Fred Drake wrote:
I have a need for 64-bit BTrees (at least for IOBTree and OIBTree), and I'm not the first. I've created a feature development branch for this, and checked in my initial implementation.
I've modified the existing code to use PY_LONG_LONG instead of int for the key and/or value type; there's no longer a 32-bit version in the modified code. Any Python int or long that can fit in 64 bits is accepted; ValueError is raised for values that require 65 bits (or more). Keys and values that can be reported as Python ints are, and longs are only returned when the value cannot be converted to a Python int.
This can have a substantial effect on memory consumption, since keys and/or values now take twice the space. There may be performance issues as well, but those have not been tested.
There are new unit tests, but more are likely needed.
If you're interested in getting the code from Subversion, it's available at:
svn://svn.zope.org/repos/main/ZODB/branches/fdrake-64bits/
Ideally, this or some variation on this could be folded back into the main development for ZODB. If this is objectionable, making 64-bit btrees available would require introducing new versions of the btrees (possibly named LLBTree, LOBTree, and OLBTree).
-1 to the L*BTree flavours. The 'long' type is disappearing from Python anyways, why should the implementation detail worry us regarding BTrees? +1 to making the I*BTree flavours 64bit-aware. If Jim is right, existing pickles will be read back just fine and as long as the integers stay under 32 bit, they won't even be bigger. The only real implication therefore is the pushing around twice as many bits in memory. Dieter estimates 20% to 35% slowdown for the C algorithms (whatever that means), Tim seems to think it won't have such a big effect. I guess we'll only know after some benchmarks. Philipp