MySQL Commited data not seen to select query

Context: The framework used is Spring and all queries are run with JdbcTemplate. Mysql Server version is 5.6.19. The table is an InnoDB table and defaults like auto commit and isolation level repeatable-read is set.

Problem: An Insert happens inside a transaction and a select which reads the same data inserted does not see the data. The select runs after the insert and after the insert transaction has commited.

I've enabled bin log as well as general log in mysql. Relevant logs below

bin-log:

SET TIMESTAMP=1438265764/*!*/;
BEGIN
/*!*/;
# at 249935389
#150730 14:16:04 server id 1  end_log_pos 249935606 CRC32 0xa6aca292    Query   thread_id=40    exec_time=0     error_code=0
SET TIMESTAMP=1438265764/*!*/;
insert into user_geo_loc_latest(user_id, lat, lng) values(x,y,z) on duplicate key update lat=y, lng=z
/*!*/;
# at 249935606
#150730 14:16:06 server id 1  end_log_pos 249936255 CRC32 0x2a52c734    Query   thread_id=40    exec_time=0     error_code=0
SET TIMESTAMP=1438265766/*!*/;
INSERT INTO table(txnid) VALUES ('885851438265675046')
/*!*/;
# at 249936255
#150730 14:16:06 server id 1  end_log_pos 249936514 CRC32 0x6cd85eb5    Query   thread_id=40    exec_time=0     error_code=0
SET TIMESTAMP=1438265766/*!*/;
INSERT INTO table2(x) VALUES (y)
/*!*/;
# at 249936514
#150730 14:16:06 server id 1  end_log_pos 249936545 CRC32 0xceb9ec56    Xid = 9406873
COMMIT/*!*/;

Query Log

```
150730 14:16:04 40 Query ...
....
40 Query select count(*) from table where txnid = '885851438265675046'
40 Query select @@session.tx_read_only
40 Query INSERT INTO table(txnid) VALUES ('885851438265675046')
40 Query select @@session.tx_read_only
40 Query INSERT INTO table2(x) values(y)
40 Query commit
....
150730 14:16:07 36 Query select pp.*, b.create_date from table pp left join bill b on pp.bill_id = b.bill_id where pp.txnid = '8858514

I try to make an hypothesis about the second question:


Given the commit happens before the select (commit is at 14:16:06 and
select is at 14:16:07) how is it that the select does not return the
row inserted by the transaction?

Transactions are managed by Spring. So it would be possible that before running the select spring has raised a start transaction or it has already used the connection for running an another query.

I start a first session where I simulate an insert into a table t:

session1> create table t (i int auto_increment primary key);
Query OK, 0 rows affected (0,32 sec)

session1> insert into t values();
Query OK, 1 row affected (0,00 sec)

session1> select * from t;
+---+
| i |
+---+
| 1 |
+---+
1 row in set (0,00 sec)

session1> start transaction;
Query OK, 0 rows affected (0,00 sec)

session1> insert into t values();
Query OK, 1 row affected (0,00 sec)

I create a new session, session2, where autocommit is set to 0. Into this new session, a transaction is implicitly started when running a select.

session2> set autocommit = 0;
Query OK, 0 rows affected (0,00 sec)

session2> select * from t;  -- this starts a transaction
+---+
| i |
+---+
| 1 |
+---+
1 rows in set (0,00 sec)

Move to session1 to commit the insert.

session1> commit;

Now move again to session2:

session2> select * from t;
+---+
| i |
+---+
| 1 |
+---+
1 row in set (0,00 sec)

Session2 cannot see the row just inserted. If a commit is raised in session2 we can see new row inserted in session1

session2> commit
1 row in set (0,00 sec)

session2> select * from t;
+---+
| i |
+---+
| 1 |
| 2 |
+---+
2 rows in set (0,00 sec)

The general log looks like :

150804 14:04:10     2 Query select * from t

150804 14:04:30     1 Query start transaction
150804 14:04:39     1 Query insert into t values ()
150804 14:04:44     1 Query commit
150804 14:04:51     2 Query select * from t

150804 14:05:07     2 Query commit
150804 14:05:10     2 Query select * from t

The first row is related to session 2. It is when session 2 opens the transaction.

I don't know if this is what happen in your case. You could check in your general log if the connection_id 36 was used for other queries. Let we know.

StackExchange Database Administrators Q#108544, answer score: 3