SQLite3Cache uses SA now

isso/__init__.py

@@ -180,7 +180,7 @@ def make_app(conf):
     if uwsgi is not None:
         cacheobj = cache.uWSGICache(timeout=3600)
     else:
-        cacheobj = cache.SQLite3Cache(db.SQLite3("/dev/shm/isso"), threshold=2048)
+        cacheobj = cache.SQLite3Cache(dbobj, threshold=2048)
 
     jobs = queue.Jobs()
     jobs.register("db-purge", dbobj, conf.getint("moderation", "purge-after"))

isso/cache/sqlite.py

@@ -4,42 +4,27 @@ from __future__ import absolute_import, unicode_literals
 
 import time
 
+from sqlalchemy.sql import select, func
+
 from . import Base
 
 
 class SQLite3Cache(Base):
-    """Implements a shared cache using SQLite3. Works across multiple processes
-    and threads, concurrent writes are not supported.
+    """Implements cache using SQLAlchemy Core.
 
-    JSON is used to serialize python primitives in a safe way.
+    JSON is used for safe serialization of python primitives.
     """
 
     serialize = True
 
-    def __init__(self, connection, threshold=1024, timeout=-1):
+    def __init__(self, db, threshold=1024, timeout=-1):
         super(SQLite3Cache, self).__init__(threshold, timeout)
-        self.connection = connection
-        self.connection.execute(
-            'CREATE TABLE IF NOT EXISTS cache ('
-            '    key TEXT PRIMARY KEY,'
-            '    value BLOB,'
-            '    time FLOAT)')
-
-        # drop trigger, in case threshold has changed
-        self.connection.execute('DROP TRIGGER IF EXISTS sweeper')
-        self.connection.execute([
-            'CREATE TRIGGER sweeper AFTER INSERT ON cache',
-            'BEGIN',
-            '    DELETE FROM cache WHERE key NOT IN ('
-            '        SELECT key FROM cache',
-            '        ORDER BY time DESC LIMIT {0}'.format(threshold),
-            '    );',
-            'END'])
-
-    def _get(self, ns, key, default=None):
-        rv = self.connection.execute(
-            'SELECT value FROM cache WHERE key = ?',
-            (ns + b'-' + key, )).fetchone()
+        self.db = db
+
+    def _get(self, ns, key):
+        rv = self.db.engine.execute(
+            select([self.db.cache.c.value]).where(
+                self.db.cache.c.key == ns + b'-' + key)).fetchone()
 
         if rv is None:
             raise KeyError
@@ -47,11 +32,36 @@ class SQLite3Cache(Base):
         return rv[0]
 
     def _set(self, ns, key, value):
-        with self.connection.transaction as con:
-            con.execute(
-                'INSERT OR REPLACE INTO cache (key, value, time) VALUES (?, ?, ?)',
-                (ns + b'-' + key, value, time.time()))
+        with self.db.transaction:
+            cnt = self.db.engine.execute(
+                select([func.count(self.db.cache)])).fetchone()[0]
+
+            if cnt + 1 > self.threshold:
+                self.db.engine.execute(
+                    self.db.cache.delete().where(
+                        self.db.cache.c.key.in_(select(
+                            [self.db.cache.c.key])
+                            .order_by(self.db.cache.c.time)
+                            .limit(1))))
+
+            try:
+                self._get(ns, key)
+            except KeyError:
+                insert = True
+            else:
+                insert = False
+
+            if insert:
+                stmt = self.db.cache.insert().values(
+                    key=ns + b'-' + key, value=value, time=time.time())
+            else:
+                stmt = self.db.cache.update().values(
+                    value=value, time=time.time()).where(
+                        self.db.cache.c.key == ns + b'-' + key)
+
+            self.db.engine.execute(stmt)
 
     def _delete(self, ns, key):
-        with self.connection.transaction as con:
-            con.execute('DELETE FROM cache WHERE key = ?', (ns + b'-' + key, ))
+        with self.db.transaction:
+            self.db.engine.execute(
+                self.db.cache.delete(self.db.cache.c.key == ns + b'-' + key))

isso/db/__init__.py

@@ -50,6 +50,11 @@ class Adapter(object):
             Column("key", String(255), primary_key=True),
             Column("value", String(255)))
 
+        self.cache = Table("cache", self.metadata,
+            Column("key", String(255), primary_key=True),
+            Column("value", LargeBinary(65535)),
+            Column("time", Float))
+
         self.metadata.create_all(self.engine)
         self.preferences = Preferences(self.engine, preferences)
 

isso/tests/test_cache.py

@@ -6,7 +6,7 @@ import unittest
 
 from isso.compat import text_type as str
 
-from isso.db import SQLite3
+from isso.db import Adapter
 from isso.cache import Cache, SQLite3Cache
 
 ns = "test"
@@ -56,4 +56,4 @@ class TestCache(unittest.TestCase):
 class TestSQLite3Cache(TestCache):
 
     def setUp(self):
-        self.cache = SQLite3Cache(SQLite3(":memory:"), threshold=8)
+        self.cache = SQLite3Cache(Adapter("sqlite:///:memory:"), threshold=8)