[redland-dev] size of bdb database
dave at dajobe.org
Fri Apr 7 04:55:22 BST 2006
Sébastien Pierre wrote:
> Hi Ethan,
> Le 06-04-04 à 16:09, Ethan Aubin a écrit :
>> I'm experimenting with redland today and having some problems
>> creating a store in Berkeley DB. The owl file I'm trying to import
>> is 46 M, but creating a new store has taken about 40 minutes so far
>> and the -po2s.db file has gotten over 5.3 gigs.
> It's funny, as I myself made some experiments with Redland and the BDD
>> This is on cygwin using redland 1.0.3 and bdb 4.4. Anyone have any
>> idea whats going on? Whats the normal size expansion storing rdf in bdb?
> My findings were that the storage scaled quite well (both in db size
> and in memory consumption), but that each statement as taking *2kb*,
> which is really too much. I ran some time ago a series of test which
> you can find here (http://wiki.type-z.org/index.php?
> n=Notes.RedlandStorageImpact), but sadly, I lost the associated images
> and code.
> It would be really good to have performance measurements and
> comparisons for Redland, between each storage, and compared to
> traditional relational databases.
That's way more testing than I've done on how it scales. I'm guessing
the overhead is due to these factors:
* the bdb backend stores indexes of an entire statement 3 times (+contexts)
* the entire parts of the statement are stored including URIs, not
pointers to short identifiers
* the statement varies in size
The assumption was it was better to have less I/O requests than to do
lots of read/writes to intern URIs. So it's a disk space vs time thing.
It might be interesting to compare with the sqlite backend which does
intern URIs, and probably works better for this size of data. I'm
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