Refactored compiler SELECT, GROUP BY and ORDER BY generation.
While there, also refactored select_related() implementation
(get_cached_row() and get_klass_info() are now gone!).
Made get_db_converters() method work on expressions instead of
internal_type. This allows the backend converters to target
specific expressions if need be.
Added query.context, this can be used to set per-query state.
Also changed the signature of database converters. They now accept
context as an argument.
The .dates() queries were implemented by using custom Query, QuerySet,
and Compiler classes. Instead implement them by using expressions and
database converters APIs.
This also defines QuerySet.__bool__ for consistency though this should not have any consequence as bool(qs) used to fallback on QuerySet.__len__ in Py3.
Complete rework of translating data values from database
Deprecation of SubfieldBase, removal of resolve_columns and
convert_values in favour of a more general converter based approach and
public API Field.from_db_value(). Now works seamlessly with aggregation,
.values() and raw queries.
Thanks to akaariai in particular for extensive advice and inspiration,
also to shaib, manfre and timograham for their reviews.
The Model.from_db() is intended to be used in cases where customization
of model loading is needed. Reasons can be performance, or adding custom
behavior to the model (for example "dirty field tracking" to issue
automatic update_fields when saving models).
A big thank you to Tim Graham for the review!
Regression from f51c1f59 when using select_related then prefetch_related
on the reverse side of an O2O:
Author.objects.select_related('bio').prefetch_related('bio__books')
Thanks Aymeric Augustin for the report and tests. Refs #17001.
Previously, known related objects overwrote related objects loaded
though select_related. This could cancel the effect of select_related
when it was used over more than one level.
Thanks boxm for the bug report and timo for bisecting the regression.
So as the save step is centralized in create(), especially useful
when customizing behavior in subclasses.
Thanks craig.labenz@gmail.com for the report.
The original patch for custom prefetches didn't allow usage of custom
queryset for single valued relations (along ForeignKey or OneToOneKey).
Allowing these enables calling performance oriented queryset methods like
select_related or defer/only.
Thanks @akaariai and @timgraham for the reviews. Refs #17001.
Previously, doing so resulted in invalid data or crash.
Thanks jtiai for the report and Karol Jochelson,
Jakub Nowak, Loic Bistuer, and Baptiste Mispelon for reviews.
This commit touchs various parts of the code base and test framework. Any
found usage of opening a cursor for the sake of initializing a connection
has been replaced with 'ensure_connection()'.
Updated SQLUpdateCompiler.execute_sql to match the behavior described in
the docstring; the 'first non-empty query' will now include all queries,
not just the main and first related update.
Added CURSOR and NO_RESULTS result_type constants to make the usages more
self documenting and allow execute_sql to explicitly close the cursor when
it is no longer needed.
This patch introduces the Prefetch object which allows customizing prefetch
operations.
This enables things like filtering prefetched relations, calling select_related
from a prefetched relation, or prefetching the same relation multiple times
with different querysets.
When a Prefetch instance specifies a to_attr argument, the result is stored
in a list rather than a QuerySet. This has the fortunate consequence of being
significantly faster. The preformance improvement is due to the fact that we
save the costly creation of a QuerySet instance.
Thanks @akaariai for the original patch and @bmispelon and @timgraham
for the reviews.
Loic Bistuer
Anssi Kääriäinen
Daniel Pyrathon
Markus Holtermann
Jon Dufresne
Josh Smeaton
Gabe Jackson
Thomas Chaumeny
Claude Paroz
Artem Rizhov
Marc Tamlyn
Akis Kesoglou
Andrew Torpedov
Tim Graham
Shai Berger
Anubhav Joshi
Alex Gaynor
Aymeric Augustin
Loic Bistuer
Rodolfo Carvalho
Artur Frysiak
Albert Wang
Michael Manfre
Roger Hu
Christopher Medrela
coagulant
Alasdair Nicol