PersistentDict: compress pickled data

Author: matthiasdiener

pytools/persistent_dict.py

@@ -582,14 +582,20 @@ def fetch(self, key, _stacklevel=0):
 
     @staticmethod
     def _read(path):
+        import lzma
         from pickle import load
-        with open(path, "rb") as inf:
-            return load(inf)
+        try:
+            with lzma.open(path, "rb") as inf:
+                return load(inf)
+        except lzma.LZMAError:
+            with open(path, "rb") as inf:
+                return load(inf)
 
     @staticmethod
     def _write(path, value):
+        import lzma
         from pickle import HIGHEST_PROTOCOL, dump
-        with open(path, "wb") as outf:
+        with lzma.open(path, "wb") as outf:
             dump(value, outf, protocol=HIGHEST_PROTOCOL)
 
     def _item_dir(self, hexdigest_key):