#9349: Support for fixed Char database field
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Reporter: aiev | Owner: nobody
Status: reopened | Milestone:
Component: Database layer (models, ORM) | Version: SVN
Resolution: | Keywords: char,
varchar, fixedcharfield, field
Stage: Unreviewed | Has_patch: 0
Needs_docs: 0 | Needs_tests: 0
Needs_better_patch: 0 |
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Changes (by efloehr):
* cc: efloehr (added)
* keywords: char, varchar => char, varchar, fixedcharfield, field
* status: closed => reopened
* resolution: wontfix =>
* summary: CharField create a varchar column => Support for fixed Char
database field
Comment:
I would like this to be revisited, if possible, as I have seen in a number
of cases where folks have asked for this functionality. I think that the
"very minimal" cases where this is needed are not as small as one might
first think. It is certainly not trivially small (it's appeared a couple
of times on Stack Overflow, for example). The benefits of char fields are
many, and as a first-order field type in all major databases (Postgres,
MySQL, Oracle, etc.), the question should be "Why '''''SHOULDN'T'''''
Django support fixed length character fields?"
Fixed char fields are useful in a number of domains, including character-
based flags (in my domain, quality and measurement flags are often
expressed as single characters). Varchar's in those cases result in non-
trivial disk usage and performance impacts versus char fields. Besides
the obvious ones, Django automagically creates a "like" index in Postgres
for all varchar fields. In my particular application, changing from
Django-autogenerated varchar fields to char fields dropped the size of the
database from 550GB to 300GB. There are many cases when there really is
fixed-length character data that needs stored.
Should you choose to close this issue again, and require folks to have to
create their own field types for first-order database field types, I leave
for those searching for fixed-length character fields in Django code a
hacky work-around:
{{{
class FixedCharField(models.Field):
def __init__(self, max_length, *args, **kwargs):
self.max_length = max_length
super(FixedCharField, self).__init__(max_length=max_length, *args,
**kwargs)
def db_type(self):
return 'char(%s)' % self.max_length
}}}
Just use {{{ FixedCharField }}} where you are currently using {{{
models.CharField }}} and you should be good to go. The max_length
parameter is used to specify the length of the char field.
--
Ticket URL: <http://code.djangoproject.com/ticket/9349#comment:2>
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