activity-stream/metadata_schema.md

The metadata database in Activity Stream stores information about pages and their images in the following tables.

Metadata Table

A row in this table represents the metadata of a single page which has been visited 1 or more times by the user.

field	type	description
id	Int	auto incrementing primary key
cache_key	String (Unique)	A simplified URL which is shared across multiple places URLs (ie protocol removed, query string reduced/removed)
places_url	String	The unmodified URL which appears in the PlacesDB when a user visits a page
title	String	The title of the page
type	String	The og:type tag ie 'article', 'video', 'page', etc
description	String	The meta description of the page
media_url	String	The URL for an embedded media item (audio/video)
created_at	datetime	The date and time that this metadata row was inserted/created
expired_at	Long	The date and time this metadata row will expire

Images Table

A row in this table represents a single image which appears on a page visited by a user, including favicons and rich icons. Each row in the metadata table will have multiple corresponding images in this table. A single row in this table may belong to multiple metadata page rows, ie a favicon which is identical for multiple pages.

field	type	description
id	Int	auto incrementing primary key
type	Int	The type of the image, initial types are: favicon 1, rich_icon 2, preview 3 (constants)
url	String	The URL for the image
height	Int	The height of the image in pixels
width	Int	The width of the image in pixels
color	String	The dominant/aggregate color of the image

MetadataImage Join Table

A row in this table represents a pair of a metadata row and an image row which indicates that that image appears on that page.

field	type	description
metadata_id	Int	A foreign key onto the Metadata table
image_id	Int	A foreign key onto the Images table