#12192: Don't execute sql query with limit 0
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Reporter: Suor | Owner: ramiro
Status: new | Milestone:
Component: Database layer (models, ORM) | Version: 1.1
Resolution: | Keywords:
Stage: Design decision needed | Has_patch: 1
Needs_docs: 0 | Needs_tests: 0
Needs_better_patch: 0 |
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Changes (by ramiro):
* needs_better_patch: => 0
* needs_tests: => 0
* owner: nobody => ramiro
* needs_docs: => 0
* has_patch: 0 => 1
* stage: Unreviewed => Design decision needed
Comment:
I've attached two patches that implement detection of the `high_mark ==
low_mark` condition and avoid going to the DB with such a query, the
second patch could be even slightly more efficient because it shortcuts
execution of `Query.as_sql()` early completely avoiding the setup and
generation of the SQL query text.
One thing to review and decide is that isn't clear from the docstrings
and comments what `Query.as_sql()` is supposed to return to signal no SQL
query text was generated. The patches currently return an empty string but
I don't know now if it should be None.
Tests that exercise this already exist in `modeltests/basic` and
`regressiontests/queries`.
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Ticket URL: <http://code.djangoproject.com/ticket/12192#comment:1>
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