BUG#34656 - KILL a query = Assertion failed: m_status == DA_ERROR ||

m_status == DA_OK

Reading from information_scema.tables or information_schema.columns
may cause assertion failure in debug builds. This may happen under
rare circumstances when information_schema fails to get information
about a table (e.g. when a connection is killed).

This happens because open_normal_and_derived_tables() can return an
error without setting an error message in THD. But information_schema
attempts to get an error message from THD unconditionally.

With this fix information_schema attempts to get an error message
from THD only in case error message is set in THD.

mysql-test/r/information_schema.result

@@ -1638,4 +1638,6 @@ show open tables where f1()=0;
 show open tables where f1()=0;
 drop table t1;
 drop function f1;
+select * from information_schema.tables where 1=sleep(100000);
+select * from information_schema.columns where 1=sleep(100000);
 End of 5.1 tests.

mysql-test/t/information_schema.test

@@ -1270,4 +1270,48 @@ show open tables where f1()=0;
 drop table t1;
 drop function f1;
 
+#
+# BUG#34656 - KILL a query = Assertion failed: m_status == DA_ERROR ||
+#             m_status == DA_OK
+#
+connect (conn1, localhost, root,,);
+connection conn1;
+let $ID= `select connection_id()`;
+send select * from information_schema.tables where 1=sleep(100000);
+connection default;
+let $wait_timeout= 10;
+let $wait_condition=select count(*)=1 from information_schema.processlist
+where state='User sleep' and
+info='select * from information_schema.tables where 1=sleep(100000)';
+--source include/wait_condition.inc
+disable_query_log;
+eval kill $ID;
+enable_query_log;
+disconnect conn1;
+let $wait_timeout= 10;
+let $wait_condition=select count(*)=0 from information_schema.processlist
+where state='User sleep' and
+info='select * from information_schema.tables where 1=sleep(100000)';
+--source include/wait_condition.inc
+
+connect (conn1, localhost, root,,);
+connection conn1;
+let $ID= `select connection_id()`;
+send select * from information_schema.columns where 1=sleep(100000);
+connection default;
+let $wait_timeout= 10;
+let $wait_condition=select count(*)=1 from information_schema.processlist
+where state='User sleep' and
+info='select * from information_schema.columns where 1=sleep(100000)';
+--source include/wait_condition.inc
+disable_query_log;
+eval kill $ID;
+enable_query_log;
+disconnect conn1;
+let $wait_timeout= 10;
+let $wait_condition=select count(*)=0 from information_schema.processlist
+where state='User sleep' and
+info='select * from information_schema.columns where 1=sleep(100000)';
+--source include/wait_condition.inc
+
 --echo End of 5.1 tests.

sql/item_func.cc

@@ -3722,6 +3722,7 @@ longlong Item_func_sleep::val_int()
   pthread_cond_init(&cond, NULL);
   pthread_mutex_lock(&LOCK_user_locks);
 
+  thd_proc_info(thd, "User sleep");
   thd->mysys_var->current_mutex= &LOCK_user_locks;
   thd->mysys_var->current_cond=  &cond;
 
@@ -3733,6 +3734,7 @@ longlong Item_func_sleep::val_int()
       break;
     error= 0;
   }
+  thd_proc_info(thd, 0);
   pthread_mutex_unlock(&LOCK_user_locks);
   pthread_mutex_lock(&thd->mysys_var->mutex);
   thd->mysys_var->current_mutex= 0;

sql/sql_show.cc

@@ -3430,7 +3430,7 @@ static int get_schema_tables_record(THD *thd, TABLE_LIST *tables,
     /*
       there was errors during opening tables
     */
-    const char *error= thd->main_da.message();
+    const char *error= thd->is_error() ? thd->main_da.message() : "";
     if (tables->view)
       table->field[3]->store(STRING_WITH_LEN("VIEW"), cs);
     else if (tables->schema_table)
@@ -3631,8 +3631,9 @@ static int get_schema_column_record(THD *thd, TABLE_LIST *tables,
         I.e. we are in SELECT FROM INFORMATION_SCHEMA.COLUMS
         rather than in SHOW COLUMNS
       */ 
-      push_warning(thd, MYSQL_ERROR::WARN_LEVEL_WARN,
+      if (thd->is_error())
-                   thd->main_da.sql_errno(), thd->main_da.message());
+        push_warning(thd, MYSQL_ERROR::WARN_LEVEL_WARN,
+                     thd->main_da.sql_errno(), thd->main_da.message());
       thd->clear_error();
       res= 0;
     }