A backport of patch for Bug#26704.

Original revision is from mysql-6.0-codebase:

revno: 2630.3.1
committer: Alexander Nozdrin <alik@mysql.com>
branch nick: 6.0-rt-bug26704
timestamp: Thu 2008-05-29 21:04:06 +0400
message:
  A fix for Bug#26704: Failing DROP DATABASE brings
  mysql-client out of sync.

  The problem was that we changed current database w/o caring
  whether it was dropped successfully or not.

  The fix is not to change current database if we failed to drop it.

mysql-test/r/drop-no_root.result

@@ -0,0 +1,27 @@
+
+# --
+# -- Bug#26704: Failing DROP DATABASE brings mysql-client out of sync.
+# --
+
+DROP DATABASE IF EXISTS mysql_test;
+
+CREATE DATABASE mysql_test;
+CREATE TABLE mysql_test.t1(c INT);
+use mysql_test;
+
+chmod 000 mysql_test/t1.frm
+
+DROP DATABASE mysql_test;
+ERROR HY000: Error dropping database (can't rmdir './mysql_test', errno: 39)
+
+SELECT DATABASE();
+DATABASE()
+mysql_test
+
+rm mysql_test/t1.MYD mysql_test/t1.MYI
+
+DROP DATABASE mysql_test;
+
+use test;
+
+# -- End of Bug#26704.

mysql-test/t/drop-no_root.test

@@ -0,0 +1,49 @@
+# This test uses chmod, can't be run with root permissions
+--source include/not_as_root.inc
+
+###########################################################################
+
+--echo
+--echo # --
+--echo # -- Bug#26704: Failing DROP DATABASE brings mysql-client out of sync.
+--echo # --
+
+--echo
+--disable_warnings
+DROP DATABASE IF EXISTS mysql_test;
+--enable_warnings
+
+--echo
+CREATE DATABASE mysql_test;
+CREATE TABLE mysql_test.t1(c INT);
+
+use mysql_test;
+
+let $MYSQLD_DATADIR= `select @@datadir`;
+
+--echo
+--echo chmod 000 mysql_test/t1.frm
+--chmod 0000 $MYSQLD_DATADIR/mysql_test/t1.frm
+
+--echo
+--error ER_DB_DROP_RMDIR
+DROP DATABASE mysql_test;
+
+--echo
+SELECT DATABASE();
+
+--echo
+--echo rm mysql_test/t1.MYD mysql_test/t1.MYI
+--exec rm $MYSQLD_DATADIR/mysql_test/t1.MYD
+--exec rm $MYSQLD_DATADIR/mysql_test/t1.MYI
+
+--echo
+DROP DATABASE mysql_test;
+
+--echo
+use test;
+
+--echo
+--echo # -- End of Bug#26704.
+
+###########################################################################

sql/sql_db.cc

@@ -1027,7 +1027,7 @@ exit:
     SELECT DATABASE() in the future). For this we free() thd->db and set
     it to 0.
   */
-  if (thd->db && !strcmp(thd->db, db))
+  if (thd->db && !strcmp(thd->db, db) && error == 0)
     mysql_change_db_impl(thd, NULL, 0, thd->variables.collation_server);
   VOID(pthread_mutex_unlock(&LOCK_mysql_create_db));
   start_waiting_global_read_lock(thd);