BUG#41725: slave crashes when inserting into temporary table after

stop/start slave
      
When stopping and restarting the slave while it is replicating
temporary tables, the server would crash or raise an assertion
failure. This was due to the fact that although temporary tables are
saved between slave threads restart, the reference to the thread in
use (table->in_use) was not being properly updated when the restart
happened (it would still reference the old/invalid thread instead of
the new one).
      
This patch addresses this issue by resetting the reference to the new
slave thread on slave thread restart.

mysql-test/r/rpl_temporary.result:
  Result file.
mysql-test/t/rpl_temporary.test:
  Test case that checks that both failures go away.
sql/slave.cc:
  Changed slave.cc to reset sql_thd reference in temporary tables.

mysql-test/r/rpl_temporary.result

@@ -133,3 +133,22 @@ select * from t1;
 a
 1
 drop table t1;
+DROP TABLE IF EXISTS t1;
+CREATE TEMPORARY TABLE t1 (a char(1));
+INSERT INTO t1 VALUES ('a');
+include/stop_slave.inc
+include/start_slave.inc
+INSERT INTO t1 VALUES ('b');
+DROP TABLE IF EXISTS t1;
+CREATE TEMPORARY TABLE `t1`(`a` tinyint,`b` char(1))engine=myisam;
+INSERT INTO `t1` set `a`=128,`b`='128';
+Warnings:
+Warning	1264	Out of range value adjusted for column 'a' at row 1
+Warning	1265	Data truncated for column 'b' at row 1
+include/stop_slave.inc
+include/start_slave.inc
+INSERT INTO `t1` set `a`=128,`b`='128';
+Warnings:
+Warning	1264	Out of range value adjusted for column 'a' at row 1
+Warning	1265	Data truncated for column 'b' at row 1
+DROP TABLE t1;

mysql-test/t/rpl_temporary.test

@@ -217,4 +217,74 @@ drop table t1;
 # Delete the anonymous users
 source include/delete_anonymous_users.inc;
 
+# ##################################################################
+# BUG#41725: slave crashes when inserting into temporary table after
+#            stop/start slave
+#
+#  This test checks that both reported issues (assertion failure and
+#  crash) go away. It is implemented as follows:
+#    
+#    case 1: assertion failure
+#      i) create and insert into temporary table on master
+#     ii) sync slave with master
+#    iii) stop and restart slave
+#     iv) insert into master another value
+#      v) sync slave with master
+#
+#
+#    case 2: crash (SIGSEV)
+#      i) create and insert into temporary table on master (insert
+#         produces warnings)
+#     ii) sync slave with master
+#    iii) stop and restart slave
+#     iv) insert into master more values
+#      v) sync slave with master
+
+# case 1: Assertion in Field_string::store() failed because current 
+#         thread reference differed from table->in_use after slave 
+#         restart
+
+connection master;
+
+disable_warnings;
+DROP TABLE IF EXISTS t1;
+enable_warnings;
+
+CREATE TEMPORARY TABLE t1 (a char(1));
+INSERT INTO t1 VALUES ('a');
+sync_slave_with_master;
+
+source include/stop_slave.inc;
+source include/start_slave.inc;
+
+connection master;
+INSERT INTO t1 VALUES ('b');
+sync_slave_with_master;
+
+# case 2: crash on sp_rcontext::find_handler because it used 
+#         reference to invalid THD object after slave restart
+
+connection master;
+
+disable_warnings;
+DROP TABLE IF EXISTS t1;
+enable_warnings;
+CREATE TEMPORARY TABLE `t1`(`a` tinyint,`b` char(1))engine=myisam;
+INSERT INTO `t1` set `a`=128,`b`='128';
+
+sync_slave_with_master;
+
+source include/stop_slave.inc;
+source include/start_slave.inc;
+
+connection master;
+INSERT INTO `t1` set `a`=128,`b`='128';
+sync_slave_with_master;
+
+# cleanup
+
+connection master;
+DROP TABLE t1;
+sync_slave_with_master;
+
 # End of 5.0 tests

sql/slave.cc

@@ -545,6 +545,14 @@ void st_relay_log_info::close_temporary_tables()
   slave_open_temp_tables= 0;
 }
 
+static void set_thd_in_use_temporary_tables(RELAY_LOG_INFO *rli)
+{
+  TABLE *table;
+
+  for (table= rli->save_temporary_tables ; table ; table= table->next)
+    table->in_use= rli->sql_thd;
+}
+
 /*
   purge_relay_logs()
 
@@ -3964,6 +3972,7 @@ pthread_handler_t handle_slave_sql(void *arg)
   }
   thd->init_for_queries();
   thd->temporary_tables = rli->save_temporary_tables; // restore temp tables
+  set_thd_in_use_temporary_tables(rli);   // (re)set sql_thd in use for saved temp tables
   pthread_mutex_lock(&LOCK_thread_count);
   threads.append(thd);
   pthread_mutex_unlock(&LOCK_thread_count);
@@ -4136,6 +4145,7 @@ the slave SQL thread with \"SLAVE START\". We stopped at log \
   DBUG_ASSERT(rli->sql_thd == thd);
   THD_CHECK_SENTRY(thd);
   rli->sql_thd= 0;
+  set_thd_in_use_temporary_tables(rli);  // (re)set sql_thd in use for saved temp tables
   pthread_mutex_lock(&LOCK_thread_count);
   THD_CHECK_SENTRY(thd);
   delete thd;