PHP Performance 101:so you need to use a database

Leon Fayer@papa_fire

Who am I ?

• 20+ years development and operations of web applications

• currently Vice President at OmniTI

• can be found online:

• @papa_fire

• github:lfayer

• http://fayerplay.com

• https://joind.in/talk/view/11914

what it is about

databases & performance

what it’s not about

NoSQL MySQL

how database connection works

① establish connection

② send query

③ process query

④ send result

⑤ close connection

common database connection

$dbh = new DB(…);

$sth = $dbh->prepare($query);

$sth->execute();

$result = $sth->fetchAll();

$dbh = null;

common database connection

① var $dbh = new DB(…);

② var $sth = $dbh->prepare($query);

① $sth->execute();

② var $result = $sth->fetchAll();

③ $dbh = null;

① establish connection

① establish connection

⑤ close connection

and

problem

connection overhead

visual representation

①

①

①

⑤

⑤

⑤

short answer

persistent connections

short and helpful answer

persistent connections

avoid multiple connections

how it works (high level)

①

①

①

⑤

⑤

⑤

①

⑤

conclusion

reduce # of connections

② send query

most common problem

n+1

n+1

// get a list of items

$sth = $dbh->prepare("select item_id from items

where active = true");

$sth->execute();

$items = $sth->fetchAll();

// get properties for each items

foreach ($items as $i) {

$sth_prop = $dbh->prepare("select * from

item_properties where item_id = ?");

$sth_prop->execute($item);

$item_list[$i[‘item_id’]][‘props’] = $sth_prop->fetchAll();

$item_list[$i[‘item_id’]][‘id’] = $i[‘id’];

}

n+1 you don’t know about

// get a list of items

$items = get_active_item_ids();

// get properties for each items

foreach ($items as $i) {

$item = Item->new($i[‘item_id’])

$item_list[$i[‘item_id’][‘id’] = $item->item_id;

$item_list[$i[‘item_id’]][‘props’] = $item->properties();

}

easy solution

// get a list of items with properties

$sth = $dbh->prepare("select i. item_id, p.* from items i,

item_properties p

where i.item_id = p.item_id

and active = true");

$sth->execute();

$items = $sth->fetchAll();

// arrange object to your liking

foreach ($items as $i) {

$item_list[$i[‘item_id’]][‘props’] = $i;

$item_list[$i[‘item_id’]][‘id’] = $i[‘id’];

}

conclusion

limit number of queries

cool stuff

:BONUS:Common Table Expressions

(CTEs)

* MySQL does not support CTEs

// create temp table naughty_users

// and get data from it

with naughty_users as (

select * from users where banned = 1

)

select userid, email from naughty_users;

even more cool

Writeable

Common Table Expressions

* Postgres 9.1+ only

multiple queries are required

// create user record

insert into users (name, email) values (?,?) returning

userid

// create address record

insert into addresses (userid, address, city, state,

zip) values (?,?,?,?,?) returning addressid

// track changes to user information

insert into user_history (userid, addressid, action)

values (?,?,?) returning historyid

or are they?

with userdata as (

insert into users (name, email) values (?,?)

returning userid

), addressdata as (

insert into addresses (userid, address, city, state, zip)

select userid,?,?,?,? from userdata

returning addressid

), historydata as (

insert into user_history (userid, addressid, action)

select userid, addressid,?

from userdata, addressdata

returning historyid

)

select userid, addressid, historyid

from userdata, addressdata, historydata;

why not use transactions?

• no complicated transaction code

• no complicated error handling code

• reduced query overhead

• better performance

find out more

For more details:

http://omniti.com/seeds/writable-ctes-improve-performance

③ process query

unpopular opinion

ORMs are evil

why?

1. machine-generated

2. object construction overhead

3. false sense of control

in one sentence

you have no idea how it works

timely tweet

conclusion

learn SQL

④ send results

may be shocking, but …

databases can do math

illustrating wrong// get all orders

$sth = $dbh->prepare("select order_id, price from orders");

$sth->execute();

$orders= $sth->fetchAll();

//order by order_id

usort($orders, function ($a, $b) { if ($a['order_id'] == $b['order_id']) { return 0; }

return $a['order_id'] < $b['order_id'] ? -1 : 1; });

// get average $ for last 10 orders

$count = 1;

$total = 0;

$avg = 0;

foreach ($orders as $order) {

$total += $order[‘price’];

if ($count == 10) {

$avg = $total/$count;

break 1;

}

$count++;

}

vs right

// get average $ for last 10 orders

$sth = $dbh->prepare("select avg(price) as avg_price

from (select price from orders

order by order_id desc limit 10) ");

$sth->execute();

$orders= $sth->fetchAll();

$avg = $orders[‘avg_price’];

conclusion

learn SQL

other things to consider

1. cache is a wonderful thing

2. * is not your friend

3. EXPLAIN/ANALYZE are

Questions?