OK, thank a lot !
Le jeudi 13 juillet 2017 06:01:45 UTC+3, Mike Bayer a écrit :
>
> this is how that would have to be mapped, hypothetically:
>
> class EngineerBase(Person):
> __tablename__ = 'engineer'
>
> id = Column(ForeignKey('person.id'), primary_key=True)
> engineer_name = Column(String(30))
>
> __mapper_args__ = {
> 'polymorphic_load': 'selectin'
> }
>
>
> class EngineerType1(EngineerBase):
> __mapper_args__ = {
> 'polymorphic_identity': 'engineer_t1',
> 'polymorphic_load': 'inline'
> }
>
>
> class EngineerType2(EngineerBase):
> __mapper_args__ = {
> 'polymorphic_identity': 'engineer_t2',
> 'polymorphic_load': 'inline'
> }
>
>
> doesn't work of course since the polymorphic selectin load is a new
> feature trying to work its way into a very intricate workflow. I
> threw up
> https://bitbucket.org/zzzeek/sqlalchemy/issues/4026/mixing-selectin-load-on-top-of-inline
>
> to look into it. not sure how easy / hard it would be.
>
> On Wed, Jul 12, 2017 at 7:09 PM, <yoch....@gmail.com <javascript:>>
> wrote:
> > Here a MCWE :
> >
> > from sqlalchemy import Table, Column, Integer, String, ForeignKey,
> > create_engine
> > from sqlalchemy.orm import Session
> > from sqlalchemy.ext.declarative import declarative_base
> >
> >
> > Base = declarative_base()
> >
> >
> > class Person(Base):
> > __tablename__ = 'person'
> >
> > id = Column(Integer, primary_key=True)
> > type = Column(String(50), nullable=False)
> > name = Column(String(50))
> >
> > __mapper_args__ = {
> > 'polymorphic_identity': 'person',
> > 'polymorphic_on': type
> > }
> >
> >
> > class Manager(Person):
> > __tablename__ = 'manager'
> >
> > id = Column(ForeignKey('person.id'), primary_key=True)
> > manager_name = Column(String(30))
> >
> > __mapper_args__ = {
> > 'polymorphic_identity': 'manager',
> > 'polymorphic_load': 'selectin'
> > }
> >
> >
> > class EngineerBase(Person):
> > __tablename__ = 'engineer'
> >
> > id = Column(ForeignKey('person.id'), primary_key=True)
> > engineer_name = Column(String(30))
> >
> >
> > class EngineerType1(EngineerBase):
> > __mapper_args__ = {
> > 'polymorphic_identity': 'engineer_t1',
> > 'polymorphic_load': 'selectin'
> > }
> >
> >
> > class EngineerType2(EngineerBase):
> > __mapper_args__ = {
> > 'polymorphic_identity': 'engineer_t2',
> > 'polymorphic_load': 'selectin'
> > }
> >
> >
> > engine = create_engine('sqlite://')
> > Base.metadata.create_all(engine)
> >
> > engine.echo = True
> >
> > session = Session(engine)
> >
> > eng1 = EngineerType1()
> > eng2 = EngineerType2()
> >
> > session.add_all([eng1, eng2])
> > session.commit()
> >
> > session.query(Person).all()
> >
> > produces the following three queries :
> >
> > 2017-07-13 00:59:07,243 INFO sqlalchemy.engine.base.Engine SELECT
> person.id
> > AS person_id, person.type AS person_type, person.name AS person_name
> > FROM person
> > 2017-07-13 00:59:07,243 INFO sqlalchemy.engine.base.Engine ()
> > 2017-07-13 00:59:07,248 INFO sqlalchemy.engine.base.Engine SELECT
> > engineer.id AS engineer_id, person.id AS person_id, person.type AS
> > person_type
> > FROM person JOIN engineer ON person.id = engineer.id
> > WHERE person.id IN (?) AND person.type IN (?) ORDER BY person.id
> > 2017-07-13 00:59:07,249 INFO sqlalchemy.engine.base.Engine (2,
> > 'engineer_t2')
> > 2017-07-13 00:59:07,253 INFO sqlalchemy.engine.base.Engine SELECT
> > engineer.id AS engineer_id, person.id AS person_id, person.type AS
> > person_type
> > FROM person JOIN engineer ON person.id = engineer.id
> > WHERE person.id IN (?) AND person.type IN (?) ORDER BY person.id
> > 2017-07-13 00:59:07,254 INFO sqlalchemy.engine.base.Engine (1,
> > 'engineer_t1')
> >
> > The last two queries can be grouped together.
> >
> > Le jeudi 13 juillet 2017 01:45:46 UTC+3, yoch....@gmail.com a écrit :
> >>
> >> I have a mixed configuration with both joined and single table
> subclasses
> >> in a two-levels inheritance (like that), so selectin seems to be the
> right
> >> choice for me.
> >>
> >> Le jeudi 13 juillet 2017 01:09:50 UTC+3, Mike Bayer a écrit :
> >>>
> >>> On Wed, Jul 12, 2017 at 4:54 PM, <yoch....@gmail.com> wrote:
> >>> > I noticed that {'polymorphic_load': 'selectin'} on single table
> >>> > inheritance
> >>> > can make several SQL queries unnecessarily.
> >>>
> >>> well "selectin" loading would be inappropriate for single table
> >>> inheritance because you are telling it to emit additional queries for
> >>> additional subclasses, when in reality you'd like the original query
> >>> just to include all columns. For this reason the traditional
> >>> "with_polymorphic" approach is more appropriate for eager loading of
> >>> single table subclasses.
> >>>
> >>>
> >>> >
> >>> >
> >>> > 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
> >>> >
> >>> > --
> >>> > SQLAlchemy -
> >>> > The Python SQL Toolkit and Object Relational Mapper
> >>> >
> >>> > http://www.sqlalchemy.org/
> >>> >
> >>> > To post example code, please provide an MCVE: Minimal, Complete, and
> >>> > Verifiable Example. See http://stackoverflow.com/help/mcve for a
> full
> >>> > description.
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> >
> > --
> > SQLAlchemy -
> > The Python SQL Toolkit and Object Relational Mapper
> >
> > http://www.sqlalchemy.org/
> >
> > To post example code, please provide an MCVE: Minimal, Complete, and
> > Verifiable Example. See http://stackoverflow.com/help/mcve for a full
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--
SQLAlchemy -
The Python SQL Toolkit and Object Relational Mapper
http://www.sqlalchemy.org/
To post example code, please provide an MCVE: Minimal, Complete, and Verifiable
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