1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
|
"""Illustrate how to load some data, and cache the results.
"""
from sqlalchemy import select
from .caching_query import FromCache
from .environment import cache
from .environment import Session
from .model import Person
# load Person objects. cache the result in the "default" cache region
print("loading people....")
people = Session.scalars(select(Person).options(FromCache("default"))).all()
# remove the Session. next query starts from scratch.
Session.remove()
# load again, using the same FromCache option. now they're cached,
# so no SQL is emitted.
print("loading people....again!")
people = Session.scalars(select(Person).options(FromCache("default"))).all()
# Specifying a different query produces a different cache key, so
# these results are independently cached.
print("loading people two through twelve")
people_two_through_twelve = Session.scalars(
select(Person)
.options(FromCache("default"))
.filter(Person.name.between("person 02", "person 12"))
).all()
# the data is cached under string structure of the SQL statement, *plus*
# the bind parameters of the query. So this query, having
# different literal parameters under "Person.name.between()" than the
# previous one, issues new SQL...
print("loading people five through fifteen")
people_five_through_fifteen = Session.scalars(
select(Person)
.options(FromCache("default"))
.filter(Person.name.between("person 05", "person 15"))
).all()
# ... but using the same params as are already cached, no SQL
print("loading people two through twelve...again!")
people_two_through_twelve = Session.scalars(
select(Person)
.options(FromCache("default"))
.filter(Person.name.between("person 02", "person 12"))
).all()
# invalidate the cache for the three queries we've done. Recreate
# each Query, which includes at the very least the same FromCache,
# same list of objects to be loaded, and the same parameters in the
# same order, then call invalidate().
print("invalidating everything")
cache.invalidate(Session.query(Person), {}, FromCache("default"))
cache.invalidate(
select(Person).filter(Person.name.between("person 02", "person 12")),
{},
FromCache("default"),
)
cache.invalidate(
select(Person).filter(Person.name.between("person 05", "person 15")),
{},
FromCache("default", "people_on_range"),
)
|
