#10358: manage.py sqlall is not truncating long table names for ManyToManyField
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Reporter: jb0t | Owner: jacob
Status: closed | Milestone: 1.1
Component: Documentation | Version: 1.0
Resolution: fixed | Keywords:
Stage: Accepted | Has_patch: 1
Needs_docs: 0 | Needs_tests: 0
Needs_better_patch: 0 |
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Comment (by ramiro):
Actually, the note added to the docs is incorrect, as it was the content
it replaced.
Django doesn't set a hard limit of 64 nor 32 characters on the names of
the auto-generated m2m intermediary tables, is simply uses the max
identifier length (provided by a `DatabaseOperations.max_name_length()`
method) reported by the backend, if any.
The Django MySQL DB backend doesn't define `max_name_length()` and because
of that the ORM machinery doesn't truncate the m2m table name at all. I
suspect what the OP was seeing is MySQL showing its 64 chars limitation (a
comment in the Django source seems to indicate that MySQL doesn't have a
hard limit on the length of identifiers, but rather it only considers the
first 64 chars to discern among them, I couldn't confirm this).
In contrast, in the Oracle case the RDBMS identifier hard limit is 30,
this is correctly reported by the Django DB backend and so an identifier
of length > 30 will get converted to a 30 char identifier composed of the
original 26 first chars plus 4 chars of and MD5 hash.
Because of the above, IMHO the current note lacks generality and is a bit
misleading even in the case of MySQL.
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Ticket URL: <http://code.djangoproject.com/ticket/10358#comment:7>
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