BUG#45516 SQL thread does not use database charset properly

  
Replication SQL thread does not set database default charset to 
thd->variables.collation_database properly, when executing LOAD DATA binlog.
This bug can be repeated by using "LOAD DATA" command in STATEMENT mode.
  
This patch adds code to find the default character set of the current database 
then assign it to thd->db_charset when slave server begins to execute a relay log.
The test of this bug is added into rpl_loaddata_charset.test 

mysql-test/include/rpl_loaddata_charset.inc

+connection master;
+--disable_warnings
+DROP DATABASE IF EXISTS mysqltest;
+--enable_warnings
+
+CREATE DATABASE mysqltest CHARSET UTF8;
+USE mysqltest;
+CREATE TABLE t (cl varchar(100)) CHARSET UTF8;
+
+if (!$LOAD_LOCAL)
+{
+  LOAD DATA INFILE '../std_data_ln/loaddata_utf8.dat' INTO TABLE t
+  FIELDS TERMINATED BY ',' LINES TERMINATED BY '\n';
+}
+if ($LOAD_LOCAL)
+{
+  LOAD DATA LOCAL INFILE './std_data/loaddata_utf8.dat' INTO TABLE t
+  FIELDS TERMINATED BY ',' LINES TERMINATED BY '\n';
+}
+
+save_master_pos;
+echo ----------content on master----------;
+SELECT hex(cl) FROM t;
+
+connection slave;
+sync_with_master;
+echo ----------content on slave----------;
+USE mysqltest;
+SELECT hex(cl) FROM t;
+
+connection master;
+DROP DATABASE mysqltest;
+save_master_pos;
+connection slave;
+sync_with_master;

mysql-test/r/rpl_loaddata_charset.result

@@ -35,3 +35,44 @@ C3BF
 D0AA
 D0AA
 drop table t1;
+-------------test bug#45516------------------
+DROP DATABASE IF EXISTS mysqltest;
+CREATE DATABASE mysqltest CHARSET UTF8;
+USE mysqltest;
+CREATE TABLE t (cl varchar(100)) CHARSET UTF8;
+LOAD DATA LOCAL INFILE './std_data/loaddata_utf8.dat' INTO TABLE t
+FIELDS TERMINATED BY ',' LINES TERMINATED BY '\n';
+----------content on master----------
+SELECT hex(cl) FROM t;
+hex(cl)
+E4B880E4BA8CE4B889
+E59B9BE4BA94E585AD
+E4B883E585ABE4B99D
+----------content on slave----------
+USE mysqltest;
+SELECT hex(cl) FROM t;
+hex(cl)
+E4B880E4BA8CE4B889
+E59B9BE4BA94E585AD
+E4B883E585ABE4B99D
+DROP DATABASE mysqltest;
+DROP DATABASE IF EXISTS mysqltest;
+CREATE DATABASE mysqltest CHARSET UTF8;
+USE mysqltest;
+CREATE TABLE t (cl varchar(100)) CHARSET UTF8;
+LOAD DATA INFILE '../std_data_ln/loaddata_utf8.dat' INTO TABLE t
+FIELDS TERMINATED BY ',' LINES TERMINATED BY '\n';
+----------content on master----------
+SELECT hex(cl) FROM t;
+hex(cl)
+E4B880E4BA8CE4B889
+E59B9BE4BA94E585AD
+E4B883E585ABE4B99D
+----------content on slave----------
+USE mysqltest;
+SELECT hex(cl) FROM t;
+hex(cl)
+E4B880E4BA8CE4B889
+E59B9BE4BA94E585AD
+E4B883E585ABE4B99D
+DROP DATABASE mysqltest;

mysql-test/std_data/loaddata_utf8.dat

+一二三
+四五六
+七八九

mysql-test/t/rpl_loaddata_charset.test

@@ -31,3 +31,20 @@ select hex(a) from t1;
 connection master;
 drop table t1;
 sync_slave_with_master;
+
+#
+# Bug#45516 
+#   When slave SQL thread executing LOAD DATA command, the
+#   thd->variables.collation_database was not set properly to the default
+#   database charset
+#
+
+echo -------------test bug#45516------------------;
+
+# LOAD DATA INFILE
+let $LOAD_LOCAL=1;
+source include/rpl_loaddata_charset.inc;
+
+# LOAD DATA LOCAL INFILE
+let $LOAD_LOCAL=0;
+source include/rpl_loaddata_charset.inc;

sql/log_event.cc

@@ -1918,6 +1918,8 @@ int Query_log_event::exec_event(struct st_relay_log_info* rli,
 {
   const char *new_db= rewrite_db(db);
   int expected_error,actual_error= 0;
+  HA_CREATE_INFO db_options;
+
   /*
     Colleagues: please never free(thd->catalog) in MySQL. This would lead to
     bugs as here thd->catalog is a part of an alloced block, not an entire
@@ -1926,6 +1928,13 @@ int Query_log_event::exec_event(struct st_relay_log_info* rli,
   */
   thd->catalog= catalog_len ? (char *) catalog : (char *)"";
   thd->set_db(new_db, (uint) strlen(new_db));          /* allocates a copy of 'db' */
+
+  /*
+    Setting the character set and collation of the current database thd->db.
+   */
+  load_db_opt_by_name(thd, thd->db, &db_options);
+  if (db_options.default_table_charset)
+    thd->db_charset= db_options.default_table_charset;
   thd->variables.auto_increment_increment= auto_increment_increment;
   thd->variables.auto_increment_offset=    auto_increment_offset;