#22309: error accessing django.db.connection.features?
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Reporter: lucastan@… | Owner: nobody
Type: Uncategorized | Status: closed
Component: Database layer | Version: 1.6
(models, ORM) | Resolution: needsinfo
Severity: Normal | Triage Stage:
Keywords: | Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
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Comment (by akaariai):
We should use temporary tables. They are connection local, and in any case
using temporary table is a lot better than using normal tables. Temporary
tables are supported from MySQL 3.23 onwards, so See
http://dev.mysql.com/doc/refman/4.1/en/create-table.html. The only
question is if temporary tables have different transaction rules than
normal tables. I don't see anything indicating that this is the case, but
then again when dealing with MySQL it wouldn't be a surprise if this is
the case.
So, needed here:
1) check that temp tables work like normal tables when it comes to
transaction management. My understanding is that the default engine in use
for MySQL affects if transactions are usable, so the check would be to
switch to using MyISAM tables as default and then verify that temp table
gives the same result as normal tables.
2) create temp table doesn't commit the current transaction - create
table does. This might change the behavior of the method.
3) check that this doesn't affect other backends (sqlite seems to use
the supports_transactions method, too)
4) write a patch
Also, the supports_transactions method seems scary. If ran inside
transaction the end result is silent rollback + switch to autocommit mode.
So, step 5) is to verify when exactly this method is ran, and also make
the method assert that no transaction is open when it is ran. If it is
possible that this method will get ran inside transaction and when not
testing then we should likely backpatch the fix, too, as this is a clear
data loss issue in that case.
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Ticket URL: <https://code.djangoproject.com/ticket/22309#comment:5>
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