Core (Data Model) of WordPress Core

The Core of WordPress CoreDigging Into WordPress’s Core Data Model

@jakemgold

• President of 10up - a growing WordPress-centric agency with 18 full time employees

• Clients like Juicy Couture, Time Inc, Condé Nast, Consumer Reports, TechCrunch, Universal Sports, Trulia, & More

• 10 of our 13 software engineers (including me!) contributed to WordPress 3.5, and we maintain some of the best rated, most downloaded plug-ins.

• Personal background: 15 years in web development, with a concentration in information systems & architecture

Premise

As a content management framework, WordPress mostly conceals abstract database complexity from us. Cool.

$args = array(

'post_type' => 'my_custom_post_type',

'meta_key' => 'age',

'orderby' => 'meta_value_num',

'order' => 'ASC',

'meta_query' => array(

array( 'key' =>

'age',

'value' => array(3, 4),

'compare' => 'IN',

) ) ); $query = new WP_Que

ry($args);

SELECT * FROM

... blah blah blah ...

Premise

As a result, few consider how WordPress stores all the things when you peel the software layer back.

Less cool.

$args = array(

'meta_key' => 'age',

'order' => 'ASC',

'meta_query' => array(

array( 'key' =>

'age',

'compare' => 'IN',

) ) ); $query = new WP_Que

ry($args);

SELECT * FROM

Premise

As a result, few consider how WordPress stores all the things when you peel the software layer back.

Less cool.

SELECT * FROM

Premise

Studying how “the things” are stored (the data model) and its evolution empowers us to understand WordPress, its

potential, and its limitations in deeper ways.

SELECT * FROM

Premise

Studying how “the things” are stored (the data model) and its evolution empowers us to understand WordPress, its

potential, and its limitations in deeper ways.

SELECT * FROM

On Platforms & Abstraction

Good platforms make it easy to build stuff it wasn’t explicitly designed for.

Good content platforms make it easy to create content it wasn’t explicitly designed for.

On Abstraction

If we wanted to build an application to manage project tasks, its data

model might look like this.

On Abstraction

If we wanted to build an application to manage project tasks, its data

model might look like this.

If we were building a platform that could be used for project tasks, or any other kind of content, it would

look very different.

On Abstraction

WordPress’s data model essentially handles abstraction with:One fairly generic content object table: wp_posts

Field TypeID bigint(20) unsignedpost_author bigint(20) unsignedpost_date datetimepost_date_gmt datetimepost_content longtextpost_title textpost_excerpt textpost_status varchar(20)comment_status varchar(20)ping_status varchar(20)post_password varchar(20)post_name varchar(200)to_ping textpinged textpost_modified datetimepost_modified_gmt datetimepost_content_filtered longtextpost_parent bigint(20) unsignedguid varchar(255)menu_order int(11)post_type varchar(20)post_mime_type varchar(100)comment_count bigint(20)

post_contentgeneric field for content

post_statusgeneric field for identifier of

state of content object

post_parentobject hierarchy

menu_orderrelative order of content

post_type (!!!)generic identifier for type of

content object

post_mime_typestandards based identifier of

the type of information contained in content

WordPress’s data model essentially handles abstraction with:A completely abstract content object properties table: wp_postmeta

Field Type

meta_id bigint(20)

post_id bigint(20)

meta_key varchar(255)

meta_value text

Meta data is defined as “data about data.”It doesn’t get more abstract.

Field Type

meta_id bigint(20)

post_id bigint(20)

meta_value text

identifier of content objectthis is all about

Field Type

meta_id bigint(20)

post_id bigint(20)

meta_value text

arbitrary identifier for the content property we want

to define

Field Type

meta_id bigint(20)

post_id bigint(20)

meta_value text

arbitrary value for ourarbitrary property

WordPress’s data model essentially handles abstraction with:An abstract set of tables for content classification.

Field Type

term_id bigint(20) unsigned

name varchar(200)

slug varchar(200)

term_group bigint(10)

wp_termsArbitrary classifications for content objects.

Field Type

name varchar(200)

slug varchar(200)

Field Type

term_taxonomy_id bigint(20) unsigned

taxonomy varchar(32)

description longtext

parent bigint(20) unsigned

count bigint(20)

wp_term_taxonomyDescribes the arbitrary classification (term) for each unique classification group (taxonomy).

Field Type

name varchar(200)

slug varchar(200)

Field Type

count bigint(20)

Field Type

object_id bigint(20) unsigned

term_order int(11)

wp_term_relationshipsAssociates classifications with content objects.

Field Type

name varchar(200)

slug varchar(200)

Field Type

count bigint(20)

Huh?... oops.

Field Type

term_order int(11)

Anything else here surprise you?

Field Type

term_order int(11)

term_order (??)WordPress’s API does not support ordering terms. Its data model actually does.

Field Type

term_order int(11)

term_order (??)WordPress’s API does not support ordering terms. Its data model actually does.

Where’s term meta?The data model doesn’t yet

(really) support arbitrary data about a classification / term.

WordPress’s data model essentially handles abstraction with:A completely abstract global data table: wp_options

Field Type

option_id bigint(20) unsigned

option_name varchar(64)

option_value longtext

autoload varchar(20)

Field Type

arbitrary name of data

Field Type

arbitrary value for said data

Other tables and abstraction!

wp_comments & wp_commentmetaComments are a specific type of content object, separated

for legacy and scalability reasons.

wp_users & wp_usermetaUsers a special object (not really content). Also have arbitrary properties / meta data.

wp_linksA specific content object (and leftover.)

How did we get here?

Why do we call content objects “posts”?

And why the heck is there a “links” table?

WordPress 1.5: Blogging Software

Tables:wp_categorieswp_comments

wp_linkcategorieswp_links

wp_optionswp_post2catwp_postmeta

wp_postswp_users

WordPress 1.5*: Blogging Software

wp_postswp_users

Field TypeID bigint(20) unsignedpost_author int(4)post_date datetimepost_date_gmt datetimepost_content longtextpost_title textpost_category int(4)post_excerpt textpost_status enum('publish','draft','private','static','object')comment_status enum('open','closed','registered_only')ping_status enum('open','closed')post_password varchar(20)post_name varchar(200)to_ping textpinged textpost_modified datetimepost_modified_gmt datetimepost_content_filtered textpost_parent int(11)guid varchar(255)menu_order int(11)

wp_postswp_users

Field Type

meta_id bigint(20)

post_id bigint(20)

meta_value text

wp_postswp_users

Field Type

meta_id bigint(20)

post_id bigint(20)

meta_value text

Arbitrary content (post) meta data!Early sign of data model

abstraction... and possibility!

WordPress 2.0: Foundation for Content Abstraction

wp_postswp_usermeta

wp_users

Field TypeID bigint(20) unsignedpost_author bigint(20)post_date datetimepost_date_gmt datetimepost_content longtextpost_title textpost_category int(4)post_excerpt textpost_status enum('publish','draft','private','static','object', 'attachment')

comment_status enum('open','closed','registered_only')ping_status enum('open','closed')post_password varchar(20)post_name varchar(200)to_ping textpinged textpost_modified datetimepost_modified_gmt datetimepost_content_filtered textpost_parent bigint(20)guid varchar(255)menu_order int(11)post_type varchar(100)post_mime_type varchar(100)comment_count bigint(20)

WordPress 2.0: Foundation for Content Abstraction

wp_postswp_usermeta

wp_users

Field TypeID bigint(20) unsignedpost_author bigint(20)post_date datetimepost_date_gmt datetimepost_content longtextpost_title textpost_category int(4)post_excerpt textpost_status enum('publish','draft','private','static','object', 'attachment')

comment_status enum('open','closed','registered_only')ping_status enum('open','closed')post_password varchar(20)post_name varchar(200)to_ping textpinged textpost_modified datetimepost_modified_gmt datetimepost_content_filtered textpost_parent bigint(20)guid varchar(255)menu_order int(11)post_type varchar(100)post_mime_type varchar(100)comment_count bigint(20)

Origin: Pages & Media.Post type API wouldn’t

come till 3.0!

WordPress 2.0: Foundation for Content Types

wp_postswp_usermeta

wp_users

WordPress 2.0: Foundation for Content Types

wp_postswp_usermeta

wp_users

Field Type

umeta_id bigint(20)

user_id bigint(20)

meta_value longtext

User objects are now extensible with arbitrary meta data.

More signs of extensibility!

WordPress 2.3: Classifications Get Abstract

Tables:wp_comments

wp_linkswp_options

wp_postmetawp_postswp_terms

wp_term_relationshipswp_term_taxonomy

wp_usermetawp_users

Removed Tables:wp_categories

wp_linkcategorieswp_post2cat

WordPress 2.3: Classifications Get Abstract

Tables:wp_comments

wp_linkswp_options

wp_postmetawp_postswp_terms

wp_usermetawp_users

Removed Tables:wp_categories

wp_linkcategorieswp_post2cat

Impetus: Tags.Taxonomy registration API

wouldn’t come till 2.9!

Category fields in post and links tables don’t get removed

until 2.8.

WordPress 2.5: Enum Values Fade Away

post_status, comment_status, ping_statusin wp_posts table change from enumerated list (enforced options

in data model) to freeform field

term_order curiously gets added to wp_term_relationships table

WordPress 2.9: Comment Objects Get Meta

Tables:wp_comments

wp_commentmetawp_links

wp_optionswp_postmeta

wp_postswp_terms

wp_usermetawp_users

WordPress 3.0: Groups of Objects

more detail: http://codex.wordpress.org/Database_Description/2.0

WordPress Network Mode (Multisite)

(which we’re not going to study for time’s sake)

The Future of WordPress’s Data Model

• Clean up of taxonomy tables, and addition of term meta data?

• Legacy specific content object tables (links) fall away? (note 3.5)

• Post table fields very specific to blog posts get moved over to post meta or taxonomies?

• Improvements to relationships between content objects?

The Core of WordPress CoreThanks! Slides will be available at 10up.com.

Feedback? Want more? @jakemgold on Twitter

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