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| author | Keryn Knight <keryn@kerynknight.com> | 2021-08-14 15:30:54 +0100 |
|---|---|---|
| committer | Mariusz Felisiak <felisiak.mariusz@gmail.com> | 2021-08-19 13:28:59 +0200 |
| commit | bf5abf1bdcedb15e949db419c61eeec7c88414ea (patch) | |
| tree | ad3354a181a6a2d8cb75cab7e9dc4087ce72990f /django/db/models/sql/query.py | |
| parent | faf6d48590386987a08178ca0d7154b1500560b8 (diff) | |
Fixed #33025 -- Avoided accessing the database connections in Query.build_lookup() when not necessary.
Of the built-in backends, only Oracle treats empty strings and nulls as
equal, so avoid testing the default connection backend for
interprets_empty_strings_as_nulls if it can be established from the
lookup that it wouldn't affect the lookup instance returned. This
improves performance a small amount for most lookups being built,
because accessing the connections requires touching the thread critical
`Local` which is an expensive operation.
Diffstat (limited to 'django/db/models/sql/query.py')
| -rw-r--r-- | django/db/models/sql/query.py | 7 |
1 files changed, 5 insertions, 2 deletions
diff --git a/django/db/models/sql/query.py b/django/db/models/sql/query.py index 181d4419fa..1258eb61a9 100644 --- a/django/db/models/sql/query.py +++ b/django/db/models/sql/query.py @@ -1192,8 +1192,11 @@ class Query(BaseExpression): # stage because join promotion can't be done in the compiler. Using # DEFAULT_DB_ALIAS isn't nice but it's the best that can be done here. # A similar thing is done in is_nullable(), too. - if (connections[DEFAULT_DB_ALIAS].features.interprets_empty_strings_as_nulls and - lookup_name == 'exact' and lookup.rhs == ''): + if ( + lookup_name == 'exact' and + lookup.rhs == '' and + connections[DEFAULT_DB_ALIAS].features.interprets_empty_strings_as_nulls + ): return lhs.get_lookup('isnull')(lhs, True) return lookup |