To prevent rogue, long-running queries from making a Datasette instance inaccessible to other users, Datasette imposes some limits on the SQL that you can execute. These are exposed as config options which you can over-ride.
default_page_size
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The default number of rows returned by the table page. You can over-ride this on a per-page basis using the ``?_size=80`` querystring parameter, provided you do not specify a value higher than the ``max_returned_rows`` setting. You can set this default using ``--config`` like so::
This would set the time limit to 100ms for that specific query. This feature is useful if you are working with databases of unknown size and complexity - a query that might make perfect sense for a smaller table could take too long to execute on a table with millions of rows. By setting custom time limits you can execute queries "optimistically" - e.g. give me an exact count of rows matching this query but only if it takes less than 100ms to calculate.
Datasette returns a maximum of 1,000 rows of data at a time. If you execute a query that returns more than 1,000 rows, Datasette will return the first 1,000 and include a warning that the result set has been truncated. You can use OFFSET/LIMIT or other methods in your SQL to implement pagination if you need to return more than 1,000 rows.
Allow users to specify columns they would like to facet on using the ``?_facet=COLNAME`` URL parameter to the table view.
This is enabled by default. If disabled, facets will still be displayed if they have been specifically enabled in ``metadata.json`` configuration for the table.
When Datasette calculates suggested facets it needs to run a SQL query for every column in your table. The default for this time limit is 50ms to account for the fact that it needs to run once for every column. If the time limit is exceeded the column will not be suggested as a facet.
Should users be able to download the original SQLite database using a link on the database index page? This is turned on by default - to disable database downloads, use the following::
Default HTTP caching max-age header in seconds, used for ``Cache-Control: max-age=X``. Can be over-ridden on a per-request basis using the ``?_ttl=`` querystring parameter. Set this to ``0`` to disable HTTP caching entirely. Defaults to 365 days (31536000 seconds).