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.
The introduction of the Expression.empty_aggregate_value interface
allows the compilation stage to enable the EmptyResultSet optimization
if all the aggregates expressions implement it.
This also removes unnecessary RegrCount/Count.convert_value() methods.
Disabling the empty result set aggregation optimization when it wasn't
appropriate prevented None returned for a Count aggregation value.
Thanks Nick Pope for the review.
In Query.join() the argument reuse_with_filtered_relation was used to
determine whether to use == or .equals(). As this area of code is
related to aliases, we only expect an instance of Join or BaseTable to
be provided - the only two classes that provide .equals().
In both cases, the implementations of __eq__() and equals() are based
on use of the "identity" property. __eq__() performs an isinstance()
check first, returning NotImplemented if required. BaseTable.equals()
then does a straightforward equality check on "identity". Join.equals()
is a little bit different as it skips checking the last element of the
"identity" property: filtered_relation. This was only included
previously when the with_filtered_relation argument was True, impossible
since bbf141bcdc.
Subquery deconstruction support required implementing complex and
expensive equality rules for sql.Query objects for little benefit as
the latter cannot themselves be made deconstructible to their reference
to model classes.
Making Expression @deconstructible and not BaseExpression allows
interested parties to conform to the "expression" API even if they are
not deconstructible as it's only a requirement for expressions allowed
in Model fields and meta options (e.g. constraints, indexes).
Thanks Phillip Cutter for the report.
This also fixes a performance regression in bbf141bcdc.
This issue started manifesting itself when nesting a combined subquery
relying on exclude() since 8593e162c9 but
sql.Query.combine never properly handled subqueries outer refs in the
first place, see QuerySetBitwiseOperationTests.test_subquery_aliases()
(refs #27149).
Thanks Raffaele Salmaso for the report.
Regression was introduced by fff5186 but was due a long standing issue.
AggregateQuery was abusing Query.subquery: bool by stashing its
compiled inner query's SQL for later use in its compiler which made
select_format checks for Query.subquery wrongly assume the provide
query was a subquery.
This patch prevents that from happening by using a dedicated
inner_query attribute which is compiled at a later time by
SQLAggregateCompiler.
Moving the inner query's compilation to SQLAggregateCompiler.compile
had the side effect of addressing a long standing issue with
aggregation subquery pushdown which prevented converters from being
run. This is now fixed as the aggregation_regress adjustments
demonstrate.
Refs #25367.
Thanks Eran Keydar for the report.
As mentioned in the pre-existing split_exclude() docstring EXISTS is
easier to optimize for query planers and circumvents the IN (NULL)
handling issue.
The latter is already optimized to limit the number of results, avoid
selecting unnecessary fields, and drop ordering if possible without
altering the semantic of the query.
QuerySet.alias() allows creating reusable aliases for expressions that
don't need to be selected but are used for filtering, ordering, or as
a part of complex expressions.
Thanks Simon Charette for reviews.
691def10a0 made all Subquery() instances
equal to each other which broke aggregation subquery pushdown which
relied on object equality to determine which alias it should select.
Subquery.__eq__() will be fixed in an another commit but
Query.rewrite_cols() should haved used object identity from the start.
Refs #30727, #30188.
Thanks Makina Corpus for the report.
Subquery annotation references must be resolved if they are excluded
from the GROUP BY clause by a following .values() call.
Regression in fb3f034f1c.
Thanks Makina Corpus for the report.
Now that order_by() has expression support passing RawSQL() can achieve
the same result.
This was also already supported through QuerySet.extra(order_by) for
years but this API is more or less deprecated at this point.
Clearing the SELECT clause in Query.has_results was orphaning GROUP BY
references to it.
Thanks Thierry Bastian for the report and Baptiste Mispelon for the
bisect.
Regression in fb3f034f1c.
David Wobrock
Keryn Knight
Adam Johnson
Nick Pope
Daniyal
Ian Foote
Simon Charette
Hannes Ljungberg
Mariusz Felisiak
Alexander Lyabah
Christian Klus
Alexandr Tatarinov
matt ferrante
Jacob Walls
Nicolas Baccelli
Manuel Weitzman
Hasan Ramezani