Datasette provides a number of configuration options. These can be set using the
--config name:value option to
You can set multiple configuration options at once like this:
datasette mydatabase.db --config default_page_size:50 \ --config sql_time_limit_ms:3500 \ --config max_returned_rows:2000
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.
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:
datasette mydatabase.db --config default_page_size:50
By default, queries have a time limit of one second. If a query takes longer than this to run Datasette will terminate the query and return an error.
If this time limit is too short for you, you can customize it using the
sql_time_limit_ms limit - for example, to increase it to 3.5 seconds:
datasette mydatabase.db --config sql_time_limit_ms:3500
You can optionally set a lower time limit for an individual query using the
?_timelimit=100 query string argument:
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.
You can increase or decrease this limit like so:
datasette mydatabase.db --config max_returned_rows:2000
Maximum number of threads in the thread pool Datasette uses to execute SQLite queries. Defaults to 3.
datasette mydatabase.db --config num_sql_threads:10
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.
Here’s how to disable this feature:
datasette mydatabase.db --config allow_facet:off
The default number of unique rows returned by Facets is 30. You can customize it like this:
datasette mydatabase.db --config default_facet_size:50
This is the time limit Datasette allows for calculating a facet, which defaults to 200ms:
datasette mydatabase.db --config facet_time_limit_ms:1000
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.
You can increase this time limit like so:
datasette mydatabase.db --config facet_suggest_time_limit_ms:500
Should Datasette calculate suggested facets? On by default, turn this off like so:
datasette mydatabase.db --config suggest_facets:off
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:
datasette mydatabase.db --config allow_download:off
Enable/disable the ability for users to run custom SQL directly against a database. To disable this feature, run:
datasette mydatabase.db --config allow_sql:off
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).
datasette mydatabase.db --config default_cache_ttl:10
Sets the amount of memory SQLite uses for its per-connection cache, in KB.
datasette mydatabase.db --config cache_size_kb:5000
Enables the CSV export feature where an entire table (potentially hundreds of thousands of rows) can be exported as a single CSV file. This is turned on by default - you can turn it off like this:
datasette mydatabase.db --config allow_csv_stream:off
The maximum size of CSV that can be exported, in megabytes. Defaults to 100MB. You can disable the limit entirely by settings this to 0:
datasette mydatabase.db --config max_csv_mb:0
In the HTML table view, truncate any strings that are longer than this value. The full value will still be available in CSV, JSON and on the individual row HTML page. Set this to 0 to disable truncation.
datasette mydatabase.db --config truncate_cells_html:0
Forces self-referential URLs in the JSON output to always use the
protocol. This is useful for cases where the application itself is hosted using
HTTP but is served to the outside world via a proxy that enables HTTPS.
datasette mydatabase.db --config force_https_urls:1