sqlite quality fixes

src/storage/sqlite.py

@@ -1,6 +1,5 @@
 """
-src/storage/sqlite.py
-=========================
+Sqlite Inventory
 """
 import sqlite3
 import time
@@ -10,7 +9,7 @@ from helper_sql import sqlQuery, SqlBulkExecute, sqlExecute
 from storage import InventoryStorage, InventoryItem
 
 
-class SqliteInventory(InventoryStorage):    # pylint: disable=too-many-ancestors
+class SqliteInventory(InventoryStorage):  # pylint: disable=too-many-ancestors
     """Inventory using SQLite"""
     def __init__(self):
         super(SqliteInventory, self).__init__()
@@ -20,9 +19,11 @@ class SqliteInventory(InventoryStorage):    # pylint: disable=too-many-ancestors
         # cache for existing objects, used for quick lookups if we have an object.
         # This is used for example whenever we receive an inv message from a peer
         # to check to see what items are new to us.
-        # We don't delete things out of it; instead, the singleCleaner thread clears and refills it.
+        # We don't delete things out of it; instead,
+        # the singleCleaner thread clears and refills it.
         self._objects = {}
-        # Guarantees that two receiveDataThreads don't receive and process the same message concurrently
+        # Guarantees that two receiveDataThreads don't receive
+        # and process the same message concurrently
         # (probably sent by a malicious individual)
         self.lock = RLock()
 
@@ -30,7 +31,9 @@ class SqliteInventory(InventoryStorage):    # pylint: disable=too-many-ancestors
         with self.lock:
             if hash_ in self._objects:
                 return True
-            rows = sqlQuery('SELECT streamnumber FROM inventory WHERE hash=?', sqlite3.Binary(hash_))
+            rows = sqlQuery(
+                'SELECT streamnumber FROM inventory WHERE hash=?',
+                sqlite3.Binary(hash_))
             if not rows:
                 return False
             self._objects[hash_] = rows[0][0]
@@ -41,8 +44,8 @@ class SqliteInventory(InventoryStorage):    # pylint: disable=too-many-ancestors
             if hash_ in self._inventory:
                 return self._inventory[hash_]
             rows = sqlQuery(
-                'SELECT objecttype, streamnumber, payload, expirestime, tag FROM inventory WHERE hash=?',
-                sqlite3.Binary(hash_))
+                'SELECT objecttype, streamnumber, payload, expirestime, tag'
+                ' FROM inventory WHERE hash=?', sqlite3.Binary(hash_))
             if not rows:
                 raise KeyError(hash_)
             return InventoryItem(*rows[0])
@@ -64,35 +67,49 @@ class SqliteInventory(InventoryStorage):    # pylint: disable=too-many-ancestors
 
     def __len__(self):
         with self.lock:
-            return len(self._inventory) + sqlQuery('SELECT count(*) FROM inventory')[0][0]
+            return len(self._inventory) + sqlQuery(
+                'SELECT count(*) FROM inventory')[0][0]
 
     def by_type_and_tag(self, objectType, tag):
+        """Return objects filtered by object type and tag"""
         with self.lock:
-            values = [value for value in self._inventory.values() if value.type == objectType and value.tag == tag]
+            values = [value for value in self._inventory.values()
+                      if value.type == objectType and value.tag == tag]
             values += (InventoryItem(*value) for value in sqlQuery(
-                'SELECT objecttype, streamnumber, payload, expirestime, tag \
-                FROM inventory WHERE objecttype=? AND tag=?', objectType, sqlite3.Binary(tag)))
+                'SELECT objecttype, streamnumber, payload, expirestime, tag'
+                ' FROM inventory WHERE objecttype=? AND tag=?',
+                objectType, sqlite3.Binary(tag)))
             return values
 
     def unexpired_hashes_by_stream(self, stream):
+        """Return unexpired inventory vectors filtered by stream"""
         with self.lock:
             t = int(time.time())
-            hashes = [x for x, value in self._inventory.items() if value.stream == stream and value.expires > t]
+            hashes = [x for x, value in self._inventory.items()
+                      if value.stream == stream and value.expires > t]
             hashes += (str(payload) for payload, in sqlQuery(
-                'SELECT hash FROM inventory WHERE streamnumber=? AND expirestime>?', stream, t))
+                'SELECT hash FROM inventory WHERE streamnumber=?'
+                ' AND expirestime>?', stream, t))
             return hashes
 
     def flush(self):
+        """Flush cache"""
         with self.lock:
-            # If you use both the inventoryLock and the sqlLock, always use the inventoryLock OUTSIDE of the sqlLock.
+            # If you use both the inventoryLock and the sqlLock,
+            # always use the inventoryLock OUTSIDE of the sqlLock.
             with SqlBulkExecute() as sql:
                 for objectHash, value in self._inventory.items():
-                    sql.execute('INSERT INTO inventory VALUES (?, ?, ?, ?, ?, ?)', sqlite3.Binary(objectHash), *value)
+                    sql.execute(
+                        'INSERT INTO inventory VALUES (?, ?, ?, ?, ?, ?)',
+                        sqlite3.Binary(objectHash), *value)
                 self._inventory.clear()
 
     def clean(self):
+        """Free memory / perform garbage collection"""
         with self.lock:
-            sqlExecute('DELETE FROM inventory WHERE expirestime<?', int(time.time()) - (60 * 60 * 3))
+            sqlExecute(
+                'DELETE FROM inventory WHERE expirestime<?',
+                int(time.time()) - (60 * 60 * 3))
             self._objects.clear()
             for objectHash, value in self._inventory.items():
                 self._objects[objectHash] = value.stream