mirror of
https://github.com/sqlalchemy/sqlalchemy.git
synced 2026-05-31 04:48:02 -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.
80 lines
3.0 KiB
Python
80 lines
3.0 KiB
Python
"""advanced.py
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Illustrate usage of Query combined with the FromCache option,
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including front-end loading, cache invalidation, namespace techniques
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and collection caching.
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"""
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from environment import Session
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from model import Person, Address, cache_address_bits
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from caching_query import FromCache, RelationshipCache
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from sqlalchemy.orm import joinedload
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def load_name_range(start, end, invalidate=False):
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"""Load Person objects on a range of names.
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start/end are integers, range is then
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"person <start>" - "person <end>".
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The cache option we set up is called "name_range", indicating
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a range of names for the Person class.
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The `Person.addresses` collections are also cached. Its basically
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another level of tuning here, as that particular cache option
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can be transparently replaced with joinedload(Person.addresses).
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The effect is that each Person and his/her Address collection
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is cached either together or separately, affecting the kind of
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SQL that emits for unloaded Person objects as well as the distribution
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of data within the cache.
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"""
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q = Session.query(Person).\
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filter(Person.name.between("person %.2d" % start, "person %.2d" % end)).\
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options(cache_address_bits).\
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options(FromCache("default", "name_range"))
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# have the "addresses" collection cached separately
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# each lazyload of Person.addresses loads from cache.
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q = q.options(RelationshipCache("default", "by_person", Person.addresses))
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# alternatively, eagerly load the "addresses" collection, so that they'd
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# be cached together. This issues a bigger SQL statement and caches
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# a single, larger value in the cache per person rather than two
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# separate ones.
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#q = q.options(joinedload(Person.addresses))
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# if requested, invalidate the cache on current criterion.
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if invalidate:
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q.invalidate()
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return q.all()
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print "two through twelve, possibly from cache:\n"
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print ", ".join([p.name for p in load_name_range(2, 12)])
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print "\ntwenty five through forty, possibly from cache:\n"
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print ", ".join([p.name for p in load_name_range(25, 40)])
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# loading them again, no SQL is emitted
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print "\ntwo through twelve, from the cache:\n"
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print ", ".join([p.name for p in load_name_range(2, 12)])
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# but with invalidate, they are
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print "\ntwenty five through forty, invalidate first:\n"
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print ", ".join([p.name for p in load_name_range(25, 40, True)])
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# illustrate the address loading from either cache/already
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# on the Person
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print "\n\nPeople plus addresses, two through twelve, addresses possibly from cache"
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for p in load_name_range(2, 12):
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print p.format_full()
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# illustrate the address loading from either cache/already
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# on the Person
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print "\n\nPeople plus addresses, two through twelve, addresses from cache"
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for p in load_name_range(2, 12):
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print p.format_full()
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print "\n\nIf this was the first run of advanced.py, try "\
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"a second run. Only one SQL statement will be emitted."
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