#31275: Optimize MariaDB/MySQL sql_flush
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Reporter: Adam | Owner: nobody
(Chainz) Johnson |
Type: | Status: new
Cleanup/optimization |
Component: Database | Version: master
layer (models, ORM) |
Severity: Normal | Keywords:
Triage Stage: | Has patch: 0
Unreviewed |
Needs documentation: 0 | Needs tests: 0
Patch needs improvement: 0 | Easy pickings: 0
UI/UX: 0 |
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This was suggested as an extra feature for Django-MySQL by @jonatron in
https://github.com/adamchainz/django-mysql/pull/611/files , but it would
make more sense to make it in Django core.
Currently MySQL's sql_flush emits TRUNCATE TABLE statements. These are
relatively slow on small tables since they force recreation of the table
on disk. The alternative, `DELETE FROM`, is faster. I can see a diference
even for a single empty table locally (MariaDB 10.4):
{{{
chainz@localhost [21]> truncate t2;
Query OK, 0 rows affected (0.005 sec)
chainz@localhost [22]> delete from t2;
Query OK, 0 rows affected (0.000 sec)
}}}
`TransactionTestCase` uses sql_flush, via the flush management command, to
reset the database. Most test suites don't use very large tables, so
using `DELETE FROM` should normally be faster in this case. Optimizing it
MySQL to use `DELETE FROM` for flushing, at least for tables up to a
certain size (1000 rows or similar heuristic) could save lot of time when
using `TransactionTestCase`.
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Ticket URL: <https://code.djangoproject.com/ticket/31275>
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