update: Rewrite update script

New update script uses futures to dynamically schedule many smaller
tasks between a constant number of threads, instead of statically
assigning a single long running task to each thread.
This results in better CPU saturation.

Database handles are not shared between threads anymore, instead
the main thread is used to commit results of other threads into the
database.
This trades locking on database access for serialization costs - since
multiprocessing is used, values returned from futures are pickled.
(although in practice that depends on ProcessPool configuration)

elixir/data.py

@@ -72,6 +72,14 @@ def iter(self, dummy=False):
         if dummy:
             yield maxId, None, None, None
 
+    def exists(self, idx, line_num):
+        entries = deflist_regex.findall(self.data)
+        for id, _, line, _ in entries:
+            if id == idx and int(line) == line_num:
+                return True
+
+        return False
+
     def append(self, id, type, line, family):
         if type not in defTypeD:
             return
@@ -165,6 +173,8 @@ def exists(self, key):
     def get(self, key):
         key = autoBytes(key)
         p = self.db.get(key)
+        if p is None:
+            return None
         p = self.ctype(p)
         return p
 
@@ -180,6 +190,9 @@ def put(self, key, val, sync=False):
         if sync:
             self.db.sync()
 
+    def sync(self):
+        self.db.sync()
+
     def close(self):
         self.db.close()