I noticed that {'polymorphic_load': 'selectin'} on single table inheritance
can make several SQL queries unnecessarily.
Le mercredi 12 juillet 2017 22:02:04 UTC+3, yoch....@gmail.com a écrit :
>
> Very awaited version for me (because the selectin) !
>
> I tested in my code both the eagerload and the polymorphic usages, and
> everything works perfectly.
>
> Thank you Mike
>
> Le lundi 10 juillet 2017 16:44:03 UTC+3, Mike Bayer a écrit :
>>
>> SQLAlchemy release 1.2.0b1 is now available.
>>
>> This is the first beta for the 1.2 series of SQLAlchemy. As is always
>> the case for beta releases, the release is available on Pypi, but only
>> installable when specifying the --pre flag with pip.
>>
>> Key highlights of version 1.2 include:
>>
>> * Connection pool pre-ping - The connection pool now includes an
>> optional "pre ping" feature that will test the "liveness" of a pooled
>> connection for every connection checkout, transparently recycling the
>> DBAPI connection if the database is disconnected. This feature
>> eliminates the need for the "pool recycle" flag as well as the issue
>> of errors raised when a pooled connection is used after a database
>> restart.
>>
>> * New eagerloading features - an all-new eager loader called
>> "selectin" is added. This loader is similar to "subquery" eager
>> loading, but foregoes embedding a complex subquery in favor of using a
>> simple IN expression which uses the primary key values of the
>> just-loaded objects to locate related rows. This style of loading will
>> perform dramatically better than "subquery" eager loading in many
>> cases.
>>
>> * New polymorphic loading options - A new "selectin" loader is also
>> implemented for polymorphic inheritance hierarchies, which will load
>> the extra table rows for subclasses in a result set all at once,
>> without the need to use JOIN or "with_polymorphic". New declarative
>> options are added to allow per-subclass polymorphic loading
>> configuration as well.
>>
>> * The IN operator now emits a simple expression for empty IN - The
>> long standing behavior of "empty in" resolving to a non-performant
>> expression with a warning has been removed as default behavior; for an
>> IN with no elements, a simple 1 != 1 expression is now used to
>> evaluate to "false".
>>
>> * INSERT..ON DUPLICATE KEY UPDATE support in MySQL - complementing the
>> support for PostgreSQL "INSERT..ON CONFLICT" in 1.1, the MySQL dialect
>> now supports the ON DUPLICATE KEY phrase. Simple database-agnostic
>> "merge" routines can now be composed against these two backends.
>>
>> * COMMENT Support - thanks to a generous contribution, version 1.2 can
>> emit all necessary DDL as well as fully reflect SQL comments for
>> tables and columns against the MySQL, PostgreSQL, and Oracle backends.
>>
>> * SQL expression caching within ORM loaders - the "lazyload" feature
>> as well as the new "selectin" loading now use SQL expression caching
>> using the "baked query" extension when emitting queries, removing a
>> significant bulk of Python overhead from these very common operations.
>>
>> Users should carefully review the "What's New in SQLAlchemy 1.2?
>> document" [1] as well as the Changelog [2] to note which behaviors and
>> issues are affected. We'd like to thank the many contributors who
>> helped with this release.
>>
>> SQLAlchemy 1.2.0b1 is available on the Download Page [3].
>>
>> [1] http://docs.sqlalchemy.org/en/latest/changelog/migration_12.html
>> [2] http://www.sqlalchemy.org/changelog/CHANGES_1_2_0b1
>> [3] http://www.sqlalchemy.org/download.html
>>
>
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