BUG#25897: Some queries are no longer possible after a CREATE VIEW

fails

The bug was introduced with the push of the fix for bug#20953: after
the error on view creation we never reset the error state, so some
valid statements would give the same error after that.

The solution is to properly reset the error state.


mysql-test/r/view.result:
  Add result for bug#25897: Some queries are no longer possible after
  a CREATE VIEW fails.
mysql-test/t/view.test:
  Add test case for bug#25897: Some queries are no longer possible after
  a CREATE VIEW fails.
sql/sql_lex.cc:
  Add st_parsing_options::reset() method, call it from lex_start().
sql/sql_lex.h:
  Add st_parsing_options::reset() method, call it from constructor.

mysql-test/r/view.result

@@ -3023,4 +3023,14 @@ SHOW CREATE VIEW v1;
 View	Create View
 v1	CREATE ALGORITHM=UNDEFINED DEFINER=`root`@`localhost` SQL SECURITY DEFINER VIEW `v1` AS select _latin1'The\ZEnd' AS `TheEnd`
 DROP VIEW v1;
+DROP VIEW IF EXISTS v1;
+SELECT * FROM (SELECT 1) AS t;
+1
+1
+CREATE VIEW v1 AS SELECT * FROM (SELECT 1) AS t;
+ERROR HY000: View's SELECT contains a subquery in the FROM clause
+# Previously the following would fail.
+SELECT * FROM (SELECT 1) AS t;
+1
+1
 End of 5.0 tests.

mysql-test/t/view.test

@@ -2975,4 +2975,22 @@ SHOW CREATE VIEW v1;
 
 DROP VIEW v1;
 
+
+#
+# BUG#25897: Some queries are no longer possible after a CREATE VIEW
+# fails 
+#
+--disable_warnings
+DROP VIEW IF EXISTS v1;
+--enable_warnings
+
+let $query = SELECT * FROM (SELECT 1) AS t;
+
+eval $query;
+--error ER_VIEW_SELECT_DERIVED
+eval CREATE VIEW v1 AS $query;
+--echo # Previously the following would fail.
+eval $query;
+
+
 --echo End of 5.0 tests.

sql/sql_lex.cc

@@ -99,6 +99,16 @@ void lex_free(void)
 }
 
 
+void
+st_parsing_options::reset()
+{
+  allows_variable= TRUE;
+  allows_select_into= TRUE;
+  allows_select_procedure= TRUE;
+  allows_derived= TRUE;
+}
+
+
 /*
   This is called before every query that is to be parsed.
   Because of this, it's critical to not do too much things here.
@@ -149,6 +159,7 @@ void lex_start(THD *thd, uchar *buf,uint length)
   lex->safe_to_cache_query= 1;
   lex->time_zone_tables_used= 0;
   lex->leaf_tables_insert= 0;
+  lex->parsing_options.reset();
   lex->empty_field_list_on_rset= 0;
   lex->select_lex.select_number= 1;
   lex->next_state=MY_LEX_START;

sql/sql_lex.h

@@ -866,10 +866,8 @@ struct st_parsing_options
   bool allows_select_procedure;
   bool allows_derived;
 
-  st_parsing_options()
-    : allows_variable(TRUE), allows_select_into(TRUE),
-      allows_select_procedure(TRUE), allows_derived(TRUE)
-  {}
+  st_parsing_options() { reset(); }
+  void reset();
 };