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https://github.com/sqlalchemy/sqlalchemy.git
synced 2026-05-31 21:08:36 -04:00
Mike Bayer
5ab558004c
such that the Session, cache manager, declarative_base are part of environment, and custom cache code is portable and now within "caching_query.py". This allows the example to be easier to "drop in" to existing projects.
63 lines
2.6 KiB
Python
63 lines
2.6 KiB
Python
"""helloworld.py
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Illustrate how to load some data, and cache the results.
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"""
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from environment import Session
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from model import Person
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from caching_query import FromCache
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# load Person objects. cache the result under the namespace "all_people".
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print "loading people...."
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people = Session.query(Person).options(FromCache("default", "all_people")).all()
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# remove the Session. next query starts from scratch.
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Session.remove()
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# load again, using the same FromCache option. now they're cached
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# under "all_people", no SQL is emitted.
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print "loading people....again!"
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people = Session.query(Person).options(FromCache("default", "all_people")).all()
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# want to load on some different kind of query ? change the namespace
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# you send to FromCache
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print "loading people two through twelve"
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people_two_through_twelve = Session.query(Person).\
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options(FromCache("default", "people_on_range")).\
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filter(Person.name.between("person 02", "person 12")).\
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all()
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# the data is cached under the "namespace" you send to FromCache, *plus*
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# the bind parameters of the query. So this query, having
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# different literal parameters under "Person.name.between()" than the
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# previous one, issues new SQL...
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print "loading people five through fifteen"
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people_five_through_fifteen = Session.query(Person).\
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options(FromCache("default", "people_on_range")).\
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filter(Person.name.between("person 05", "person 15")).\
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all()
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# ... but using the same params as are already cached, no SQL
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print "loading people two through twelve...again!"
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people_two_through_twelve = Session.query(Person).\
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options(FromCache("default", "people_on_range")).\
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filter(Person.name.between("person 02", "person 12")).\
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all()
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# invalidate the cache for the three queries we've done. Recreate
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# each Query, which includes at the very least the same FromCache,
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# same list of objects to be loaded, and the same parameters in the
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# same order, then call invalidate().
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print "invalidating everything"
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Session.query(Person).options(FromCache("default", "all_people")).invalidate()
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Session.query(Person).\
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options(FromCache("default", "people_on_range")).\
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filter(Person.name.between("person 02", "person 12")).invalidate()
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Session.query(Person).\
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options(FromCache("default", "people_on_range")).\
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filter(Person.name.between("person 05", "person 15")).invalidate()
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