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ReStructuredText
.. _metadata:
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Metadata
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========
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Data loves metadata. Any time you run Datasette you can optionally include a
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YAML or JSON file with metadata about your databases and tables. Datasette will then
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display that information in the web UI.
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Run Datasette like this::
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datasette database1.db database2.db --metadata metadata.yaml
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Your ``metadata.yaml`` file can look something like this:
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.. [[[cog
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from metadata_doc import metadata_example
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metadata_example(cog, {
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"title": "Custom title for your index page",
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"description": "Some description text can go here",
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"license": "ODbL",
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"license_url": "https://opendatacommons.org/licenses/odbl/",
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"source": "Original Data Source",
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"source_url": "http://example.com/"
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})
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.. ]]]
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.. tab:: metadata.yaml
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.. code-block:: yaml
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title: Custom title for your index page
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description: Some description text can go here
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license: ODbL
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license_url: https://opendatacommons.org/licenses/odbl/
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source: Original Data Source
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source_url: http://example.com/
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.. tab:: metadata.json
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.. code-block:: json
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{
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"title": "Custom title for your index page",
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"description": "Some description text can go here",
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"license": "ODbL",
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"license_url": "https://opendatacommons.org/licenses/odbl/",
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"source": "Original Data Source",
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"source_url": "http://example.com/"
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}
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.. [[[end]]]
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Choosing YAML over JSON adds support for multi-line strings and comments.
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The above metadata will be displayed on the index page of your Datasette-powered
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site. The source and license information will also be included in the footer of
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every page served by Datasette.
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Any special HTML characters in ``description`` will be escaped. If you want to
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include HTML in your description, you can use a ``description_html`` property
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instead.
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Per-database and per-table metadata
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-----------------------------------
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Metadata at the top level of the file will be shown on the index page and in the
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footer on every page of the site. The license and source is expected to apply to
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all of your data.
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You can also provide metadata at the per-database or per-table level, like this:
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.. [[[cog
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metadata_example(cog, {
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"databases": {
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"database1": {
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"source": "Alternative source",
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"source_url": "http://example.com/",
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"tables": {
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"example_table": {
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"description_html": "Custom <em>table</em> description",
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"license": "CC BY 3.0 US",
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"license_url": "https://creativecommons.org/licenses/by/3.0/us/"
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}
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}
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}
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}
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})
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.. ]]]
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.. tab:: metadata.yaml
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.. code-block:: yaml
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databases:
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database1:
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source: Alternative source
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source_url: http://example.com/
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tables:
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example_table:
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description_html: Custom <em>table</em> description
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license: CC BY 3.0 US
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license_url: https://creativecommons.org/licenses/by/3.0/us/
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.. tab:: metadata.json
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.. code-block:: json
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{
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"databases": {
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"database1": {
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"source": "Alternative source",
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"source_url": "http://example.com/",
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"tables": {
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"example_table": {
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"description_html": "Custom <em>table</em> description",
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"license": "CC BY 3.0 US",
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"license_url": "https://creativecommons.org/licenses/by/3.0/us/"
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}
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}
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}
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}
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}
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.. [[[end]]]
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Each of the top-level metadata fields can be used at the database and table level.
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.. _metadata_source_license_about:
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Source, license and about
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-------------------------
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The three visible metadata fields you can apply to everything, specific databases or specific tables are source, license and about. All three are optional.
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**source** and **source_url** should be used to indicate where the underlying data came from.
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**license** and **license_url** should be used to indicate the license under which the data can be used.
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**about** and **about_url** can be used to link to further information about the project - an accompanying blog entry for example.
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For each of these you can provide just the ``*_url`` field and Datasette will treat that as the default link label text and display the URL directly on the page.
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.. _metadata_column_descriptions:
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Column descriptions
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-------------------
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You can include descriptions for your columns by adding a ``"columns": {"name-of-column": "description-of-column"}`` block to your table metadata:
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.. [[[cog
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metadata_example(cog, {
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"databases": {
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"database1": {
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"tables": {
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"example_table": {
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"columns": {
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"column1": "Description of column 1",
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"column2": "Description of column 2"
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}
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}
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}
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}
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}
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})
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.. ]]]
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.. tab:: metadata.yaml
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.. code-block:: yaml
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databases:
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database1:
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tables:
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example_table:
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columns:
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column1: Description of column 1
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column2: Description of column 2
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.. tab:: metadata.json
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.. code-block:: json
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{
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"databases": {
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"database1": {
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"tables": {
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"example_table": {
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"columns": {
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"column1": "Description of column 1",
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"column2": "Description of column 2"
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}
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}
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}
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}
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}
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}
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.. [[[end]]]
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These will be displayed at the top of the table page, and will also show in the cog menu for each column.
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You can see an example of how these look at `latest.datasette.io/fixtures/roadside_attractions <https://latest.datasette.io/fixtures/roadside_attractions>`__.
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Specifying units for a column
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-----------------------------
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Datasette supports attaching units to a column, which will be used when displaying
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values from that column. SI prefixes will be used where appropriate.
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Column units are configured in the metadata like so:
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.. [[[cog
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metadata_example(cog, {
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"databases": {
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"database1": {
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"tables": {
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"example_table": {
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"units": {
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"column1": "metres",
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"column2": "Hz"
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}
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}
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}
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}
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}
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})
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.. ]]]
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.. tab:: metadata.yaml
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.. code-block:: yaml
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databases:
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database1:
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tables:
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example_table:
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units:
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column1: metres
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column2: Hz
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.. tab:: metadata.json
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.. code-block:: json
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{
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"databases": {
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"database1": {
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"tables": {
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"example_table": {
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"units": {
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"column1": "metres",
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"column2": "Hz"
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}
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}
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}
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}
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}
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}
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.. [[[end]]]
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Units are interpreted using Pint_, and you can see the full list of available units in
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Pint's `unit registry`_. You can also add `custom units`_ to the metadata, which will be
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registered with Pint:
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.. [[[cog
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metadata_example(cog, {
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"custom_units": [
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"decibel = [] = dB"
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]
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})
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.. ]]]
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.. tab:: metadata.yaml
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.. code-block:: yaml
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custom_units:
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- decibel = [] = dB
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.. tab:: metadata.json
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.. code-block:: json
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{
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"custom_units": [
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"decibel = [] = dB"
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]
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}
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.. [[[end]]]
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.. _Pint: https://pint.readthedocs.io/
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.. _unit registry: https://github.com/hgrecco/pint/blob/master/pint/default_en.txt
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.. _custom units: http://pint.readthedocs.io/en/latest/defining.html
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.. _metadata_default_sort:
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Setting a default sort order
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----------------------------
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By default Datasette tables are sorted by primary key. You can over-ride this default for a specific table using the ``"sort"`` or ``"sort_desc"`` metadata properties:
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.. [[[cog
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metadata_example(cog, {
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"databases": {
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"mydatabase": {
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"tables": {
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"example_table": {
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"sort": "created"
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}
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}
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}
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}
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})
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.. ]]]
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.. tab:: metadata.yaml
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.. code-block:: yaml
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databases:
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mydatabase:
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tables:
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example_table:
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sort: created
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.. tab:: metadata.json
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.. code-block:: json
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{
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"databases": {
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"mydatabase": {
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"tables": {
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"example_table": {
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"sort": "created"
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}
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}
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}
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}
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}
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.. [[[end]]]
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Or use ``"sort_desc"`` to sort in descending order:
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.. [[[cog
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metadata_example(cog, {
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"databases": {
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"mydatabase": {
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"tables": {
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"example_table": {
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"sort_desc": "created"
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}
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}
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}
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}
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})
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.. ]]]
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.. tab:: metadata.yaml
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.. code-block:: yaml
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databases:
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mydatabase:
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tables:
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example_table:
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sort_desc: created
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.. tab:: metadata.json
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.. code-block:: json
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{
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"databases": {
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"mydatabase": {
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"tables": {
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"example_table": {
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"sort_desc": "created"
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}
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}
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}
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}
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}
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.. [[[end]]]
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.. _metadata_page_size:
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Setting a custom page size
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--------------------------
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Datasette defaults to displaying 100 rows per page, for both tables and views. You can change this default page size on a per-table or per-view basis using the ``"size"`` key in ``metadata.json``:
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.. [[[cog
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metadata_example(cog, {
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"databases": {
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"mydatabase": {
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"tables": {
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"example_table": {
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"size": 10
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}
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}
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}
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}
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})
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.. ]]]
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.. tab:: metadata.yaml
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.. code-block:: yaml
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databases:
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mydatabase:
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tables:
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example_table:
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size: 10
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.. tab:: metadata.json
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.. code-block:: json
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{
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"databases": {
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"mydatabase": {
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"tables": {
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"example_table": {
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"size": 10
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}
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}
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}
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}
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}
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.. [[[end]]]
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This size can still be over-ridden by passing e.g. ``?_size=50`` in the query string.
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.. _metadata_sortable_columns:
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Setting which columns can be used for sorting
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---------------------------------------------
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Datasette allows any column to be used for sorting by default. If you need to
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control which columns are available for sorting you can do so using the optional
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``sortable_columns`` key:
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.. [[[cog
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metadata_example(cog, {
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"databases": {
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"database1": {
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"tables": {
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"example_table": {
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"sortable_columns": [
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"height",
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"weight"
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]
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}
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}
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}
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}
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})
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.. ]]]
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.. tab:: metadata.yaml
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.. code-block:: yaml
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databases:
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database1:
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tables:
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example_table:
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sortable_columns:
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- height
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- weight
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.. tab:: metadata.json
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.. code-block:: json
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{
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"databases": {
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"database1": {
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"tables": {
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"example_table": {
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"sortable_columns": [
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"height",
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"weight"
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]
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}
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}
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}
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}
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}
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.. [[[end]]]
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This will restrict sorting of ``example_table`` to just the ``height`` and
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``weight`` columns.
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You can also disable sorting entirely by setting ``"sortable_columns": []``
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You can use ``sortable_columns`` to enable specific sort orders for a view called ``name_of_view`` in the database ``my_database`` like so:
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.. [[[cog
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metadata_example(cog, {
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"databases": {
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"my_database": {
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"tables": {
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"name_of_view": {
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"sortable_columns": [
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"clicks",
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"impressions"
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]
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}
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}
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}
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}
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})
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.. ]]]
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.. tab:: metadata.yaml
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.. code-block:: yaml
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databases:
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my_database:
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tables:
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name_of_view:
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sortable_columns:
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- clicks
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- impressions
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.. tab:: metadata.json
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.. code-block:: json
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{
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"databases": {
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"my_database": {
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"tables": {
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"name_of_view": {
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"sortable_columns": [
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"clicks",
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"impressions"
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]
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}
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}
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}
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}
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}
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.. [[[end]]]
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.. _label_columns:
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Specifying the label column for a table
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---------------------------------------
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Datasette's HTML interface attempts to display foreign key references as
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labelled hyperlinks. By default, it looks for referenced tables that only have
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two columns: a primary key column and one other. It assumes that the second
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column should be used as the link label.
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If your table has more than two columns you can specify which column should be
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used for the link label with the ``label_column`` property:
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.. [[[cog
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metadata_example(cog, {
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"databases": {
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"database1": {
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"tables": {
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"example_table": {
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"label_column": "title"
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}
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}
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}
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}
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})
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.. ]]]
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.. tab:: metadata.yaml
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.. code-block:: yaml
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databases:
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database1:
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tables:
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example_table:
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label_column: title
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.. tab:: metadata.json
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.. code-block:: json
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{
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"databases": {
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"database1": {
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"tables": {
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"example_table": {
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"label_column": "title"
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}
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}
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}
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}
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}
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.. [[[end]]]
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.. _metadata_hiding_tables:
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Hiding tables
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-------------
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You can hide tables from the database listing view (in the same way that FTS and
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SpatiaLite tables are automatically hidden) using ``"hidden": true``:
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.. [[[cog
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metadata_example(cog, {
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"databases": {
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"database1": {
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"tables": {
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"example_table": {
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"hidden": True
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}
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}
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}
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}
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})
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.. ]]]
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.. tab:: metadata.yaml
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.. code-block:: yaml
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databases:
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database1:
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tables:
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example_table:
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hidden: true
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.. tab:: metadata.json
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.. code-block:: json
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{
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"databases": {
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"database1": {
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"tables": {
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"example_table": {
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"hidden": true
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}
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}
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}
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}
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}
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.. [[[end]]]
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.. _metadata_reference:
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Metadata reference
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------------------
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A full reference of every supported option in a ``metadata.json`` or ``metadata.yaml`` file.
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Top-level metadata
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~~~~~~~~~~~~~~~~~~
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"Top-level" metadata refers to fields that can be specified at the root level of a metadata file. These attributes are meant to describe the entire Datasette instance.
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The following are the full list of allowed top-level metadata fields:
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- ``title``
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- ``description``
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- ``description_html``
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- ``license``
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- ``license_url``
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- ``source``
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- ``source_url``
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Database-level metadata
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~~~~~~~~~~~~~~~~~~~~~~~
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"Database-level" metadata refers to fields that can be specified for each database in a Datasette instance. These attributes should be listed under a database inside the `"databases"` field.
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The following are the full list of allowed database-level metadata fields:
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- ``source``
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- ``source_url``
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- ``license``
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- ``license_url``
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- ``about``
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- ``about_url``
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Table-level metadata
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~~~~~~~~~~~~~~~~~~~~
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"Table-level" metadata refers to fields that can be specified for each table in a Datasette instance. These attributes should be listed under a specific table using the `"tables"` field.
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The following are the full list of allowed table-level metadata fields:
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- ``source``
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- ``source_url``
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- ``license``
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- ``license_url``
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- ``about``
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- ``about_url``
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- ``hidden``
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- ``sort/sort_desc``
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- ``size``
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- ``sortable_columns``
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- ``label_column``
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- ``facets``
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- ``fts_table``
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- ``fts_pk``
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- ``searchmode``
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- ``columns``
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