Roché Compaan wrote at 2008-8-23 19:31 +0200: >On Sat, 2008-08-23 at 14:09 +0200, Dieter Maurer wrote: >> Roché Compaan wrote at 2008-8-22 14:49 +0200: >> >I've been doing some benchmarks on Plone and got some surprising stats >> >on the pickle size of btrees and their buckets that are persisted with >> >each transaction. Surprising in the sense that they are very big in >> >relation to the actual data indexed. I would appreciate it if somebody >> >can help me understand what is going on, or just take a look to see if >> >the sizes look normal. >> > >> >In the benchmark I add and index 10000 ATDocuments. I commit after each >> >document to simulate a transaction per request environment. Each >> >document has a 100 byte long description and 100 bytes in it's body. The >> >total transaction size however is 40K in the beginning. The transaction >> >sizes grow linearly to about 350K when reaching 10000 documents. >> >> The "Bucket" nodes store usually between 22 ("OOBucket") and 90 ("IIBucket") >> objects in a single bucket. >> >> With any change, the transaction will contain unmodified data >> for several dozens other objects. > >Are you saying *all* 22 OOBuckets and 90 IIBuckets will be persisted >again whether they are modified or not?
I did not speak of "22 OOBuckets" but of typically 22 entries in an "OOBucket" (similarly for "IIBucket"). And indeed, when a single entry in an "OOBucket" is changed, then all entries are rewritten even if the other entries did not change. That is because the ZODB load/store granularity is the persistent object (without persistent subobjects). An "OOBucket" is a persistent object -- it is loaded/stored always as a whole (all entries together). -- Dieter _______________________________________________ For more information about ZODB, see the ZODB Wiki: http://www.zope.org/Wikis/ZODB/ ZODB-Dev mailing list - ZODB-Dev@zope.org http://mail.zope.org/mailman/listinfo/zodb-dev