Fix for bug #35732: read-only blocks SELECT statements in InnoDB

Problem: SELECTs prohibited for a transactional SE in autocommit mode
if read_only is set.

Fix: allow them.


mysql-test/r/read_only_innodb.result:
  Fix for bug #35732: read-only blocks SELECT statements in InnoDB
    - test result.
mysql-test/t/read_only_innodb.test:
  Fix for bug #35732: read-only blocks SELECT statements in InnoDB
    - test case.
sql/handler.cc:
  Fix for bug #35732: read-only blocks SELECT statements in InnoDB
    - in autocommit mode thd->transaction.all list is empty thus 
      is_real_trans set to TRUE for any SELECTs, so using it in the
      "read_only" check is insufficient.
      ha_check_and_coalesce_trx_read_only() changed to return number
      of engines with read-write changes. This value is used in the
      "read-only" check and checks for GLOBAL READ LOCK.
sql/lock.cc:
  Fix for bug #35732: read-only blocks SELECT statements in InnoDB
    - added assert(protect_against_global_read_lock) before decreasing,
      in order to catch (uint) 0 - 1 situation due to wrong 
      wait_if_global_read_lock()/start_waiting_global_read_lock() call
      sequence.

2 files changed, 72 insertions, 0 deletions

diff --git a/mysql-test/r/read_only_innodb.result b/mysql-test/r/read_only_innodb.result
index d028e3cc207..690de085bf9 100644
--- a/mysql-test/r/read_only_innodb.result
+++ b/mysql-test/r/read_only_innodb.result
@@ -16,3 +16,33 @@ ERROR HY000: The MySQL server is running with the --read-only option so it canno
 set global read_only=0;
 drop table table_11733 ;
 drop user test@localhost;
+GRANT CREATE, SELECT, DROP ON *.* TO test@localhost;
+CREATE TABLE t1(a INT) ENGINE=INNODB;
+INSERT INTO t1 VALUES (0), (1);
+SET GLOBAL read_only=1;
+SELECT * FROM t1;
+a
+0
+1
+BEGIN;
+SELECT * FROM t1;
+a
+0
+1
+COMMIT;
+SET GLOBAL read_only=0;
+FLUSH TABLES WITH READ LOCK;
+SELECT * FROM t1;
+a
+0
+1
+BEGIN;
+SELECT * FROM t1;
+a
+0
+1
+COMMIT;
+UNLOCK TABLES;
+DROP TABLE t1;
+DROP USER test@localhost;
+echo End of 5.1 tests 
diff --git a/mysql-test/t/read_only_innodb.test b/mysql-test/t/read_only_innodb.test
index 76d9748aa60..f8c25fdee1d 100644
--- a/mysql-test/t/read_only_innodb.test
+++ b/mysql-test/t/read_only_innodb.test
@@ -41,3 +41,45 @@ set global read_only=0;
 drop table table_11733 ;
 drop user test@localhost;
 
+disconnect con1;
+
+#
+# Bug #35732: read-only blocks SELECT statements in InnoDB
+#
+# Test 1: read only mode
+GRANT CREATE, SELECT, DROP ON *.* TO test@localhost;
+connect(con1, localhost, test, , test);
+
+connection default;
+CREATE TABLE t1(a INT) ENGINE=INNODB;
+INSERT INTO t1 VALUES (0), (1);
+SET GLOBAL read_only=1;
+
+connection con1;
+SELECT * FROM t1;
+BEGIN;
+SELECT * FROM t1;
+COMMIT;
+
+connection default;
+SET GLOBAL read_only=0;
+
+#
+# Test 2: global read lock
+#
+FLUSH TABLES WITH READ LOCK;
+
+connection con1;
+SELECT * FROM t1;
+BEGIN;
+SELECT * FROM t1;
+COMMIT;
+
+connection default;
+UNLOCK TABLES;
+DROP TABLE t1;
+DROP USER test@localhost;
+
+disconnect con1;
+
+--echo echo End of 5.1 tests