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Re: Index suggestion needed for performance improvement
Posted by: Ronald Brown
Date: October 04, 2015 09:18PM

> How much RAM do you have? What is the value of
> innodb_buffer_pool_size? That setting should
> typically be 70% of RAM.

i have 32 GB RAM , its a dedicated server acts as web-server and mysql server.
current
innodb_buffer_pool_size = 15G


> Did the EXPLAIN change? I suspect is is very
> similar. If it is different, I would be excited
> to see it.

explain changed key from e_c_d_v(enabled_category_upload_datverified) to e_s_d (enabled_seeders_upload_date)

mysql> explain SELECT content.title,content.og_name,content.record_num,content.category,content.upload_date,content.hash,content.comments_count,content.verified,content.uploader,content.size,content.seeders,content.leechers FROM content WHERE enabled = 1 AND category IN (800,801,802,803,804,805,806,807,808,809,810,811,812,813,814,815,816,817,818,819,820) ORDER BY seeders DESC , upload_date DESC LIMIT 0,25\G
*************************** 1. row ***************************
id: 1
select_type: SIMPLE
table: content
type: range
possible_keys: e_c_d_v,e_d_v,e_c_v,e_v,e_u,e_s_d
key: e_s_d
key_len: 1
ref: NULL
rows: 3398901
Extra: Using index condition; Using where
1 row in set (0.00 sec)



> Here is a technique that _might_ speed it up
> _some_:
>
>
>     SELECT 
> content.title,content.og_name,content.record_num,c
> ontent.category,
>            
> content.upload_date,content.hash,content.comments_
> count,
>            
> content.verified,content.uploader,content.size,con
> tent.seeders,
>             content.leechers
>         FROM  content
>         JOIN 
>           ( SELECT  record_num
>                 FROM  content
>                 WHERE  enabled = 1
>                   AND  category IN
> (800,801,802,803,804,805,806,807,808,809,
>                                    
> 810,811,812,813,814,815,816,817,818,819,820)
>                 ORDER BY  seeders DESC ,
> upload_date DESC
>                 LIMIT  0,25
>           ) x ON content.record_num =
> x.record_num; 
> 
> # together with this "covering" index for the
> subquery:
> INDEX(enabled, category, seeders, upload_date,
> record_num)
>
>
> Why it _might_ help:
> 1. The subquery will rummage through 1525431
> _narrow_ rows in the _covering_ index.
> 2. It will create a narrow tmp table for sorting
> and extracting 25 record_nums.
> 3. The outer SELECT will look up only the 25
> records.
>
> Caveat: You probably need ORDER BY seeders DESC
> , upload_date DESC at the end to get the rows in
> the right order. But this is a very minor
> filesort (25 rows, versus 1525431).
>
> The principles behind this 'trick' are:
> 1. "If FROM ( SELECT... ) will significantly
> decrease the number of rows looked at, the overall
> query may run faster."
> 2. "A covering index is faster."
>
> The caveat comes in that the added complexity
> costs something.


This looks great.



> Another technique that _might_ help. Or it might
> make things worse:
> INDEX(enabled, seeders, upload_date)
> This would be beneficial only if those categories
> happened to be near the end of the seeders.

this index is what i created , and then queres are fast.

Thanks

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Re: Index suggestion needed for performance improvement
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October 04, 2015 09:18PM


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