[ZODB-Dev] [BTrees] bad performance of intersection() over ZEO

[Andreas Jung]

Hi,

this morning I discovered that a statement

found = intersection(ids, idx) took up to 80 seconds.

'ids' -- OOTreeset (with up to 1000 items)
'idx' -- OOBTree (with up to 180K items, loaded through ZEO).

I assume that the worse performance comes from loading the whole OOBTree 
through
ZEO. Replacing the code with

found = OOSet()
for id in ids.keys():
   if idx.has_key(id):
      found.insert(id)

reduced the processing time to less than one second.

Is this a flaw in the implementation of intersection() or just 
broken-by-design?

Cheers,
Andreas