[ZODB-Dev] Re: Database size increase on commit()

[Tres Seaver]

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tsmiller wrote:

> This is what my gut feeling was telling me.  Before I knew ANYTHING about
> the ZODB it seemed natural and easy to just use dictionaries as data
> structures for things such as accounts, books, dialogs, etc..   But it looks
> like the database saves the entire dictionary if anything in it changes.  Is
> this correct and is this why I need to use the PersistentMappings or BTrees?

Yes, you are correct.

> Why would I use one over the other?  

Both obey the "mapping protocol" used by Python.  PersistentMapping
tries harder to work like a dict;  the various BTee variants tend to
scale better when the mapping gets large, at the cost of O(logN) lookup
behavior, vs. O(1) amortizedd for the PM.



Tres.
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Tres Seaver          +1 540-429-0999          tseaver at palladion.com
Palladion Software   "Excellence by Design"    http://palladion.com
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