orry many mails " The server is free to choose any value from each group, so unless they are the same, the values chosen are indeterminate. " 2014-05-23 15:32 GMT-03:00 Roberto Spadim :

http://dev.mysql.com/doc/refman/5.6/en/group-by-extensions.html

here, but must check if mariadb have something like it

2014-05-23 15:21 GMT-03:00 Roberto Spadim :

maybe you should use something like MIN() MAX(), since you are using a

...

GROUP BY i don't know if this is well documented but i think it's

2014-05-23 15:18 GMT-03:00 Charles Cazabon < charlesc-web-register-launchpad.net@pyropus.ca>:

Greetings,

...

I recently upgraded the db server behind an application from MySQL 5.1.73 (as shipped in Ubuntu 10.04 "Lucid") to MariaDB 10.0.11 (from the MariaDB repo).

A colleague of mine found an inconsistency between the results produced by the two servers for a given query. What we don't know is, is this a bug (I gather Maria is aiming at 100% compatibility), or is this somehow due to the query relying on unspecified behaviour (that the two db servers are therefore free to optimize differently)?

The query is:

SELECT t1.id, t2.album_id FROM t1 LEFT OUTER JOIN t2 ON t1.data_id = t2.id AND t1.event_type IN (1002, 1001, 1000) WHERE t1.event_type IN (1000, 1001, 1002, 1200, 1201, 1202, 1203) GROUP BY t1.id ORDER BY t1.id DESC LIMIT 0, 20;

The MariaDB result looks like this:

+-----+----------+ | id | album_id | +-----+----------+ | 623 | NULL | | 622 | NULL | | 621 | NULL | | 620 | NULL | | 619 | NULL | | 618 | NULL | | 617 | NULL | | 616 | NULL | | 615 | NULL | | 614 | NULL | | 613 | NULL | | 612 | 194 | | 611 | NULL | | 610 | NULL | | 609 | NULL | | 608 | 193 | | 607 | NULL | | 606 | NULL | | 605 | NULL | | 604 | NULL | +-----+----------+

And the Oracle MySQL result looks like this:

+-----+----------+ | id | album_id | +-----+----------+ | 623 | NULL | | 622 | NULL | | 621 | NULL | | 620 | NULL | | 619 | NULL | | 618 | NULL | | 617 | NULL | | 616 | 196 |<-- different | 615 | NULL | | 614 | NULL | | 613 | NULL | | 612 | 194 | | 611 | 194 |<-- different | 610 | NULL | | 609 | NULL | | 608 | 193 | | 607 | 193 |<-- different | 606 | NULL | | 605 | NULL | | 604 | NULL | +-----+----------+

My colleague pointed out that if you EXPLAIN the queries, you can see that the two databases are interpreting the query differently -- see the "Extra" column. I can't paste the explain output here without using very long lines, so I've pastebinned it: http://pastebin.com/n2sbH0kY

My colleague has made the data from these tables available here: https://dl.dropboxusercontent.com/u/7755033/fatdrop/test_case_data.sql

We've found workarounds for this, but we're really wondering if we've found a problem (either in MariaDB-MySQL consistency, or in the query, or ... ?).

Any assistance appreciated.

Charles -- ------------------------------------------------------------------ Charles Cazabon Software, consulting, and services available at http://pyropus.ca/ ------------------------------------------------------------------

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-- Roberto Spadim SPAEmpresarial Eng. Automação e Controle

-- Roberto Spadim SPAEmpresarial Eng. Automação e Controle

-- Roberto Spadim SPAEmpresarial Eng. Automação e Controle

Roberto, Federico, While I agree with your comments regarding use of ONLY_FULL_GROUP_BY, the specific case has primary keys defined on (id), on both tables. So, the GROUP BY t1.id has (or should have) no effect as every group will have exactly one row and the results should be the deterministic. I think Pavel is correct and this is a bug. Pantelis On Fri, May 23, 2014 at 8:16 PM, Federico Razzoli wrote:

Hi! From MySQL documentation: http://dev.mysql.com/doc/refman/5.6/en/group-by-extensions.html

"MySQL extends the use of GROUP BY so that the select list can refer to nonaggregated columns not named in the GROUP BY clause. (...) However, this is useful primarily when all values in each nonaggregated column not named in the GROUP BY are the same for each group. The server is free to choose any value from each group, so unless they are the same, the values chosen are indeterminate."

This is the reason why I think that the ONLY_FULL_GROUP_BY sql_mode flag should always be on.

In your specific case, I note that album_id is not in GROUP BY and is not passed to any aggregating function (such as MAX()).

Regards Federico

-------------------------------------------- El vie, 23/5/14, Charles Cazabon < charlesc-web-register-launchpad.net@pyropus.ca> escribió:

Asunto: [Maria-discuss] query result inconsistency between MariaDB 10.0.x and Oracle MySQL 5.1.x Para: "MariaDB discuss" Fecha: viernes, 23 de mayo, 2014 20:18

Greetings,

I recently upgraded the db server behind an application from MySQL 5.1.73 (as shipped in Ubuntu 10.04 "Lucid") to MariaDB 10.0.11 (from the MariaDB repo).

A colleague of mine found an inconsistency between the results produced by the two servers for a given query. What we don't know is, is this a bug (I gather Maria is aiming at 100% compatibility), or is this somehow due to the query relying on unspecified behaviour (that the two db servers are therefore free to optimize differently)?

The query is:

SELECT t1.id, t2.album_id FROM t1 LEFT OUTER JOIN t2 ON t1.data_id = t2.id AND t1.event_type IN (1002, 1001, 1000) WHERE t1.event_type IN (1000, 1001, 1002, 1200, 1201, 1202, 1203) GROUP BY t1.id ORDER BY t1.id DESC LIMIT 0, 20;

The MariaDB result looks like this:

+-----+----------+ | id | album_id | +-----+----------+ | 623 | NULL | | 622 | NULL | | 621 | NULL | | 620 | NULL | | 619 | NULL | | 618 | NULL | | 617 | NULL | | 616 | NULL | | 615 | NULL | | 614 | NULL | | 613 | NULL | | 612 | 194 | | 611 | NULL | | 610 | NULL | | 609 | NULL | | 608 | 193 | | 607 | NULL | | 606 | NULL | | 605 | NULL | | 604 | NULL | +-----+----------+

And the Oracle MySQL result looks like this:

+-----+----------+ | id | album_id | +-----+----------+ | 623 | NULL | | 622 | NULL | | 621 | NULL | | 620 | NULL | | 619 | NULL | | 618 | NULL | | 617 | NULL | | 616 | 196 |<-- different | 615 | NULL | | 614 | NULL | | 613 | NULL | | 612 | 194 | | 611 | 194 |<-- different | 610 | NULL | | 609 | NULL | | 608 | 193 | | 607 | 193 |<-- different | 606 | NULL | | 605 | NULL | | 604 | NULL | +-----+----------+

My colleague pointed out that if you EXPLAIN the queries, you can see that the two databases are interpreting the query differently -- see the "Extra" column. I can't paste the explain output here without using very long lines, so I've pastebinned it: http://pastebin.com/n2sbH0kY

My colleague has made the data from these tables available here: https://dl.dropboxusercontent.com/u/7755033/fatdrop/test_case_data.sql

We've found workarounds for this, but we're really wondering if we've found a problem (either in MariaDB-MySQL consistency, or in the query, or ... ?).

Any assistance appreciated.

Charles -- ------------------------------------------------------------------ Charles Cazabon Software, consulting, and services available at http://pyropus.ca/ ------------------------------------------------------------------

_______________________________________________ Mailing list: https://launchpad.net/~maria-discuss Post to : maria-discuss@lists.launchpad.net Unsubscribe : https://launchpad.net/~maria-discuss More help : https://help.launchpad.net/ListHelp

_______________________________________________ Mailing list: https://launchpad.net/~maria-discuss Post to : maria-discuss@lists.launchpad.net Unsubscribe : https://launchpad.net/~maria-discuss More help : https://help.launchpad.net/ListHelp

Pantelis, It is a left join and the ON doesn't include t1.id, so without GROUP BY, the id values are repeated. In fact, I get completely different results: MariaDB [test]> SELECT t1.id, t2.album_id -> FROM t1 -> LEFT OUTER JOIN t2 -> ON t1.data_id = t2.id -> AND t1.event_type IN (1002, 1001, 1000) -> WHERE -> t1.event_type IN (1000, 1001, 1002, 1200, 1201, 1202, 1203) -> GROUP BY t1.id LIMIT 0, 20; +----+----------+ | id | album_id | +----+----------+ | 1 | NULL | | 2 | NULL | | 3 | 1 | | 4 | 1 | | 5 | NULL | | 6 | NULL | | 7 | NULL | | 8 | 2 | | 9 | 2 | | 10 | NULL | | 11 | NULL | | 12 | NULL | | 13 | 3 | | 14 | NULL | | 15 | NULL | | 16 | NULL | | 17 | 4 | | 18 | NULL | | 19 | NULL | | 20 | NULL | +----+----------+ 20 rows in set (0.00 sec) I'm not saying it is not a bug - I don't have an opinion about this. I'm just suggesting to drop the GROUP BY from this query. Regards Federico -------------------------------------------- El vie, 23/5/14, Pantelis Theodosiou escribió: Asunto: Re: [Maria-discuss] query result inconsistency between MariaDB 10.0.x and Oracle MySQL 5.1.x Para: "MariaDB discuss" Fecha: viernes, 23 de mayo, 2014 21:50 Roberto, Federico, While I agree with your comments regarding use of ONLY_FULL_GROUP_BY, the specific case has primary keys defined on (id), on both tables. So, the GROUP BY t1.id has (or should have) no effect as every group will have exactly one row and the results should be the deterministic. I think Pavel is correct and this is a bug. Pantelis On Fri, May 23, 2014 at 8:16 PM, Federico Razzoli wrote: Hi! From MySQL documentation: http://dev.mysql.com/doc/refman/5.6/en/group-by-extensions.html "MySQL extends the use of GROUP BY so that the select list can refer to nonaggregated columns not named in the GROUP BY clause. (...) However, this is useful primarily when all values in each nonaggregated column not named in the GROUP BY are the same for each group. The server is free to choose any value from each group, so unless they are the same, the values chosen are indeterminate." This is the reason why I think that the ONLY_FULL_GROUP_BY sql_mode flag should always be on. In your specific case, I note that album_id is not in GROUP BY and is not passed to any aggregating function (such as MAX()). Regards Federico -------------------------------------------- El vie, 23/5/14, Charles Cazabon escribió:  Asunto: [Maria-discuss] query result inconsistency between MariaDB 10.0.x and Oracle MySQL 5.1.x  Para: "MariaDB discuss"  Fecha: viernes, 23 de mayo, 2014 20:18  Greetings,  I recently upgraded the db server behind an application from  MySQL 5.1.73 (as  shipped in Ubuntu 10.04 "Lucid") to MariaDB 10.0.11 (from  the MariaDB repo).  A colleague of mine found an inconsistency between the  results produced by the  two servers for a given query.  What we don't know is,  is this a bug (I gather  Maria is aiming at 100% compatibility), or is this somehow  due to the query  relying on unspecified behaviour (that the two db servers  are therefore free  to optimize differently)?  The query is:    SELECT t1.id, t2.album_id    FROM t1      LEFT OUTER JOIN t2        ON t1.data_id = t2.id        AND t1.event_type IN (1002, 1001,  1000)    WHERE      t1.event_type IN (1000, 1001, 1002, 1200,  1201, 1202, 1203)    GROUP BY t1.id    ORDER BY t1.id DESC    LIMIT 0, 20;  The MariaDB result looks like this:    +-----+----------+    | id  | album_id |    +-----+----------+    | 623 |     NULL |    | 622 |     NULL |    | 621 |     NULL |    | 620 |     NULL |    | 619 |     NULL |    | 618 |     NULL |    | 617 |     NULL |    | 616 |     NULL |    | 615 |     NULL |    | 614 |     NULL |    | 613 |     NULL |    | 612 |      194 |    | 611 |     NULL |    | 610 |     NULL |    | 609 |     NULL |    | 608 |      193 |    | 607 |     NULL |    | 606 |     NULL |    | 605 |     NULL |    | 604 |     NULL |    +-----+----------+  And the Oracle MySQL result looks like this:    +-----+----------+    | id  | album_id |    +-----+----------+    | 623 |     NULL |    | 622 |     NULL |    | 621 |     NULL |    | 620 |     NULL |    | 619 |     NULL |    | 618 |     NULL |    | 617 |     NULL |    | 616 |      196 |<-- different    | 615 |     NULL |    | 614 |     NULL |    | 613 |     NULL |    | 612 |      194 |    | 611 |      194 |<-- different    | 610 |     NULL |    | 609 |     NULL |    | 608 |      193 |    | 607 |      193 |<-- different    | 606 |     NULL |    | 605 |     NULL |    | 604 |     NULL |    +-----+----------+  My colleague pointed out that if you EXPLAIN the queries,  you can see that the  two databases are interpreting the query differently -- see  the "Extra"  column.  I can't paste the explain output here without  using very long lines,  so I've pastebinned it:  http://pastebin.com/n2sbH0kY  My colleague has made the data from these tables available  here:  https://dl.dropboxusercontent.com/u/7755033/fatdrop/test_case_data.sql  We've found workarounds for this, but we're really wondering  if we've found a  problem (either in MariaDB-MySQL consistency, or in the  query, or ... ?).  Any assistance appreciated.  Charles  --  ------------------------------------------------------------------  Charles Cazabon         Software, consulting, and services available at http://pyropus.ca/  ------------------------------------------------------------------  _______________________________________________  Mailing list: https://launchpad.net/~maria-discuss  Post to     : maria-discuss@lists.launchpad.net  Unsubscribe : https://launchpad.net/~maria-discuss  More help   : https://help.launchpad.net/ListHelp _______________________________________________ Mailing list: https://launchpad.net/~maria-discuss Post to     : maria-discuss@lists.launchpad.net Unsubscribe : https://launchpad.net/~maria-discuss More help   : https://help.launchpad.net/ListHelp -----Adjunto en línea a continuación----- _______________________________________________ Mailing list: https://launchpad.net/~maria-discuss Post to     : maria-discuss@lists.launchpad.net Unsubscribe : https://launchpad.net/~maria-discuss More help   : https://help.launchpad.net/ListHelp