Question

MySQL / PHP select data faster

Asked by: us-pata

Hi.

I have a database with about 200k entries, and i try to show 20 next entries from entrynum ie. 84800.
This takes 4-8 seconds to execute, wich is way to long for å web-site.

Is there any way to execute this faster?
See the code field for the code i use.

mysql>  SELECT *
    -> FROM `images`
    -> WHERE chan = 'b'
    -> AND `reported`
    -> IN (
    -> '0', '1'
    -> )
    -> ORDER BY `id` ASC
    -> LIMIT 84800 , 20;
+--------+------+-------------------+----------------------------------+----------+-------+--------+----------+
| id     | chan | image             | md5                              | filesize | width | height | reported |
+--------+------+-------------------+----------------------------------+----------+-------+--------+----------+
| 116191 | b    | 1239642027572.jpg | 29cf26da75477b17dde7f44122c41c3b | 234525   | 881   | 1236   |        0 |
| 116192 | b    | 1239642039503.jpg | cdc0e5f8351c7b190f27b5452da40e29 | 30215    | 600   | 540    |        0 |
| 116193 | b    | 1239642042452.jpg | 5f4123fdf1aae8a5e26876761f20c17c | 160723   | 407   | 405    |        0 |
| 116194 | b    | 1239642044911.jpg | a65944cf224022426e7c959e5017bd83 | 86380    | 313   | 500    |        0 |
| 116195 | b    | 1239642045388.jpg | a9f32fa77d059d515c53c151a535f49f | 40498    | 640   | 342    |        0 |
| 116196 | b    | 1239642045716.jpg | 600f427fa525222538889a843edb45b1 | 65437    | 480   | 640    |        0 |
| 116197 | b    | 1239642047695.jpg | be4396ca231a3cd363483e27c8911464 | 162712   | 435   | 625    |        0 |
| 116198 | b    | 1239642050263.png | 51bedfb85f01b34f8338f29492800cc4 | 49279    | 901   | 538    |        0 |
| 116199 | b    | 1239642063400.jpg | 3815c2c4929a2b5fd0ea85a0b50c2b19 | 68896    | 469   | 297    |        0 |
| 116200 | b    | 1239642065678.jpg | 1fcd8f583ea7080c18ddef9dc0e3bdc8 | 152658   | 612   | 816    |        0 |
| 116201 | b    | 1239642067773.jpg | afb15e7adbf9a8cc7af801d311fefac4 | 27547    | 450   | 287    |        0 |
| 116202 | b    | 1239642071811.jpg | 42ac9aabd18996eeeca790a1f6f3a460 | 201878   | 834   | 1200   |        0 |
| 116203 | b    | 1239642076646.jpg | 3d5741c33476be17b1856a4619d26166 | 33359    | 492   | 370    |        0 |
| 116204 | b    | 1239642083927.jpg | 05f26039eb45647842937ff2e3dd48ec | 580083   | 1920  | 2576   |        0 |
| 116205 | b    | 1239642095095.jpg | 6978f1dd9812ceb682bc3e1a93dce724 | 22370    | 600   | 449    |        0 |
| 116206 | b    | 1239642105383.jpg | 0f67bb8adb74573c26b5d88a458572f1 | 236253   | 834   | 1200   |        0 |
| 116207 | b    | 1239642109318.jpg | 0737fc2429e6819ca2844d642933b82e | 90907    | 500   | 346    |        0 |
| 116208 | b    | 1239642112126.jpg | da391b6c8b68516dea67685755ebcfe9 | 64688    | 600   | 450    |        0 |
| 116209 | b    | 1239642113695.jpg | 79f692bdf914945e31d64bd97dbc169f | 186740   | 640   | 480    |        0 |
| 116210 | b    | 1239642118165.jpg | 52f2df0e7f89ce55b35c95ee2916d59d | 878492   | 2280  | 1600   |        0 |
+--------+------+-------------------+----------------------------------+----------+-------+--------+----------+
20 rows in set (6.65 sec)

                                  
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Asked On
2009-09-16 at 08:21:04ID24736622
Tags

php

,

mysql

,

sql

,

select

Topics

Databases Miscellaneous

,

PHP and Databases

,

PHP Scripting Language

Participating Experts
3
Points
250
Comments
10

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Answers

 

by: alain34Posted on 2009-09-16 at 08:41:22ID: 25346834

Hello us-pata,

Could you tell use if you have an index on any columns?

Regards,

alain34

 

by: us-pataPosted on 2009-09-16 at 08:48:48ID: 25346933

the id field is a primary index at 192420 right now

 

by: wuff1ukPosted on 2009-09-16 at 09:05:03ID: 25347132

set an index on chan and on reported.

 

by: TheWebMonsterPosted on 2009-09-16 at 09:29:11ID: 25347410

instead of selecting everything, select only the fields you will be using.

making other fields indexed helps. (should not have more then 3 indexed fields in a table)

If your "reported" field is an ENUM type set to '0','1' there is no point including it into your statement, because you are not filtering on it.

SELECT `image`,`md5`,`width`,`height` FROM `images` WHERE `chan` = 'b' ORDER BY `id` ASC LIMIT 84800 , 20;
                                              
1:

Select allOpen in new window

 

by: us-pataPosted on 2009-09-16 at 09:44:05ID: 25347552

Hi again.

I added an index to chan and reported and run the sql line specefied bby TheWebMonster.
The query took 14.9892 seconds to run now. witch is twice as long as "normal".

The intention of reported is that 0 = not reported, 1 = checked (OK), 2 or higher = needs check

 

by: wuff1ukPosted on 2009-09-16 at 10:17:23ID: 25347837

what's the output of explain ?

explain SELECT `image`,`md5`,`width`,`height` FROM `images` WHERE `chan` = 'b' ORDER BY `id` ASC LIMIT 84800 , 20;

                                              
1:

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by: us-pataPosted on 2009-09-16 at 10:35:57ID: 25348008

mysql> explain SELECT `image`,`md5`,`width`,`height` FROM `images` WHERE `chan` = 'b' ORDER BY `id` ASC LIMIT 84800 , 20;
+----+-------------+--------+------+---------------+------+---------+-------+--------+-----------------------------+
| id | select_type | table  | type | possible_keys | key  | key_len | ref   | rows   | Extra                       |
+----+-------------+--------+------+---------------+------+---------+-------+--------+-----------------------------+
|  1 | SIMPLE      | images | ref  | chan          | chan | 3       | const | 138873 | Using where; Using filesort |
+----+-------------+--------+------+---------------+------+---------+-------+--------+-----------------------------+
1 row in set (0.00 sec)
                                              
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by: wuff1ukPosted on 2009-09-16 at 11:02:57ID: 25348291

How does the query time improve if you don't sort the result?

 

by: us-pataPosted on 2009-09-16 at 13:53:18ID: 25350001

How dows this effect my result?

mysql> SELECT `image` , `md5` , `width` , `height`
    -> FROM `images`
    -> WHERE `chan` = 'b'
    -> LIMIT 84800 , 20;
+-------------------+----------------------------------+-------+--------+
| image             | md5                              | width | height |
+-------------------+----------------------------------+-------+--------+
| 1239642025933.jpg | 26c684939af9ee9e871640c0680baaa6 | 130   | 130    |
| 1239642027572.jpg | 29cf26da75477b17dde7f44122c41c3b | 881   | 1236   |
| 1239642039503.jpg | cdc0e5f8351c7b190f27b5452da40e29 | 600   | 540    |
| 1239642042452.jpg | 5f4123fdf1aae8a5e26876761f20c17c | 407   | 405    |
| 1239642044911.jpg | a65944cf224022426e7c959e5017bd83 | 313   | 500    |
| 1239642045388.jpg | a9f32fa77d059d515c53c151a535f49f | 640   | 342    |
| 1239642045716.jpg | 600f427fa525222538889a843edb45b1 | 480   | 640    |
| 1239642047695.jpg | be4396ca231a3cd363483e27c8911464 | 435   | 625    |
| 1239642050263.png | 51bedfb85f01b34f8338f29492800cc4 | 901   | 538    |
| 1239642063400.jpg | 3815c2c4929a2b5fd0ea85a0b50c2b19 | 469   | 297    |
| 1239642065678.jpg | 1fcd8f583ea7080c18ddef9dc0e3bdc8 | 612   | 816    |
| 1239642067773.jpg | afb15e7adbf9a8cc7af801d311fefac4 | 450   | 287    |
| 1239642071811.jpg | 42ac9aabd18996eeeca790a1f6f3a460 | 834   | 1200   |
| 1239642076646.jpg | 3d5741c33476be17b1856a4619d26166 | 492   | 370    |
| 1239642083927.jpg | 05f26039eb45647842937ff2e3dd48ec | 1920  | 2576   |
| 1239642095095.jpg | 6978f1dd9812ceb682bc3e1a93dce724 | 600   | 449    |
| 1239642105383.jpg | 0f67bb8adb74573c26b5d88a458572f1 | 834   | 1200   |
| 1239642109318.jpg | 0737fc2429e6819ca2844d642933b82e | 500   | 346    |
| 1239642112126.jpg | da391b6c8b68516dea67685755ebcfe9 | 600   | 450    |
| 1239642113695.jpg | 79f692bdf914945e31d64bd97dbc169f | 640   | 480    |
+-------------------+----------------------------------+-------+--------+
20 rows in set (1.00 sec)
                                              
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by: wuff1ukPosted on 2009-09-16 at 14:42:10ID: 25350508

This means the sorting of the query takes 3-6 seconds wheras the query itself takes 1 second. There isn't anything more that can be optimized with the query itself. The only thing left to tweak would be the mysql configuration itself by increasing buffers to prevent the impact of the order by clause.

You should try increasing your sort_buffer_size to prevent the sort to be done in a temporary table on the disk instead of in ram. Increasing read_buffer_size and read_rnd_buffer_size may also help speed up the query and the sort.

20120131-EE-VQP-002

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