BUG#16290902 DROP TEMP TABLE IF EXISTS CAN CAUSE POINT

IN TIME RECOVERY FAILURE ON SLAVES

Problem:
DROP TEMP TABLE IF EXISTS commands can cause point
in time recovery (re-applying binlog) failures.

Analyses:
In RBR, 'DROP TEMPORARY TABLE' commands are
always binlogged by adding 'IF EXISTS' clauses.
Also, the slave SQL thread will not check replicate.* filter
rules for "DROP TEMPORARY TABLE IF EXISTS" queries.
If log-slave-updates is enabled on slave, these queries
will be binlogged in the format of "USE `db`;
DROP TEMPORARY TABLE IF EXISTS `t1`;" irrespective
of filtering rules and irrespective of the `db` existence.
When users try to recover slave from it's own binlog,
use `db` command might fail if `db` is not present on slave.

Fix:
At the time of writing the 'DROP TEMPORARY TABLE
IF EXISTS' query into the binlog, 'use `db`' will not be
present and the table name in the query will be a fully
qualified table name.
Eg:
'USE `db`; DROP TEMPORARY TABLE IF EXISTS `t1`;'
will be logged as
'DROP TEMPORARY TABLE IF EXISTS `db`.`t1`;'.

1 files changed, 22 insertions, 5 deletions

diff --git a/sql/sql_table.cc b/sql/sql_table.cc
index c31ba5bb259..ac121572ab2 100644
--- a/sql/sql_table.cc
+++ b/sql/sql_table.cc
@@ -2001,6 +2001,7 @@ int mysql_rm_table_no_locks(THD *thd, TABLE_LIST *tables, bool if_exists,
   bool non_tmp_error= 0;
   bool trans_tmp_table_deleted= 0, non_trans_tmp_table_deleted= 0;
   bool non_tmp_table_deleted= 0;
+  bool is_drop_tmp_if_exists_added= 0;
   String built_query;
   String built_trans_tmp_query, built_non_trans_tmp_query;
   DBUG_ENTER("mysql_rm_table_no_locks");
@@ -2029,6 +2030,15 @@ int mysql_rm_table_no_locks(THD *thd, TABLE_LIST *tables, bool if_exists,
     table stems from the fact that such drop does not commit an ongoing
     transaction and changes to non-transactional tables must be written
     ahead of the transaction in some circumstances.
+
+    6- Slave SQL thread ignores all replicate-* filter rules
+    for temporary tables with 'IF EXISTS' clause. (See sql/sql_parse.cc:
+    mysql_execute_command() for details). These commands will be binlogged
+    as they are, even if the default database (from USE `db`) is not present
+    on the Slave. This can cause point in time recovery failures later
+    when user uses the slave's binlog to re-apply. Hence at the time of binary
+    logging, these commands will be written with fully qualified table names
+    and use `db` will be suppressed.
   */
   if (!dont_log_query)
   {
@@ -2043,6 +2053,7 @@ int mysql_rm_table_no_locks(THD *thd, TABLE_LIST *tables, bool if_exists,
 
     if (thd->is_current_stmt_binlog_format_row() || if_exists)
     {
+      is_drop_tmp_if_exists_added= true;
       built_trans_tmp_query.set_charset(system_charset_info);
       built_trans_tmp_query.append("DROP TEMPORARY TABLE IF EXISTS ");
       built_non_trans_tmp_query.set_charset(system_charset_info);
@@ -2120,10 +2131,12 @@ int mysql_rm_table_no_locks(THD *thd, TABLE_LIST *tables, bool if_exists,
         String *built_ptr_query=
           (is_trans ? &built_trans_tmp_query : &built_non_trans_tmp_query);
         /*
-          Don't write the database name if it is the current one (or if
-          thd->db is NULL).
+          Write the database name if it is not the current one or if
+          thd->db is NULL or 'IF EXISTS' clause is present in 'DROP TEMPORARY'
+          query.
         */
-        if (thd->db == NULL || strcmp(db,thd->db) != 0)
+        if (thd->db == NULL || strcmp(db,thd->db) != 0
+            || is_drop_tmp_if_exists_added )
         {
           append_identifier(thd, built_ptr_query, db, db_len);
           built_ptr_query->append(".");
@@ -2317,7 +2330,9 @@ err:
           error |= thd->binlog_query(THD::STMT_QUERY_TYPE,
                                      built_non_trans_tmp_query.ptr(),
                                      built_non_trans_tmp_query.length(),
-                                     FALSE, FALSE, FALSE, 0);
+                                     FALSE, FALSE,
+                                     is_drop_tmp_if_exists_added,
+                                     0);
       }
       if (trans_tmp_table_deleted)
       {
@@ -2327,7 +2342,9 @@ err:
           error |= thd->binlog_query(THD::STMT_QUERY_TYPE,
                                      built_trans_tmp_query.ptr(),
                                      built_trans_tmp_query.length(),
-                                     TRUE, FALSE, FALSE, 0);
+                                     TRUE, FALSE,
+                                     is_drop_tmp_if_exists_added,
+                                     0);
       }
       if (non_tmp_table_deleted)
       {