Bug #37221: SET AUTOCOMMIT=1 does not commit binary log

When setting AUTOCOMMIT=1 after starting a transaction, the binary log
did not commit the outstanding transaction. The reason was that the binary
log commit function saw the values of the new settings, deciding that there
were nothing to commit.

Fixed the problem by moving the implicit commit to before the thread option
flags were changed, so that the binary log sees the old values of the flags
instead of the values they will take after the statement.

mysql-test/extra/binlog_tests/implicit.test

+# First part: outside a transaction
+RESET MASTER;
+eval $prepare;
+
+INSERT INTO t1 VALUES (1);
+source include/show_binlog_events.inc;
+eval $statement;
+source include/show_binlog_events.inc;
+if (`select '$cleanup' != ''`) {
+  eval $cleanup;
+}
+
+# Second part: inside a transaction
+RESET MASTER;
+eval $prepare;
+BEGIN;
+INSERT INTO t1 VALUES (2);
+source include/show_binlog_events.inc;
+eval $statement;
+source include/show_binlog_events.inc;
+INSERT INTO t1 VALUES (3);
+source include/show_binlog_events.inc;
+COMMIT;
+source include/show_binlog_events.inc;
+if (`select '$cleanup' != ''`) {
+  eval $cleanup;
+}
+

mysql-test/suite/binlog/t/binlog_implicit_commit.test

+# The purpose of this test is to test that setting autocommit does a
+# commit of outstanding transactions and nothing is left pending in
+# the transaction cache.
+
+source include/have_log_bin.inc;
+source include/have_innodb.inc;
+
+# We need a transactional engine, so let's use InnoDB
+CREATE TABLE t1 (id INT) ENGINE = InnoDB;
+
+# Testing SET AUTOCOMMIT
+SET BINLOG_FORMAT = STATEMENT;
+
+let $cleanup = COMMIT;
+
+let $prepare = SET AUTOCOMMIT = 0;
+let $statement = SET AUTOCOMMIT = 1;
+source extra/binlog_tests/implicit.test;
+
+let $prepare = SET AUTOCOMMIT = 1;
+let $statement = SET AUTOCOMMIT = 1;
+source extra/binlog_tests/implicit.test;
+
+let $prepare = SET AUTOCOMMIT = 0;
+let $statement = SET AUTOCOMMIT = 0;
+source extra/binlog_tests/implicit.test;
+
+let $prepare = SET AUTOCOMMIT = 1;
+let $statement = SET AUTOCOMMIT = 0;
+source extra/binlog_tests/implicit.test;
+
+SET BINLOG_FORMAT = ROW;
+let $prepare = SET AUTOCOMMIT = 0;
+let $statement = SET AUTOCOMMIT = 1;
+source extra/binlog_tests/implicit.test;
+
+let $prepare = SET AUTOCOMMIT = 1;
+let $statement = SET AUTOCOMMIT = 1;
+source extra/binlog_tests/implicit.test;
+
+let $prepare = SET AUTOCOMMIT = 0;
+let $statement = SET AUTOCOMMIT = 0;
+source extra/binlog_tests/implicit.test;
+
+let $prepare = SET AUTOCOMMIT = 1;
+let $statement = SET AUTOCOMMIT = 0;
+source extra/binlog_tests/implicit.test;
+
+RESET MASTER;
+SET AUTOCOMMIT = 0;
+INSERT INTO t1 VALUES (1);
+source include/show_binlog_events.inc;
+LOCK TABLES t1 WRITE;
+source include/show_binlog_events.inc;
+INSERT INTO t1 VALUES (2);
+source include/show_binlog_events.inc;
+UNLOCK TABLES;
+source include/show_binlog_events.inc;
+COMMIT;
+source include/show_binlog_events.inc;
+
+# Cleaning up
+DROP TABLE t1;

sql/set_var.cc

@@ -3054,6 +3054,15 @@ static bool set_option_autocommit(THD *thd, set_var *var)
 
   ulonglong org_options= thd->options;
 
+  /*
+    If we are setting AUTOCOMMIT=1 and it was not already 1, then we
+    need to commit any outstanding transactions.
+   */
+  if (var->save_result.ulong_value != 0 &&
+      (thd->options & OPTION_NOT_AUTOCOMMIT) &&
+      ha_commit(thd))
+    return 1;
+
   if (var->save_result.ulong_value != 0)
     thd->options&= ~((sys_var_thd_bit*) var->var)->bit_flag;
   else
@@ -3067,8 +3076,6 @@ static bool set_option_autocommit(THD *thd, set_var *var)
       thd->options&= ~(ulonglong) (OPTION_BEGIN | OPTION_KEEP_LOG);
       thd->transaction.all.modified_non_trans_table= FALSE;
       thd->server_status|= SERVER_STATUS_AUTOCOMMIT;
-      if (ha_commit(thd))
-	return 1;
     }
     else
     {