Fix warnings flagged by gcc.

src/backend/access/external/url_file.c

@@ -109,7 +109,7 @@ url_file_fread(void *ptr, size_t size, URL_FILE *file, CopyState pstate)
 
 		if (pstate->cdbsreh)
 			snprintf(pstate->cdbsreh->filename,
-					 sizeof pstate->cdbsreh->filename,
+					 sizeof(pstate->cdbsreh->filename),
 					 "%s [%s]", ffile->common.url, fo.fname);
 	}
 	return want;

src/backend/commands/schemacmds.c

@@ -70,7 +70,7 @@ CreateSchemaCommand(CreateSchemaStmt *stmt, const char *queryString)
 	{
 		Assert(Gp_role == GP_ROLE_EXECUTE);
 
-		Assert(stmt->schemaname == InvalidOid);
+		Assert(stmt->schemaname == NULL);
 		Assert(stmt->authid == NULL);
 		Assert(stmt->schemaElts == NIL);
 

src/backend/utils/adt/dbsize.c

@@ -687,7 +687,7 @@ pg_total_relation_size(PG_FUNCTION_ARGS)
 	 * someone else might drop the table. It's better to return NULL for
 	 * already-dropped tables than throw an error and abort the whole query.
 	 */
-	if (!OidIsValid(get_rel_name(relOid)))
+	if (get_rel_name(relOid) == NULL)
 		PG_RETURN_NULL();
 
 	size = calculate_total_relation_size(relOid);

src/include/cdb/cdbsreh.h

@@ -76,7 +76,7 @@ typedef struct CdbSreh
 	bool	is_limit_in_rows; /* ROWS = true, PERCENT = false */
 
 	MemoryContext badrowcontext;	/* per-badrow evaluation context */
-	char	   filename[256];		/* "uri [filename]" */
+	char	   filename[MAXPGPATH];		/* "uri [filename]" */
 
 	bool	log_to_file;		/* or log into file? */
 	Oid		relid;				/* parent relation id */