MDEV-4591:Setting gtid* values from inside a transaction might cause unexpected results

Now we give an error on attempts to set @@SESSION.gtid_domain_id or
@@SESSION.gtid_seq_no when a transaction is active.

mysql-test/suite/rpl/r/rpl_gtid_errorhandling.result

@@ -29,6 +29,29 @@ include/start_slave.inc
 SELECT * FROM t1;
 a
 1
+*** Test that setting @@gtid_domain_id or @@gtid_seq_no is not allowed inside a transaction. ***
+BEGIN;
+INSERT INTO t1 VALUES (100);
+SET SESSION gtid_domain_id= 100;
+ERROR HY000: Cannot modify @@session.gtid_domain_id or @@session.gtid_seq_no inside a transaction
+SET SESSION gtid_seq_no= 100;
+ERROR HY000: Cannot modify @@session.gtid_domain_id or @@session.gtid_seq_no inside a transaction
+SET @old_domain= @@GLOBAL.gtid_domain_id;
+SET GLOBAL gtid_domain_id= 100;
+SELECT @@SESSION.gtid_domain_id;
+@@SESSION.gtid_domain_id
+0
+SET GLOBAL gtid_domain_id= @old_domain;
+INSERT INTO t1 VALUES (101);
+SELECT * FROM t1 ORDER BY a;
+a
+1
+100
+101
+ROLLBACK;
+SELECT * FROM t1 ORDER BY a;
+a
+1
 *** Test requesting an explicit GTID position that conflicts with newer GTIDs of our own in the binlog. ***
 include/stop_slave.inc
 RESET MASTER;

mysql-test/suite/rpl/t/rpl_gtid_errorhandling.test

@@ -52,6 +52,23 @@ ALTER TABLE mysql.gtid_slave_pos ADD PRIMARY KEY (domain_id, sub_id);
 SELECT * FROM t1;
 
 
+--echo *** Test that setting @@gtid_domain_id or @@gtid_seq_no is not allowed inside a transaction. ***
+BEGIN;
+INSERT INTO t1 VALUES (100);
+--error ER_INSIDE_TRANSACTION_PREVENTS_SWITCH_GTID_DOMAIN_ID_SEQ_NO
+SET SESSION gtid_domain_id= 100;
+--error ER_INSIDE_TRANSACTION_PREVENTS_SWITCH_GTID_DOMAIN_ID_SEQ_NO
+SET SESSION gtid_seq_no= 100;
+SET @old_domain= @@GLOBAL.gtid_domain_id;
+SET GLOBAL gtid_domain_id= 100;
+SELECT @@SESSION.gtid_domain_id;
+SET GLOBAL gtid_domain_id= @old_domain;
+INSERT INTO t1 VALUES (101);
+SELECT * FROM t1 ORDER BY a;
+ROLLBACK;
+SELECT * FROM t1 ORDER BY a;
+
+
 --echo *** Test requesting an explicit GTID position that conflicts with newer GTIDs of our own in the binlog. ***
 --connection slave
 --source include/stop_slave.inc

sql/share/errmsg-utf8.txt

@@ -6551,3 +6551,7 @@ ER_GTID_START_FROM_BINLOG_HOLE
 	eng "The binlog on the master is missing the GTID %u-%u-%llu requested by the slave (even though both a prior and a subsequent sequence number does exist), and GTID strict mode is enabled"
 ER_SLAVE_UNEXPECTED_MASTER_SWITCH
 	eng "Unexpected GTID received from master after reconnect. This normally indicates that the master server was replaced without restarting the slave threads. %s"
+ER_INSIDE_TRANSACTION_PREVENTS_SWITCH_GTID_DOMAIN_ID_SEQ_NO
+        eng "Cannot modify @@session.gtid_domain_id or @@session.gtid_seq_no inside a transaction"
+ER_STORED_FUNCTION_PREVENTS_SWITCH_GTID_DOMAIN_ID_SEQ_NO
+        eng "Cannot modify @@session.gtid_domain_id or @@session.gtid_seq_no inside a stored function or trigger"

sql/sys_vars.cc

@@ -1203,6 +1203,21 @@ static Sys_var_ulong Sys_pseudo_thread_id(
        BLOCK_SIZE(1), NO_MUTEX_GUARD, IN_BINLOG,
        ON_CHECK(check_has_super));
 
+static bool
+check_gtid_domain_id(sys_var *self, THD *thd, set_var *var)
+{
+  if (check_has_super(self, thd, var))
+    return true;
+  if (var->type != OPT_GLOBAL &&
+      error_if_in_trans_or_substatement(thd,
+          ER_STORED_FUNCTION_PREVENTS_SWITCH_GTID_DOMAIN_ID_SEQ_NO,
+          ER_INSIDE_TRANSACTION_PREVENTS_SWITCH_GTID_DOMAIN_ID_SEQ_NO))
+    return true;
+
+  return false;
+}
+
+
 static Sys_var_uint Sys_gtid_domain_id(
        "gtid_domain_id",
        "Used with global transaction ID to identify logically independent "
@@ -1213,7 +1228,7 @@ static Sys_var_uint Sys_gtid_domain_id(
        SESSION_VAR(gtid_domain_id),
        CMD_LINE(REQUIRED_ARG), VALID_RANGE(0, UINT_MAX32), DEFAULT(0),
        BLOCK_SIZE(1), NO_MUTEX_GUARD, NOT_IN_BINLOG,
-       ON_CHECK(check_has_super));
+       ON_CHECK(check_gtid_domain_id));
 
 
 static bool check_gtid_seq_no(sys_var *self, THD *thd, set_var *var)
@@ -1223,6 +1238,11 @@ static bool check_gtid_seq_no(sys_var *self, THD *thd, set_var *var)
 
   if (check_has_super(self, thd, var))
     return true;
+  if (error_if_in_trans_or_substatement(thd,
+          ER_STORED_FUNCTION_PREVENTS_SWITCH_GTID_DOMAIN_ID_SEQ_NO,
+          ER_INSIDE_TRANSACTION_PREVENTS_SWITCH_GTID_DOMAIN_ID_SEQ_NO))
+    return true;
+
   domain_id= thd->variables.gtid_domain_id;
   server_id= thd->variables.server_id;
   seq_no= (uint64)var->value->val_uint();