A postgresql backed cache system
Project description
DBCACHE
This small library provides small and simple stores based on postgresql for the following purposes:
- a cache store for bytes with an expiration timestamp
- a key-value store with json serializable values
- a versioned key-value store with values as bytes
To initialize the database schema, type:
$ dbcache init-db postgresql://foo:bar@postgresql/mydb
Example usage (cache):
from time import sleep
from datetime import timedelta
from dbcache.api import dbcache
cache = dbcache('postgresql://foo:bar@postgresql/mydb')
assert cache.get('a') is None
cache.set('a', b'aaa')
assert cache.get('a') == b'aaa'
cache.delete('a')
assert cache.get('a') is None
cache.set('b', b'bbb', lifetime=timedelta(seconds=1))
assert cache.get('b') == b'bbb'
sleep(1)
assert cache.get('b') is None
Example usage (key/value store):
from dbcache.api import kvstore
store = kvstore('postgresql://foo:bar@postgresql/mydb')
assert store.get('a') is None
store.set('a', 'aaa')
assert store.get('a') == 'aaa'
store.set('a', 'newvalue')
assert store.get('a') == 'newvalue'
store.delete('a')
assert store.get('a') is None
store.set('int', 42)
assert store.get('int') == 42
store.set('float', 42.0)
store.set('dict', {'a': [1, 2]})
assert store.all() == {
'dict': {'a': [1, 2]},
'float': 42.0,
'int': 42
}
assert store.keys() == ['dict', 'float', 'int']
Example usage (versioned key/value store):
from dbcache.api import vkvstore
vstore = vkvstore('postgresql://foo:bar@postgresql/mydb')
assert vstore.get('html') is None
v1 = datetime(2023, 1, 1, 12, 30, tzinfo=timezone.utc)
vstore.set(
'html',
b'<html></html>',
insertion_date=v1
)
assert vstore.get('html') == b'<html></html>'
v2 = datetime(2023, 1, 2, 12, 30, tzinfo=timezone.utc)
vstore.set(
'html',
b'<html>Hello, World</html>',
insertion_date=v2
)
assert vstore.get('html') == b'<html>Hello, World</html>'
assert vstore.get('html', insertion_date=v1) == b'<html></html>'
assert vstore.versions('html') == [
v1,
v2
]
assert vstore.versions('nope') == []
vstore.delete('html')
assert vstore.keys() == []
assert vstore.get('html') is None
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