As a QuerySet resolves to Query the outer column references grouping logic
should be defined on the latter and proxied from Subquery for the cases where
get_group_by_cols is called on unresolved expressions.
Thanks Antonio Terceiro for the report and initial patch.
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.
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.
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.
This required implementing a limited form of dynamic dispatch to combine
expressions with numerical output. Refs #26355 should eventually provide
a better interface for that.
Previously unresolved Value() instances were only allowed to be
compiled if they weren't initialized with an output_field.
Given the usage of unresolved Value() instances is relatively common in
as_sql() overrides it's less controversial to add explicit support for
this previously undefined behavior now and revisit whether or not it
should be deprecated in the future.
Both backends order NULLs first on ascending ordering and last on
descending ordering which makes ORDER BY IS (NOT)? NULL wasteful when
asc(nulls_first) and desc(nulls_last) are used since it prevents indice
usage.
This prevent having to pass simple_col through multiple function calls
by defining whether or not references should be resolved with aliases
at the Query level.
MySQL & MariaDB support the standard IS NULL and IS NOT NULL so
the same workaround used for NULLS FIRST and NULLS LAST that is
used for SQLite < 3.30.0 can be used.
Thanks Simon Charette for the discussion.
Simon Charette
Matthijs Kooijman
Adam Johnson
David Wobrock
Ian Foote
Mariusz Felisiak
Tobias Bengfort
David Beitey
Hasan Ramezani
Hannes Ljungberg
Hannes Ljungberg
Nick Pope
Simon Charette
Sergey Fedoseev
Thodoris Sotiropoulos
Ryan Heard
Rohit
Simon Charette