Metadata¶
Data loves metadata. Any time you run Datasette you can optionally include a JSON file with metadata about your databases and tables. Datasette will then display that information in the web UI.
Run Datasette like this:
datasette database1.db database2.db --metadata metadata.json
Your metadata.json
file can look something like this:
{
"title": "Custom title for your index page",
"description": "Some description text can go here",
"license": "ODbL",
"license_url": "https://opendatacommons.org/licenses/odbl/",
"source": "Original Data Source",
"source_url": "http://example.com/"
}
The above metadata will be displayed on the index page of your Datasette-powered site. The source and license information will also be included in the footer of every page served by Datasette.
Any special HTML characters in description
will be escaped. If you want to
include HTML in your description, you can use a description_html
property
instead.
Per-database and per-table metadata¶
Metadata at the top level of the JSON will be shown on the index page and in the footer on every page of the site. The license and source is expected to apply to all of your data.
You can also provide metadata at the per-database or per-table level, like this:
{
"databases": {
"database1": {
"source": "Alternative source",
"source_url": "http://example.com/",
"tables": {
"example_table": {
"description_html": "Custom <em>table</em> description",
"license": "CC BY 3.0 US",
"license_url": "https://creativecommons.org/licenses/by/3.0/us/"
}
}
}
}
}
Each of the top-level metadata fields can be used at the database and table level.
Specifying units for a column¶
Datasette supports attaching units to a column, which will be used when displaying values from that column. SI prefixes will be used where appropriate.
Column units are configured in the metadata like so:
{
"databases": {
"database1": {
"tables": {
"example_table": {
"units": {
"column1": "metres",
"column2": "Hz"
}
}
}
}
}
}
Units are interpreted using Pint, and you can see the full list of available units in Pint’s unit registry. You can also add custom units to the metadata, which will be registered with Pint:
{
"custom_units": [
"decibel = [] = dB"
]
}
Setting which columns can be used for sorting¶
Datasette allows any column to be used for sorting by default. If you need to
control which columns are available for sorting you can do so using the optional
sortable_columns
key:
{
"databases": {
"database1": {
"tables": {
"example_table": {
"sortable_columns": [
"height",
"weight"
]
}
}
}
}
}
This will restrict sorting of example_table
to just the height
and
weight
columns.
You can also disable sorting entirely by setting "sortable_columns": []
By default, database views in Datasette do not support sorting. You can use sortable_columns
to enable specific sort orders for a view called name_of_view
in the database my_database
like so:
{
"databases": {
"my_database": {
"tables": {
"name_of_view": {
"sortable_columns": [
"clicks",
"impressions"
]
}
}
}
}
}
Specifying the label column for a table¶
Datasette’s HTML interface attempts to display foreign key references as labelled hyperlinks. By default, it looks for referenced tables that only have two columns: a primary key column and one other. It assumes that the second column should be used as the link label.
If your table has more than two columns you can specify which column should be
used for the link label with the label_column
property:
{
"databases": {
"database1": {
"tables": {
"example_table": {
"label_column": "title"
}
}
}
}
}
Hiding tables¶
You can hide tables from the database listing view (in the same way that FTS and
Spatialite tables are automatically hidden) using "hidden": true
:
{
"databases": {
"database1": {
"tables": {
"example_table": {
"hidden": true
}
}
}
}
}
Generating a metadata skeleton¶
Tracking down the names of all of your databases and tables and formatting them as JSON can be a little tedious, so Datasette provides a tool to help you generate a “skeleton” JSON file:
datasette skeleton database1.db database2.db
This will create a metadata.json
file looking something like this:
{
"title": null,
"description": null,
"description_html": null,
"license": null,
"license_url": null,
"source": null,
"source_url": null,
"databases": {
"database1": {
"title": null,
"description": null,
"description_html": null,
"license": null,
"license_url": null,
"source": null,
"source_url": null,
"queries": {},
"tables": {
"example_table": {
"title": null,
"description": null,
"description_html": null,
"license": null,
"license_url": null,
"source": null,
"source_url": null,
"units": {}
}
}
},
"database2": ...
}
}
You can replace any of the null
values with a JSON string to populate that
piece of metadata.