bzr commit into mysql-5.1-bugteam branch (davi:2880) Bug#44664

[Davi Arnaut]

# At a local mysql-5.1-bugteam repository of davi

 2880 Davi Arnaut	2009-05-11
      Bug#44664: valgrind warning for COMMIT_AND_CHAIN and ROLLBACK_AND_CHAIN
      
      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.

    modified:
      mysql-test/r/consistent_snapshot.result
      mysql-test/t/consistent_snapshot.test
      sql/sql_parse.cc
=== modified file 'mysql-test/r/consistent_snapshot.result'
--- a/mysql-test/r/consistent_snapshot.result	2009-03-03 20:34:18 +0000
+++ b/mysql-test/r/consistent_snapshot.result	2009-05-11 23:54:00 +0000
@@ -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;

=== modified file 'mysql-test/t/consistent_snapshot.test'
--- a/mysql-test/t/consistent_snapshot.test	2009-03-03 20:34:18 +0000
+++ b/mysql-test/t/consistent_snapshot.test	2009-05-11 23:54:00 +0000
@@ -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 snapsh
 # 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 snapsh
 # 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;

=== modified file 'sql/sql_parse.cc'
--- a/sql/sql_parse.cc	2009-04-09 11:30:44 +0000
+++ b/sql/sql_parse.cc	2009-05-11 23:54:00 +0000
@@ -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:


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