disallow explain refresh matview stmt

src/common/backend/parser/gram.y

@@ -12817,7 +12817,6 @@ ExplainableStmt:
 			| DeclareCursorStmt
 			| CreateAsStmt
 			| CreateMatViewStmt
-			| RefreshMatViewStmt
 			| ExecuteStmt					/* by default all are $$=$1 */
 		;
 

src/test/regress/expected/matview.out

@@ -28,6 +28,11 @@ EXPLAIN (analyze on, costs off)
 --? Total runtime: .* ms
 (4 rows)
 
+EXPLAIN (analyze on, costs off)
+  REFRESH MATERIALIZED VIEW mvtest_tm;
+ERROR:  syntax error at or near "REFRESH"
+LINE 2:   REFRESH MATERIALIZED VIEW mvtest_tm;
+          ^
 SELECT * FROM mvtest_tm ORDER BY type;
  type | totamt 
 ------+--------

src/test/regress/sql/matview.sql

@@ -14,6 +14,8 @@ SELECT * FROM mvtest_tv ORDER BY type;
 -- create a materialized view with no data, and confirm correct behavior
 EXPLAIN (analyze on, costs off)
   CREATE MATERIALIZED VIEW mvtest_tm AS SELECT type, sum(amt) AS totamt FROM mvtest_t GROUP BY type WITH NO DATA;
+EXPLAIN (analyze on, costs off)
+  REFRESH MATERIALIZED VIEW mvtest_tm;
 SELECT * FROM mvtest_tm ORDER BY type;
 REFRESH MATERIALIZED VIEW mvtest_tm;
 ALTER MATERIALIZED VIEW mvtest_tm set (orientation=column); --error