Merge pull request #1261 from robertbindar/mdev-17978

MDEV-17978 Server crash in SHOW CREATE SEQUENCE on a broken view

mysql-test/suite/sql_sequence/view.result

@@ -24,3 +24,13 @@ ERROR 42S02: 'test.v1' is not a SEQUENCE
 SELECT PREVIOUS VALUE FOR v1;
 ERROR 42S02: 'test.v1' is not a SEQUENCE
 drop view v1;
+#
+# MDEV 17978 Server crashes in mysqld_show_create_get_fields
+# upon SHOW CREATE SEQUENCE on a broken view
+#
+CREATE TABLE t1 (a INT);
+CREATE VIEW v1 AS SELECT * FROM t1;
+DROP TABLE t1;
+SHOW CREATE SEQUENCE v1;
+ERROR 42S02: 'test.v1' is not a SEQUENCE
+DROP VIEW v1;

mysql-test/suite/sql_sequence/view.test

@@ -27,3 +27,14 @@ SELECT NEXT VALUE FOR v1;
 --error ER_NOT_SEQUENCE
 SELECT PREVIOUS VALUE FOR v1;
 drop view v1;
+
+--echo #
+--echo # MDEV 17978 Server crashes in mysqld_show_create_get_fields
+--echo # upon SHOW CREATE SEQUENCE on a broken view
+--echo #
+CREATE TABLE t1 (a INT);
+CREATE VIEW v1 AS SELECT * FROM t1;
+DROP TABLE t1;
+--error ER_NOT_SEQUENCE
+SHOW CREATE SEQUENCE v1;
+DROP VIEW v1;

sql/sql_show.cc

@@ -1316,7 +1316,8 @@ mysqld_show_create_get_fields(THD *thd, TABLE_LIST *table_list,
     goto exit;
   }
   else if (lex->table_type == TABLE_TYPE_SEQUENCE &&
-           table_list->table->s->table_type != TABLE_TYPE_SEQUENCE)
+           (!table_list->table ||
+            table_list->table->s->table_type != TABLE_TYPE_SEQUENCE))
   {
     my_error(ER_NOT_SEQUENCE, MYF(0),
              table_list->db.str, table_list->table_name.str);