mirror of
https://github.com/sqlalchemy/sqlalchemy.git
synced 2026-05-09 18:30:39 -04:00
Mike Bayer
79 lines
2.7 KiB
Python
79 lines
2.7 KiB
Python
"""
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Illustrates how to embed Beaker cache functionality within
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the Query object, allowing full cache control as well as the
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ability to pull "lazy loaded" attributes from long term cache
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as well.
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In this demo, the following techniques are illustrated:
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* Using custom subclasses of Query
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* Basic technique of circumventing Query to pull from a
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custom cache source instead of the database.
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* Rudimental caching with Beaker, using "regions" which allow
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global control over a fixed set of configurations.
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* Using custom MapperOption objects to configure options on
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a Query, including the ability to invoke the options
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deep within an object graph when lazy loads occur.
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E.g.::
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# query for Person objects, specifying cache
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q = Session.query(Person).options(FromCache("default", "all_people"))
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# specify that each Person's "addresses" collection comes from
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# cache too
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q = q.options(RelationshipCache("default", "by_person", Person.addresses))
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# query
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print q.all()
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To run, both SQLAlchemy and Beaker (1.4 or greater) must be
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installed or on the current PYTHONPATH. The demo will create a local
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directory for datafiles, insert initial data, and run. Running the
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demo a second time will utilize the cache files already present, and
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exactly one SQL statement against two tables will be emitted - the
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displayed result however will utilize dozens of lazyloads that all
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pull from cache.
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The demo scripts themselves, in order of complexity, are run as follows::
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python examples/beaker_caching/helloworld.py
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python examples/beaker_caching/relationship_caching.py
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python examples/beaker_caching/advanced.py
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python examples/beaker_caching/local_session_caching.py
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Listing of files:
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environment.py - Establish the Session, the Beaker cache
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manager, data / cache file paths, and configurations,
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bootstrap fixture data if necessary.
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caching_query.py - Represent functions and classes
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which allow the usage of Beaker caching with SQLAlchemy.
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Introduces a query option called FromCache.
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model.py - The datamodel, which represents Person that has multiple
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Address objects, each with PostalCode, City, Country
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fixture_data.py - creates demo PostalCode, Address, Person objects
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in the database.
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helloworld.py - the basic idea.
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relationship_caching.py - Illustrates how to add cache options on
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relationship endpoints, so that lazyloads load from cache.
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advanced.py - Further examples of how to use FromCache. Combines
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techniques from the first two scripts.
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local_session_caching.py - Grok everything so far ? This example
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creates a new Beaker container that will persist data in a dictionary
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which is local to the current session. remove() the session
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and the cache is gone.
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"""
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