#12545: contains and F() don't work well together
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Reporter: Matthew | Owner: nobody
Status: new | Milestone:
Component: Uncategorized | Version: 1.1
Keywords: | Stage: Unreviewed
Has_patch: 0 |
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Sorry if this is noted, I did search for a while, but it's hard to search
for "F" :) I can't see anything in the documentation saying you shouldn't
use F() with contains, especially given one of the examples is with lt.
But the following code:
{{{
from thing.models import Thing
from django.db import connection
from django.db.models import F
def do(q):
connection.queries = []
try:
list(q)
except Exception, e:
print "Exception thrown: %s" % e
print connection.queries[0]['sql']
do( Thing.objects.filter( foo='bar' ) )
do( Thing.objects.filter( foo=F('bar') ) )
do( Thing.objects.filter( foo__contains='bar' ) )
do( Thing.objects.filter( foo__contains=F('bar') ) )
}}}
gives the following (spaces tweaked for display) with sqlite3:
{{{
SELECT "thing_thing"."id", "thing_thing"."foo", "thing_thing"."bar"
FROM "thing_thing" WHERE "thing_thing"."foo" = bar
SELECT "thing_thing"."id", "thing_thing"."foo", "thing_thing"."bar"
FROM "thing_thing" WHERE "thing_thing"."foo" = "thing_thing"."bar"
SELECT "thing_thing"."id", "thing_thing"."foo", "thing_thing"."bar"
FROM "thing_thing" WHERE "thing_thing"."foo" LIKE %bar% ESCAPE '\'
Exception thrown: near "ESCAPE": syntax error
SELECT "thing_thing"."id", "thing_thing"."foo", "thing_thing"."bar"
FROM "thing_thing" WHERE "thing_thing"."foo" LIKE ESCAPE '\'
"thing_thing"."bar"
}}}
and the following with MySQL:
{{{
SELECT `thing_thing`.`id`, `thing_thing`.`foo`, `thing_thing`.`bar`
FROM `thing_thing` WHERE `thing_thing`.`foo` = bar
SELECT `thing_thing`.`id`, `thing_thing`.`foo`, `thing_thing`.`bar`
FROM `thing_thing` WHERE `thing_thing`.`foo` = `thing_thing`.`bar`
SELECT `thing_thing`.`id`, `thing_thing`.`foo`, `thing_thing`.`bar`
FROM `thing_thing` WHERE `thing_thing`.`foo` LIKE BINARY %bar%
SELECT `thing_thing`.`id`, `thing_thing`.`foo`, `thing_thing`.`bar`
FROM `thing_thing` WHERE `thing_thing`.`foo` LIKE BINARY
`thing_thing`.`bar`
}}}
So the sqlite3 appears to generate bad SQL, and the MySQL doesn't add the
"%" (presumably it would have to use string concatenation), and so just
does the equivalent of an exact, not a contain. Hope that's helpful.
--
Ticket URL: <http://code.djangoproject.com/ticket/12545>
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