From 909f7607018e644754a2c41b791b44b25a05e8fb Mon Sep 17 00:00:00 2001
From: Sergey Vojtovich <svoj@mariadb.org>
Date: Mon, 15 Jun 2015 15:37:14 +0400
Subject: [PATCH] MDEV-5309 - RENAME TABLE does not check for existence of the
 table's engine

When RENAME TABLE is executed, it apparently does not check whether the engine
is available (unlike ALTER TABLE .. RENAME, which does). It means that if the
engine in question was not loaded on some reason, the table might become
unusable, since the engine won't know about the change.

With this patch RENAME TABLE fails if storage engine is not available.
---
 mysql-test/r/plugin.result | 10 ++++++++++
 mysql-test/t/plugin.test   | 11 +++++++++++
 sql/sql_rename.cc          |  9 ++-------
 sql/sql_table.cc           |  4 ++--
 4 files changed, 25 insertions(+), 9 deletions(-)

diff --git a/mysql-test/r/plugin.result b/mysql-test/r/plugin.result
index 630f0141d18..3a2bb32b13d 100644
--- a/mysql-test/r/plugin.result
+++ b/mysql-test/r/plugin.result
@@ -321,3 +321,13 @@ UNUSABLE
 uninstall soname 'ha_example';
 select plugin_name from information_schema.plugins where plugin_library like 'ha_example%';
 plugin_name
+#
+# MDEV-5309 - RENAME TABLE does not check for existence of the table's
+#             engine
+#
+INSTALL PLUGIN example SONAME 'ha_example';
+CREATE TABLE t1(a INT) ENGINE=EXAMPLE;
+UNINSTALL PLUGIN example;
+RENAME TABLE t1 TO t2;
+ERROR 42S02: Table 'test.t1' doesn't exist
+DROP TABLE t1;
diff --git a/mysql-test/t/plugin.test b/mysql-test/t/plugin.test
index 0655aff9fc9..9c2a408b612 100644
--- a/mysql-test/t/plugin.test
+++ b/mysql-test/t/plugin.test
@@ -252,3 +252,14 @@ select plugin_name from information_schema.plugins where plugin_library like 'ha
 uninstall soname 'ha_example';
 select plugin_name from information_schema.plugins where plugin_library like 'ha_example%';
 
+
+--echo #
+--echo # MDEV-5309 - RENAME TABLE does not check for existence of the table's
+--echo #             engine
+--echo #
+INSTALL PLUGIN example SONAME 'ha_example';
+CREATE TABLE t1(a INT) ENGINE=EXAMPLE;
+UNINSTALL PLUGIN example;
+--error ER_NO_SUCH_TABLE
+RENAME TABLE t1 TO t2;
+DROP TABLE t1;
diff --git a/sql/sql_rename.cc b/sql/sql_rename.cc
index 2c17898f07c..6496e1895fb 100644
--- a/sql/sql_rename.cc
+++ b/sql/sql_rename.cc
@@ -238,7 +238,6 @@ do_rename(THD *thd, TABLE_LIST *ren_table, char *new_db, char *new_table_name,
 {
   int rc= 1;
   handlerton *hton;
-  bool new_exists, old_exists;
   const char *new_alias, *old_alias;
   DBUG_ENTER("do_rename");
 
@@ -254,17 +253,13 @@ do_rename(THD *thd, TABLE_LIST *ren_table, char *new_db, char *new_table_name,
   }
   DBUG_ASSERT(new_alias);
 
-  new_exists= ha_table_exists(thd, new_db, new_alias);
-
-  if (new_exists)
+  if (ha_table_exists(thd, new_db, new_alias))
   {
     my_error(ER_TABLE_EXISTS_ERROR, MYF(0), new_alias);
     DBUG_RETURN(1);                     // This can't be skipped
   }
 
-  old_exists= ha_table_exists(thd, ren_table->db, old_alias, &hton);
-
-  if (old_exists)
+  if (ha_table_exists(thd, ren_table->db, old_alias, &hton) && hton)
   {
     DBUG_ASSERT(!thd->locked_tables_mode);
     tdc_remove_table(thd, TDC_RT_REMOVE_ALL,
diff --git a/sql/sql_table.cc b/sql/sql_table.cc
index 6ee0e9bc871..c31a6fd6474 100644
--- a/sql/sql_table.cc
+++ b/sql/sql_table.cc
@@ -5149,6 +5149,7 @@ mysql_rename_table(handlerton *base, const char *old_db,
   ulonglong save_bits= thd->variables.option_bits;
   int length;
   DBUG_ENTER("mysql_rename_table");
+  DBUG_ASSERT(base);
   DBUG_PRINT("enter", ("old: '%s'.'%s'  new: '%s'.'%s'",
                        old_db, old_name, new_db, new_name));
 
@@ -5156,8 +5157,7 @@ mysql_rename_table(handlerton *base, const char *old_db,
   if (flags & NO_FK_CHECKS) 
     thd->variables.option_bits|= OPTION_NO_FOREIGN_KEY_CHECKS;
 
-  file= (base == NULL ? 0 :
-         get_new_handler((TABLE_SHARE*) 0, thd->mem_root, base));
+  file= get_new_handler((TABLE_SHARE*) 0, thd->mem_root, base);
 
   build_table_filename(from, sizeof(from) - 1, old_db, old_name, "",
                        flags & FN_FROM_IS_TMP);