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Fwd: rdf.rb/spira bulk read question

From: Greg Lappen <greg@lapcominc.com>
Date: Wed, 2 Mar 2011 10:01:28 -0500
Message-ID: <AANLkTinr3NJqZWG57FdOs0r0qxii9e0fDJsxfLGwsFYi@mail.gmail.com>
To: public-rdf-ruby@w3.org
Actually, after further testing, I can say that even graph queries do a
query against the repository for each instance found.  For example, if I
execute this query:

query = RDF::Query.new(
  {:record=>
    {RDF.type => <class uri>,
     <property1_uri> => :property1,
     <property2_uri> => :property2}})

I see it does one query against the repo to get all statements with
predicate of <property1_uri>, then for each of those statements, it does
another query to get the  statements with predicate <property2_uri> that
have the same subject.  So again, hundreds of queries....am I missing
something, or is there really no way to get all properties for all instances
of a type out of the repository efficiently?

Greg

---------- Forwarded message ----------
From: Greg Lappen <greg@lapcominc.com>
Date: Wed, Mar 2, 2011 at 9:20 AM
Subject: rdf.rb/spira bulk read question
To: public-rdf-ruby@w3.org


Hi all,

We are making good progress with our project, and I've gotten to the point
where I am storing datasets in our rdf repository (rdf.rb based, implemented
on couchdb).  Now I'm building a page that allows the data to be exported in
various formats (xml, csv, etc), but when I iterate over all of the data, it
is extremely slow.  I see Spira querying the repository once for each
instance when I iterate using the model's "each" method.  I understand why,
I'm just wondering if there's a faster way to query all of the instances of
a Spira class.  One thought we had was to use a graph query instead, which
would pull out all the properties in N queries (where N is the number of
properties in the class).  In the example I'm trying, this would be 23
queries, which is better than hundreds or thousands of queries. Is this as
good as it gets?  I'm accustomed to working with RDBMS and ActiveRecord, so
I may just have to shift my expectations a bit, but thought I would ask the
group if there's something I'm missing....thanks as always,

Greg
Received on Wednesday, 2 March 2011 15:02:21 GMT

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