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Bug#44664: valgrind warning for COMMIT_AND_CHAIN and ROLLBACK_AND_CHAIN

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The problem is that the internal variable used to specify a
transaction with consistent read was being used outside the
processing context of a START TRANSACTION WITH CONSISTENT
SNAPSHOT statement. The practical consequence was that a
consistent snapshot specification could leak to unrelated
transactions on the same session.

The solution is to ensure a consistent snapshot clause is
only relied upon for the START TRANSACTION statement.

This is already fixed in a similar way on 6.0.

mysql-test/r/consistent_snapshot.result:
  Add test case result for Bug#44664
mysql-test/t/consistent_snapshot.test:
  Add test case for Bug#44664
sql/sql_parse.cc:
  The WITH CONSISTENT SNAPSHOT clause is only valid for the
  START TRANSACTION statement.
This commit is contained in:
Davi Arnaut 2009-05-11 20:54:00 -03:00
parent 9320c933be
commit d37aa50557
3 changed files with 48 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

19
mysql-test/r/consistent_snapshot.result
View File

@ -1,6 +1,9 @@
DROP TABLE IF EXISTS t1;
# Establish connection con1 (user=root)
# Establish connection con2 (user=root)
### Test 1:
### - While a consistent snapshot transaction is executed,
### no external inserts should be visible to the transaction.
# Switch to connection con1
CREATE TABLE t1 (a INT) ENGINE=innodb;
START TRANSACTION WITH CONSISTENT SNAPSHOT;
@ -10,6 +13,9 @@ INSERT INTO t1 VALUES(1);
SELECT * FROM t1;
a
COMMIT;
### Test 2:
### - For any non-consistent snapshot transaction, external
### committed inserts should be visible to the transaction.
DELETE FROM t1;
START TRANSACTION;
# Switch to connection con2
@ -19,5 +25,18 @@ SELECT * FROM t1;
a
1
COMMIT;
### Test 3:
### - Bug#44664: valgrind warning for COMMIT_AND_CHAIN and ROLLBACK_AND_CHAIN
### Chaining a transaction does not retain consistency level.
START TRANSACTION WITH CONSISTENT SNAPSHOT;
DELETE FROM t1;
COMMIT WORK AND CHAIN;
# Switch to connection con2
INSERT INTO t1 VALUES(1);
# Switch to connection con1
SELECT * FROM t1;
a
1
COMMIT;
# Switch to connection default + close connections con1 and con2
DROP TABLE t1;

30
mysql-test/t/consistent_snapshot.test
View File

@ -12,9 +12,9 @@ connect (con1,localhost,root,,);
--echo # Establish connection con2 (user=root)
connect (con2,localhost,root,,);
### Test 1:
### - While a consistent snapshot transaction is executed,
### no external inserts should be visible to the transaction.
--echo ### Test 1:
--echo ### - While a consistent snapshot transaction is executed,
--echo ### no external inserts should be visible to the transaction.
--echo # Switch to connection con1
connection con1;
@ -31,9 +31,9 @@ SELECT * FROM t1; # if consistent snapshot was set as expected, we
# should see nothing.
COMMIT;
### Test 2:
### - For any non-consistent snapshot transaction, external
### committed inserts should be visible to the transaction.
--echo ### Test 2:
--echo ### - For any non-consistent snapshot transaction, external
--echo ### committed inserts should be visible to the transaction.
DELETE FROM t1;
START TRANSACTION; # Now we omit WITH CONSISTENT SNAPSHOT
@ -48,6 +48,24 @@ SELECT * FROM t1; # if consistent snapshot was not set, as expected, we
# should see 1.
COMMIT;
--echo ### Test 3:
--echo ### - Bug#44664: valgrind warning for COMMIT_AND_CHAIN and ROLLBACK_AND_CHAIN
--echo ### Chaining a transaction does not retain consistency level.
START TRANSACTION WITH CONSISTENT SNAPSHOT;
DELETE FROM t1;
COMMIT WORK AND CHAIN;
--echo # Switch to connection con2
connection con2;
INSERT INTO t1 VALUES(1);
--echo # Switch to connection con1
connection con1;
SELECT * FROM t1; # if consistent snapshot was not set, as expected, we
# should see 1.
COMMIT;
--echo # Switch to connection default + close connections con1 and con2
connection default;
disconnect con1;

7
sql/sql_parse.cc
View File

@ -198,8 +198,6 @@ bool begin_trans(THD *thd)
LEX *lex= thd->lex;
thd->options|= OPTION_BEGIN;
thd->server_status|= SERVER_STATUS_IN_TRANS;
if (lex->start_transaction_opt & MYSQL_START_TRANS_OPT_WITH_CONS_SNAPSHOT)
error= ha_start_consistent_snapshot(thd);
}
return error;
}
@ -4027,6 +4025,11 @@ end_with_restore_list:
}
if (begin_trans(thd))
goto error;
if (lex->start_transaction_opt & MYSQL_START_TRANS_OPT_WITH_CONS_SNAPSHOT)
{
if (ha_start_consistent_snapshot(thd))
goto error;
}
my_ok(thd);
break;
case SQLCOM_COMMIT: