmds.c

@@ -415,7 +415,6 @@ DefineIndex(Oid relationId,
 	lockmode = stmt->concurrent ? ShareUpdateExclusiveLock : ShareLock;
 	rel = heap_open(relationId, lockmode);
 
-	relationId = RelationGetRelid(rel);
 	namespaceId = RelationGetNamespace(rel);
 
 	/* Ensure that it makes sense to index this kind of relation */
@@ -1032,7 +1031,7 @@ DefineIndex(Oid relationId,
 						elog(ERROR, "cannot convert whole-row table reference");
 
 					childStmt->idxname = NULL;
-					childStmt->relationId = childRelid;
+					childStmt->relation = NULL;
 					DefineIndex(childRelid, childStmt,
 								InvalidOid, /* no predefined OID */
 								indexRelationId,	/* this is our child */
@@ -1154,7 +1153,7 @@ DefineIndex(Oid relationId,
 	 */
 
 	/* Open and lock the parent heap relation */
-	rel = heap_openrv(stmt->relation, ShareUpdateExclusiveLock);
+	rel = heap_open(relationId, ShareUpdateExclusiveLock);
 
 	/* And the target index relation */
 	indexRelation = index_open(indexRelationId, RowExclusiveLock);

src/backend/nodes/copyfuncs.c

@@ -3442,7 +3442,6 @@ _copyIndexStmt(const IndexStmt *from)
 
 	COPY_STRING_FIELD(idxname);
 	COPY_NODE_FIELD(relation);
-	COPY_SCALAR_FIELD(relationId);
 	COPY_STRING_FIELD(accessMethod);
 	COPY_STRING_FIELD(tableSpace);
 	COPY_NODE_FIELD(indexParams);

src/backend/nodes/equalfuncs.c

@@ -1325,7 +1325,6 @@ _equalIndexStmt(const IndexStmt *a, const IndexStmt *b)
 {
 	COMPARE_STRING_FIELD(idxname);
 	COMPARE_NODE_FIELD(relation);
-	COMPARE_SCALAR_FIELD(relationId);
 	COMPARE_STRING_FIELD(accessMethod);
 	COMPARE_STRING_FIELD(tableSpace);
 	COMPARE_NODE_FIELD(indexParams);

src/backend/nodes/outfuncs.c

@@ -2611,7 +2611,6 @@ _outIndexStmt(StringInfo str, const IndexStmt *node)
 
 	WRITE_STRING_FIELD(idxname);
 	WRITE_NODE_FIELD(relation);
-	WRITE_OID_FIELD(relationId);
 	WRITE_STRING_FIELD(accessMethod);
 	WRITE_STRING_FIELD(tableSpace);
 	WRITE_NODE_FIELD(indexParams);

src/backend/parser/gram.y

@@ -7338,7 +7338,6 @@ IndexStmt:	CREATE opt_unique INDEX opt_concurrently opt_index_name
 					n->concurrent = $4;
 					n->idxname = $5;
 					n->relation = $7;
-					n->relationId = InvalidOid;
 					n->accessMethod = $8;
 					n->indexParams = $10;
 					n->indexIncludingParams = $12;
@@ -7366,7 +7365,6 @@ IndexStmt:	CREATE opt_unique INDEX opt_concurrently opt_index_name
 					n->concurrent = $4;
 					n->idxname = $8;
 					n->relation = $10;
-					n->relationId = InvalidOid;
 					n->accessMethod = $11;
 					n->indexParams = $13;
 					n->indexIncludingParams = $15;

src/backend/parser/parse_utilcmd.c

@@ -1313,7 +1313,6 @@ generateClonedIndexStmt(RangeVar *heapRel, Oid heapRelid, Relation source_idx,
 	/* Begin building the IndexStmt */
 	index = makeNode(IndexStmt);
 	index->relation = heapRel;
-	index->relationId = heapRelid;
 	index->accessMethod = pstrdup(NameStr(amrec->amname));
 	if (OidIsValid(idxrelrec->reltablespace))
 		index->tableSpace = get_tablespace_name(idxrelrec->reltablespace);

src/include/nodes/parsenodes.h

@@ -2726,7 +2726,6 @@ typedef struct IndexStmt
 	NodeTag		type;
 	char	   *idxname;		/* name of new index, or NULL for default */
 	RangeVar   *relation;		/* relation to build index on */
-	Oid			relationId;		/* OID of relation to build index on */
 	char	   *accessMethod;	/* name of access method (eg. btree) */
 	char	   *tableSpace;		/* tablespace, or NULL for default */
 	List	   *indexParams;	/* columns to index: a list of IndexElem */