diff options
Diffstat (limited to 'docs')
| -rw-r--r-- | docs/topics/db/optimization.txt | 10 |
1 files changed, 4 insertions, 6 deletions
diff --git a/docs/topics/db/optimization.txt b/docs/topics/db/optimization.txt index 9c4ba314ae..ed990a123f 100644 --- a/docs/topics/db/optimization.txt +++ b/docs/topics/db/optimization.txt @@ -189,12 +189,10 @@ Doing the following is potentially quite slow: First of all, ``headline`` is not indexed, which will make the underlying database fetch slower. -Second, the lookup doesn't guarantee that only one object will be returned. -If the query matches more than one object, it will retrieve and transfer all of -them from the database. This penalty could be substantial if hundreds or -thousands of records are returned. The penalty will be compounded if the -database lives on a separate server, where network overhead and latency also -play a factor. +Second, the lookup may return multiple results. Even though Django applies a +limit of 21 objects when using :meth:`~django.db.models.query.QuerySet.get`, +the database may still need to scan everything to evaluate a non-unique +condition. Narrowing your query up-front is more efficient. Retrieve related objects efficiently ==================================== |