A patch for Bug#11763166 (55847: SHOW WARNINGS returns empty

result set when SQLEXCEPTION is active.

The problem was in a hackish THD::no_warnings_for_error attribute.
When it was set, an error was not written to Warning_info -- only
Diagnostics_area state was changed. That means, Diagnostics_area
might contain error state, which is not present in Warning_info.

The user-visible problem was that in some cases SHOW WARNINGS
returned empty result set (i.e. there were no warnings) while
the previous SQL statement failed. According to the MySQL
protocol errors must be presented in warning list.

The main idea of this patch is to remove THD::no_warnings_for_error.
There were few places where it was used:
  - sql_admin.cc, handling of REPAIR TABLE USE_FRM.
  - sql_show.cc, when calling fill_schema_table_from_frm().
  - sql_show.cc, when calling fill_table().
The fix is to either use internal-error-handlers, or to use
temporary Warning_info storing warnings, which might be ignored.

This patch is needed to fix Bug 11763162 (55843).

1 files changed, 35 insertions, 10 deletions

diff --git a/sql/sql_admin.cc b/sql/sql_admin.cc
index dea8d38938c..575991211e6 100644
--- a/sql/sql_admin.cc
+++ b/sql/sql_admin.cc
@@ -263,7 +263,7 @@ static bool mysql_admin_table(THD* thd, TABLE_LIST* tables,
                               const char *operator_name,
                               thr_lock_type lock_type,
                               bool open_for_modify,
-                              bool no_warnings_for_error,
+                              bool repair_table_use_frm,
                               uint extra_open_options,
                               int (*prepare_func)(THD *, TABLE_LIST *,
                                                   HA_CHECK_OPT *),
@@ -331,18 +331,43 @@ static bool mysql_admin_table(THD* thd, TABLE_LIST* tables,
       lex->query_tables= table;
       lex->query_tables_last= &table->next_global;
       lex->query_tables_own_last= 0;
-      /*
-        Under locked tables, we know that the table can be opened,
-        so any errors opening the table are logical errors.
-        In these cases it makes sense to report them.
-      */
-      if (!thd->locked_tables_mode)
-        thd->no_warnings_for_error= no_warnings_for_error;
+
       if (view_operator_func == NULL)
         table->required_type=FRMTYPE_TABLE;
 
-      open_error= open_and_lock_tables(thd, table, TRUE, 0);
-      thd->no_warnings_for_error= 0;
+      if (!thd->locked_tables_mode && repair_table_use_frm)
+      {
+        /*
+          If we're not under LOCK TABLES and we're executing REPAIR TABLE
+          USE_FRM, we need to ignore errors from open_and_lock_tables().
+          REPAIR TABLE USE_FRM is a heavy weapon used when a table is
+          critically damaged, so open_and_lock_tables() will most likely
+          report errors. Those errors are not interesting for the user
+          because it's already known that the table is badly damaged.
+        */
+
+        Warning_info wi(thd->query_id, false);
+        Warning_info *wi_saved= thd->warning_info;
+
+        thd->warning_info= &wi;
+
+        open_error= open_and_lock_tables(thd, table, TRUE, 0);
+
+        thd->warning_info= wi_saved;
+      }
+      else
+      {
+        /*
+          It's assumed that even if it is REPAIR TABLE USE_FRM, the table
+          can be opened if we're under LOCK TABLES (otherwise LOCK TABLES
+          would fail). Thus, the only errors we could have from
+          open_and_lock_tables() are logical ones, like incorrect locking
+          mode. It does make sense for the user to see such errors.
+        */
+
+        open_error= open_and_lock_tables(thd, table, TRUE, 0);
+      }
+
       table->next_global= save_next_global;
       table->next_local= save_next_local;
       thd->open_options&= ~extra_open_options;