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Fixed #21478 -- Corrected docs for when Field.db_type() is called.

This commit is contained in:
Anubhav Joshi 2013-12-19 03:01:48 +05:30
parent e2f142030b
commit 1a9f13df59
1 changed files with 7 additions and 4 deletions
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11
docs/howto/custom-model-fields.txt
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@ -458,11 +458,14 @@ For example::
else:
return 'timestamp'
The :meth:`.db_type` method is only called by Django when the framework
The :meth:`.db_type` method is called by Django when the framework
constructs the ``CREATE TABLE`` statements for your application -- that is,
when you first create your tables. It's not called at any other time, so it can
afford to execute slightly complex code, such as the
``connection.settings_dict`` check in the above example.
when you first create your tables. It is also called when constructing a
``WHERE`` clause that includes the model field -- that is, when you retrieve data
using QuerySet methods like ``get()``, ``filter()``, and ``exclude()`` and have
the model field as an argument. It's not called at any other time, so it can afford to
execute slightly complex code, such as the ``connection.settings_dict`` check in
the above example.
Some database column types accept parameters, such as ``CHAR(25)``, where the
parameter ``25`` represents the maximum column length. In cases like these,