zope.app.generations utilities take all the memory

[Christophe Combelles]

zope.app.generations.utility.findObjectsMatching tries to parse the whole zodb, searching for container objects.
This procedure is intended to be run within a single transaction at startup or when the user launches an evolution script. Being run in a single transaction, this leads to raise the whole ZODB in the memory!

We should add some zodb cache management inside the generator loop, otherwise it's impossible to run an evolution script on a large database.
However I don't know the best solution for this. item._p_jar.cacheMinimize() ?

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Memory problems with looping is frequent and it would be probably a good idea to fix it directly in the ZODB, by implemeting some "anti-swap-to-death" stuffs in cache management. Users should be able to possibly tweak the cache for performance tuning, but they should never be forced to deal with it for simple tasks such as looping.