Fixed typos spotted by Claude Paroz
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@ -88,7 +88,7 @@ application where we want to make use of the ``abs()`` operator.
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We have an ``Experiment`` model which records a start value, end value and the
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change (start - end). We would like to find all experiments where the change
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was equal to a certain amount (``Experiment.objects.filter(change__abs=27)``),
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or where it did not exceede a certain amount
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or where it did not exceed a certain amount
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(``Experiment.objects.filter(change__abs__lt=27)``).
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.. note::
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@ -113,7 +113,7 @@ Next, lets register it for ``IntegerField``::
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from django.db.models import IntegerField
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IntegerField.register_lookup(AbsoluteValue)
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We can now run the queris we had before.
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We can now run the queries we had before.
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``Experiment.objects.filter(change__abs=27)`` will generate the following SQL::
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SELECT ... WHERE ABS("experiments"."change") = 27
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@ -184,13 +184,13 @@ transformations in Python.
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.. note::
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In fact, most lookups with ``__abs`` could be implemented as range queries
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like this, and on most database backend it is likely to be more sensible to
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like this, and on most database backends it is likely to be more sensible to
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do so as you can make use of the indexes. However with PostgreSQL you may
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want to add an index on ``abs(change)`` which would allow these queries to
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be very efficient.
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Writing alternative implemenatations for existing lookups
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Writing alternative implementations for existing lookups
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Sometimes different database vendors require different SQL for the same
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operation. For this example we will rewrite a custom implementation for
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@ -210,7 +210,7 @@ We can change the behaviour on a specific backend by creating a subclass of
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Field.register_lookup(MySQLNotExact)
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We can then register it with ``Field``. It takes the place of the original
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``NotEqual`` class as it has
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``NotEqual`` class as it has the same ``lookup_name``.
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When compiling a query, Django first looks for ``as_%s % connection.vendor``
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methods, and then falls back to ``as_sql``. The vendor names for the in-built
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@ -189,7 +189,7 @@ Custom lookups work just like Django's inbuilt lookups (e.g. ``lte``,
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The :class:`django.db.models.Lookup` class provides a way to add lookup
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operators for model fields. As an example it is possible to add ``day_lte``
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opertor for ``DateFields``.
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operator for ``DateFields``.
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The :class:`django.db.models.Transform` class allows transformations of
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database values prior to the final lookup. For example it is possible to
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