Fix for BUG#25843: changing default database between PREPARE and EXECUTE

of statement breaks binlog.

There were two problems discovered by this bug:

  1. Default (current) database is not fixed at the creation time.
     That leads to wrong output of DATABASE() function.

  2. Database attributes (@@collation_database) are not fixed at
     the creation time. That leads to wrong resultset.

Binlog breakage and Query Cache wrong output happened because of
the first problem.

The fix is to remember the current database at the PREPARE-time and
set it each time at EXECUTE.

mysql-test/include/query_cache_sql_prepare.inc

@@ -275,5 +275,223 @@ drop table t1;
 --echo ---- disconnect connection con1 ----
 disconnect con1;
 
+#
+# Bug #25843 Changing default database between PREPARE and EXECUTE of statement
+# breaks binlog.
+#
+# There were actually two problems discovered by this bug:
+#
+#   1. Default (current) database is not fixed at the creation time.
+#      That leads to wrong output of DATABASE() function.
+#
+#   2. Database attributes (@@collation_database) are not fixed at the creation
+#      time. That leads to wrong resultset.
+#
+# Binlog breakage and Query Cache wrong output happened because of the first
+# problem.
+#
+
+--echo ########################################################################
+--echo #
+--echo # BUG#25843: Changing default database between PREPARE and EXECUTE of
+--echo # statement breaks binlog.
+--echo #
+--echo ########################################################################
+
+###############################################################################
+
+--echo
+--echo #
+--echo # Check that default database and its attributes are fixed at the
+--echo # creation time.
+--echo #
+
+# Prepare data structures.
+
+--echo
+--disable_warnings
+DROP DATABASE IF EXISTS mysqltest1;
+DROP DATABASE IF EXISTS mysqltest2;
+--enable_warnings
+
+--echo
+CREATE DATABASE mysqltest1 COLLATE utf8_unicode_ci;
+CREATE DATABASE mysqltest2 COLLATE utf8_general_ci;
+
+--echo
+CREATE TABLE mysqltest1.t1(msg VARCHAR(255));
+CREATE TABLE mysqltest2.t1(msg VARCHAR(255));
+
+# - Create a prepared statement with mysqltest1 as default database;
+
+--echo
+
+use mysqltest1;
+
+PREPARE stmt_a_1 FROM 'INSERT INTO t1 VALUES(DATABASE())';
+PREPARE stmt_a_2 FROM 'INSERT INTO t1 VALUES(@@collation_database)';
+
+# - Execute on mysqltest1.
+
+--echo
+
+EXECUTE stmt_a_1;
+EXECUTE stmt_a_2;
+
+# - Execute on mysqltest2.
+
+--echo
+
+use mysqltest2;
+
+EXECUTE stmt_a_1;
+EXECUTE stmt_a_2;
+
+# - Check the results;
+
+--echo
+SELECT * FROM mysqltest1.t1;
+
+--echo
+SELECT * FROM mysqltest2.t1;
+
+# - Drop prepared statements.
+
+--echo
+DROP PREPARE stmt_a_1;
+DROP PREPARE stmt_a_2;
+
+###############################################################################
+
+--echo
+--echo #
+--echo # The Query Cache test case.
+--echo #
+
+--echo
+DELETE FROM mysqltest1.t1;
+DELETE FROM mysqltest2.t1;
+
+--echo
+INSERT INTO mysqltest1.t1 VALUES('mysqltest1.t1');
+INSERT INTO mysqltest2.t1 VALUES('mysqltest2.t1');
+
+--echo
+use mysqltest1;
+PREPARE stmt_b_1 FROM 'SELECT * FROM t1';
+
+--echo
+use mysqltest2;
+PREPARE stmt_b_2 FROM 'SELECT * FROM t1';
+
+--echo
+EXECUTE stmt_b_1;
+
+--echo
+EXECUTE stmt_b_2;
+
+--echo
+use mysqltest1;
+
+--echo
+EXECUTE stmt_b_1;
+
+--echo
+EXECUTE stmt_b_2;
+
+--echo
+DROP PREPARE stmt_b_1;
+DROP PREPARE stmt_b_2;
+
+# Cleanup.
+
+--echo
+use test;
+
+--echo
+DROP DATABASE mysqltest1;
+DROP DATABASE mysqltest2;
+
+###############################################################################
+
+--echo
+--echo #
+--echo # Check that prepared statements work properly when there is no current
+--echo # database.
+--echo #
+
+--echo
+CREATE DATABASE mysqltest1 COLLATE utf8_unicode_ci;
+CREATE DATABASE mysqltest2 COLLATE utf8_general_ci;
+
+--echo
+use mysqltest1;
+
+--echo
+PREPARE stmt_c_1 FROM 'SELECT DATABASE(), @@collation_database';
+
+--echo
+use mysqltest2;
+
+--echo
+PREPARE stmt_c_2 FROM 'SELECT DATABASE(), @@collation_database';
+
+--echo
+DROP DATABASE mysqltest2;
+
+--echo
+SELECT DATABASE(), @@collation_database;
+
+# -- Here we have: current db: NULL; stmt db: mysqltest1;
+--echo
+EXECUTE stmt_c_1;
+
+--echo
+SELECT DATABASE(), @@collation_database;
+
+# -- Here we have: current db: NULL; stmt db: mysqltest2 (non-existent);
+--echo
+EXECUTE stmt_c_2;
+
+--echo
+SELECT DATABASE(), @@collation_database;
+
+# -- Create prepared statement, which has no current database.
+
+--echo
+PREPARE stmt_c_3 FROM 'SELECT DATABASE(), @@collation_database';
+
+# -- Here we have: current db: NULL; stmt db: NULL;
+--echo
+EXECUTE stmt_c_3;
+
+--echo
+use mysqltest1;
+
+# -- Here we have: current db: mysqltest1; stmt db: mysqltest2 (non-existent);
+--echo
+EXECUTE stmt_c_2;
+
+--echo
+SELECT DATABASE(), @@collation_database;
+
+# -- Here we have: current db: mysqltest1; stmt db: NULL;
+--echo
+EXECUTE stmt_c_3;
+
+--echo
+SELECT DATABASE(), @@collation_database;
+
+--echo
+DROP DATABASE mysqltest1;
+
+--echo
+use test;
+
+--echo
+--echo ########################################################################
+
+###############################################################################
+
 set @@global.query_cache_size=@initial_query_cache_size;
 flush status; # reset Qcache status variables for next tests