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--limit= mechanism plus new limits for facets

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Replaced the --max_returned_rows and --sql_time_limit_ms options to
"datasette serve" with a new --limit option, which supports a larger
list of limits.

Example usage:

	datasette serve --limit max_returned_rows:1000 \
		--limit sql_time_limit_ms:2500 \
		--limit default_facet_size:50 \
		--limit facet_time_limit_ms:1000 \
		--limit facet_suggest_time_limit_ms:500

New docs: https://datasette.readthedocs.io/en/latest/limits.html

Closes #270
Closes #264
This commit is contained in:
Simon Willison 2018-05-17 22:08:26 -07:00
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33
docs/sql_queries.rst
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@ -46,39 +46,6 @@ statements can be used to change database settings at runtime. If you need to
include the string "pragma" in a query you can do so safely using a named
parameter.
Query limits
------------
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.
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`` option - for example, to increase it to 3.5 seconds::
datasette mydatabase.db --sql_time_limit_ms=3500
You can optionally set a lower time limit for an individual query using the
``_timelimit`` query string argument::
/my-database/my-table?qSpecies=44&_timelimit=100
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.
Views
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