Fix for bug#7915: crash,JOIN VIEW, subquery, SELECT .. FROM INFORMATION_SCHEMA.COLUMNS

mysql-test/r/information_schema.result

@@ -604,3 +604,9 @@ Variable_name	Value
 show global status like "Threads_running";
 Variable_name	Value
 Threads_running	1
+create table t1(f1 int);
+create table t2(f2 int);
+create view v1 as select * from t1, t2;
+set @got_val= (select count(*) from information_schema.columns);
+drop view v1;
+drop table t1, t2;

mysql-test/t/information_schema.test

@@ -352,3 +352,14 @@ show variables where variable_name like "skip_show_databas";
 # Bug #7981:SHOW GLOBAL STATUS crashes server
 #
 show global status like "Threads_running";
+
+#
+# Bug #7915  crash,JOIN VIEW, subquery, 
+# SELECT .. FROM INFORMATION_SCHEMA.COLUMNS
+#
+create table t1(f1 int);
+create table t2(f2 int);
+create view v1 as select * from t1, t2;
+set @got_val= (select count(*) from information_schema.columns);
+drop view v1;
+drop table t1, t2;

sql/sql_lex.cc

@@ -1733,6 +1733,12 @@ bool st_lex::can_not_use_merged()
   {
   case SQLCOM_CREATE_VIEW:
   case SQLCOM_SHOW_CREATE:
+  /*
+    SQLCOM_SHOW_FIELDS is necessary to make 
+    information schema tables working correctly with views.
+    see get_schema_tables_result function
+  */
+  case SQLCOM_SHOW_FIELDS:
     return TRUE;
   default:
     return FALSE;