[Labs-l] Empty Cat query

Fri Sep 23 15:53:14 UTC 2016

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%B1%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>
>>
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>>
>
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-- 
Jaime Crespo
<http://wikimedia.org>
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