PHP  +  MySQL  Optimization  

Introduction •  The report includes project-related (EU) queries, tables

or databases example. •  We can learn simple php/mysql optimization. •  Know the main idea of using index in a table.

Let’s start from simple cases

Let’s start from simple cases

Avoid excess variables function  isSomething()  {                  $is_something  =  false;                    if  ($some_condition_happens)  {                            $is_something  =  true;                    }                      return  $is_something;  }  

Let’s start from simple cases

Use cache (eg. APC, memcache)

Let’s start from simple cases

Avoid queries inside a loop.

$player_ids = array(1, 2, 3, 4, 5, 6, 7, 8); foreach ($player_ids as $id) { $players_infos[] = $db->query(“SELECT * FROM player WHERE id = ?”, array($id)); }

Let’s start from simple cases

Select only needed columns.

Let’s start from simple cases

count(*) vs count(col_name)

Let’s start from simple cases

limit 1 when retrieving a

unique row.

Index to remember

Index to remember

Without an index, MySQL must begin

with the first row and then read through the entire table to find the relevant rows.

Index to remember

If there is a choice between multiple

indexes, MySQL normally uses the index that finds the smallest number of rows

Index to remember

To retrieve rows from other tables when performing joins, MySQL can use indexes on columns more efficiently if they are declared as the same type and size.

(Comparison of dissimilar columns may prevent use of indexes if values cannot be compared directly without conversion.)

Index to remember

“Index has significant cost. So you should not create index everywhere.”

- http://lab.klab.org/

mysql-bootcamp/key.html

Examples

Examples Scenario : Imagine you have a table that will

store millions of records (eg. item_history) and you don’t have indexes.

Examples The table structure :

id int(10) unsigned

player_id int(10) unsigned

item_master_id int(10) unsigned

type enum('INC','DEC')

reason varchar(255)

num smallint(5) unsigned

purchase_history_id int(10) unsigned created

timestamp

Examples

The problem : When you try to select data from a table without index

See how many rows were checked after the search?

Examples

The solution : We are going to add index for the player_id column

ALTER TABLE `item_history` ADD INDEX ( `player_id` )

See the advantage of adding an index? The search took 1 row search only.

Examples

Upon looking on the table structure which column/s can be used as index when you want to retrieved a player’s item history?

Exercise Table Name : unit_history

Description : Tracks player’s record when he/she gained, evolved, etc.. a unit.

Table structure :

id int(10) player_id int(10) unit_master_id int(10) type enum(‘INC’, ‘DEC’, ‘EVOLVED’, ‘EXP’,

‘ITEM’) created timestamp

Exercise

The Scenario : List player ids who gained and evolved the unit

id 10

The Question : What are the possible index we might need in

order to retrieve the data faster.

Using index in joins

•  columns that you will use as the join condition ( ON a.id = b.id ) should be indexed.

•  LEFT JOIN will use indexed column from left ( a.id )

•  RIGHT JOIN will use indexed column from right ( b.id )

Did you know?

That we MySQL has a built-in profiling tool?

SET PROFILING = 1; SELECT COUNT(*) FROM table_name WHERE id = 1; SHOW PROFILE FOR QUERY 1;

SHOW PROFILES;