[Labs-l] Empty Cat query
Huji Lee
huji.huji at gmail.com
Fri Sep 23 16:02:14 UTC 2016
With two connections to the DB via Terminal, it is possible! Here is what I
got; it matches what you sent above too:
MariaDB [fawiki_p]> show processlist;
+---------+--------+-------------------+----------+---------+------+----------------------------+------------------------------------------------------------------------------------------------------+----------+
| Id | User | Host | db | Command | Time |
State |
Info
| Progress |
+---------+--------+-------------------+----------+---------+------+----------------------------+------------------------------------------------------------------------------------------------------+----------+
| 3556437 | s51403 | 10.68.23.58:53391 | fawiki_p | Query | 19 |
Queried about 5450000 rows | select page_title, count(ll_lang) from page
join category on page_title = cat_title left join catego | 0.000 |
| 3556865 | s51403 | 10.68.23.58:54083 | fawiki_p | Query | 0 |
init | show
processlist
| 0.000 |
+---------+--------+-------------------+----------+---------+------+----------------------------+------------------------------------------------------------------------------------------------------+----------+
2 rows in set (0.00 sec)
MariaDB [fawiki_p]> show explain for 3556437;
+------+-------------+---------------+--------+----------------------------------------+-----------------------------+---------+------------------------+--------+----------------------------------------------+
| id | select_type | table | type |
possible_keys | key |
key_len | ref | rows |
Extra |
+------+-------------+---------------+--------+----------------------------------------+-----------------------------+---------+------------------------+--------+----------------------------------------------+
| 1 | SIMPLE | page | ref |
name_title,page_redirect_namespace_len | page_redirect_namespace_len |
5 | const,const | 364177 | Using where; Using temporary;
Using filesort |
| 1 | SIMPLE | category | eq_ref |
cat_title | cat_title |
257 | fawiki.page.page_title | 1 | Using
index |
| 1 | SIMPLE | categorylinks | ref |
cl_timestamp,cl_sortkey | cl_timestamp |
257 | fawiki.page.page_title | 12 | Using where; Using
index |
| 1 | SIMPLE | templatelinks | ref |
tl_from,tl_namespace | tl_namespace |
4 | const | 390622 | Using where; Using
index |
| 1 | SIMPLE | langlinks | ref |
ll_from | ll_from |
4 | fawiki.page.page_id | 104911 | Using
index |
+------+-------------+---------------+--------+----------------------------------------+-----------------------------+---------+------------------------+--------+----------------------------------------------+
On Fri, Sep 23, 2016 at 11:58 AM, Huji Lee <huji.huji at gmail.com> wrote:
> Oh, I misread your comment.
>
> I doubt SHOW EXPLAIN would work via Quarry, so I am trying to get it to
> work via terminal access to Labs. I wonder though if it works for a query
> that fails to complete.
>
> On Fri, Sep 23, 2016 at 11:53 AM, Jaime Crespo <jcrespo at wikimedia.org>
> wrote:
>
>> Huji, note I suggested SHOW EXPLAIN, not EXPLAIN; it is a different
>> command, check the link I provided and report if that doesn't work for you.
>>
>> On Fri, Sep 23, 2016 at 5:31 PM, Huji Lee <huji.huji at gmail.com> wrote:
>>
>>> See https://quarry.wmflabs.org/query/12718 and the error message
>>> returned.
>>>
>>> EXPLAIN only works if you have access to the underlying tables. I only
>>> have access to the VIEWs built on top of actual wiki tables (for good
>>> reason, same applies to most of us) so I get an error when I try EXPLAIN.
>>>
>>> On Fri, Sep 23, 2016 at 11:24 AM, Jaime Crespo <jcrespo at wikimedia.org>
>>> wrote:
>>>
>>>> Explain (you should be able to run SHOW EXPLAIN on your own queries:
>>>> http://s.petrunia.net/blog/?p=89):
>>>>
>>>> EXPLAIN select page_title, count(ll_lang) from page join category on
>>>> page_title = cat_title left join categorylinks on page_title = cl_to left
>>>> join templatelinks on tl_from = page_id and tl_namespace = 10 and tl_title
>>>> in ( 'رده_خالی' , 'رده_بهتر', 'رده_ابهامزدایی', 'رده_ردیابیکردن' ) left
>>>> join langlinks on page_id = ll_from where page_namespace = 14 and
>>>> page_is_redirect = 0 and cl_to is null and tl_title is null group by
>>>> page_title order by 2, 1 limit 5000\G
>>>> *************************** 1. row ***************************
>>>> id: 1
>>>> select_type: SIMPLE
>>>> table: page
>>>> type: ref
>>>> possible_keys: name_title,page_redirect_namespace_len
>>>> key: page_redirect_namespace_len
>>>> key_len: 5
>>>> ref: const,const
>>>> rows: 364273
>>>> Extra: Using where; Using temporary; Using filesort
>>>> *************************** 2. row ***************************
>>>> id: 1
>>>> select_type: SIMPLE
>>>> table: category
>>>> type: eq_ref
>>>> possible_keys: cat_title
>>>> key: cat_title
>>>> key_len: 257
>>>> ref: fawiki.page.page_title
>>>> rows: 1
>>>> Extra: Using index
>>>> *************************** 3. row ***************************
>>>> id: 1
>>>> select_type: SIMPLE
>>>> table: categorylinks
>>>> type: ref
>>>> possible_keys: cl_timestamp,cl_sortkey
>>>> key: cl_timestamp
>>>> key_len: 257
>>>> ref: fawiki.page.page_title
>>>> rows: 12
>>>> Extra: Using where; Using index
>>>> *************************** 4. row ***************************
>>>> id: 1
>>>> select_type: SIMPLE
>>>> table: templatelinks
>>>> type: ref
>>>> possible_keys: tl_from,tl_namespace
>>>> key: tl_namespace
>>>> key_len: 4
>>>> ref: const
>>>> rows: 390610
>>>> Extra: Using where; Using index
>>>> *************************** 5. row ***************************
>>>> id: 1
>>>> select_type: SIMPLE
>>>> table: langlinks
>>>> type: ref
>>>> possible_keys: ll_from
>>>> key: ll_from
>>>> key_len: 4
>>>> ref: fawiki.page.page_id
>>>> rows: 104910
>>>> Extra: Using index
>>>>
>>>> On Fri, Sep 23, 2016 at 5:16 PM, Huji Lee <huji.huji at gmail.com> wrote:
>>>>
>>>>> Hi all,
>>>>>
>>>>> I have a query [1] which I run weekly to identify empty categories;
>>>>> those that don't have interwiki links and stay empty for a while are then
>>>>> deleted by a sysop.
>>>>>
>>>>> The query ran just fine every week until Sep 2nd. [2] Since then, the
>>>>> query times out and the page doesn't get updated.
>>>>>
>>>>> The query is no that complex (a SELECT with five JOINs) and used to
>>>>> finish in about 3-5 minutes. I don't have EXPLAIN access on Labs so I
>>>>> cannot tell what is slowing it down. Can someone kindly take a look and
>>>>> advise why this suddenly stopped working?
>>>>>
>>>>> Thanks,
>>>>>
>>>>> Huji
>>>>>
>>>>> [1] https://quarry.wmflabs.org/query/3760
>>>>> [2] https://fa.wikipedia.org/w/index.php?title=%D9%88%DB%8C%DA%A
>>>>> 9%DB%8C%E2%80%8C%D9%BE%D8%AF%DB%8C%D8%A7:%DA%AF%D8%B2%D8%A7%
>>>>> D8%B1%D8%B4_%D8%AF%DB%8C%D8%AA%D8%A7%D8%A8%DB%8C%D8%B3/%D8%B
>>>>> 1%D8%AF%D9%87%E2%80%8C%D9%87%D8%A7%DB%8C_%D8%AE%D8%A7%D9%84%
>>>>> DB%8C&action=history&uselang=en
>>>>>
>>>>> _______________________________________________
>>>>> Labs-l mailing list
>>>>> Labs-l at lists.wikimedia.org
>>>>> https://lists.wikimedia.org/mailman/listinfo/labs-l
>>>>>
>>>>>
>>>>
>>>>
>>>> --
>>>> Jaime Crespo
>>>> <http://wikimedia.org>
>>>>
>>>> _______________________________________________
>>>> Labs-l mailing list
>>>> Labs-l at lists.wikimedia.org
>>>> https://lists.wikimedia.org/mailman/listinfo/labs-l
>>>>
>>>>
>>>
>>> _______________________________________________
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>>>
>>>
>>
>>
>> --
>> Jaime Crespo
>> <http://wikimedia.org>
>>
>> _______________________________________________
>> Labs-l mailing list
>> Labs-l at lists.wikimedia.org
>> https://lists.wikimedia.org/mailman/listinfo/labs-l
>>
>>
>
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