[Zope-CVS] CVS: Products/ZCTextIndex - Index.py:1.1.2.23

[Jeremy Hylton]

Update of /cvs-repository/Products/ZCTextIndex
In directory cvs.zope.org:/tmp/cvs-serv16278

Modified Files:
      Tag: TextIndexDS9-branch
	Index.py 
Log Message:
Add further comment explaining why IIBTrees are a more efficient
in-memory representation than dictionaries.


=== Products/ZCTextIndex/Index.py 1.1.2.22 => 1.1.2.23 ===
         # IIBTree with 10 elts, and 10 happens to be 2/3s of 2**4.  So
         # choose 10 as the cutoff for now.
+
+        # The IIBTree has a smaller in-memory representation than a
+        # dictionary, so pickle size isn't the only consideration when
+        # choosing the threshold.  The pickle of a 500-elt dict is 92%
+        # of the size of the same IIBTree, but the dict uses more
+        # space when it is live in memory.  An IIBTree stores two C
+        # arrays of ints, one for the keys and one for the values.  It
+        # holds upto 120 key-value pairs in a single bucket.
         try:
             map = self._wordinfo[wid]
         except KeyError: