[ZODB-Dev] BTrees and id mapping (was Re: Data.fs size grows non-stop)

Tres Seaver tseaver at palladion.com
Mon Dec 14 16:49:23 EST 2009

Hash: SHA1

Pedro Ferreira wrote:
> David Glick wrote:
>> Pedro Ferreira wrote:
>>> Hello all,
>>> So, I've been experimenting with a new structure for our date indexes, 
>>> and I was considering using an IOBTree that would map integer timestamps 
>>> to BTree-based sets. As for the sets, I considered two options:
>> Be careful with using timestamps as IOBTree keys.  By default this type 
>> of BTree uses the system integer, which on many systems is 32 bits.  
>> That means that you'll overflow the maximum allowed key for timestamps 
>> beyond the year 2038.  It won't even give an error; it will just 
>> silently overflow and overwrite existing values in the BTree.
> Yes, I know. That's one of the reasons I'm using YYYYmmdd integers 
> instead (the other one being i only need 1 day resolution).
> Thanks a lot for the tip!

An LOBTree uses a guaranteed-to-be-long (64 bits) integer for the keys,
if you need that.

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Tres Seaver          +1 540-429-0999          tseaver at palladion.com
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