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<p class=MsoNormal>While looking at Sparql performance I noticed that some of
the calls from the Rascal library to librdf_storage_find_statements() contained
a statement with all three nodes completely specified.<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>As currently coded having all three nodes defined prevents
the use of the efficient storage back end methods (find_sources(), find_arcs(),
and find_targets()) when configured with a hashed storage module like the Berkeley
DB.<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>I would like to change this behavior.<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>To handle the case where a complete statement is passed into
librdf_storage_find_statements(), I wanted to add the following:<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoListParagraph style='margin-left:.75in;text-indent:-.25in;
mso-list:l0 level1 lfo1'><![if !supportLists]><span style='mso-list:Ignore'>1.<span
style='font:7.0pt "Times New Roman"'> </span></span><![endif]>Call
find_targets() with the subject and predicate nodes from the passed in
statement.<o:p></o:p></p>
<p class=MsoListParagraph style='margin-left:.75in;text-indent:-.25in;
mso-list:l0 level1 lfo1'><![if !supportLists]><span style='mso-list:Ignore'>2.<span
style='font:7.0pt "Times New Roman"'> </span></span><![endif]>Use
the iterator returned from find_targets() to iterate over the target nodes checking
for the object node that matches the object node from the passed in statement.<o:p></o:p></p>
<p class=MsoListParagraph style='margin-left:.75in;text-indent:-.25in;
mso-list:l0 level1 lfo1'><![if !supportLists]><span style='mso-list:Ignore'>3.<span
style='font:7.0pt "Times New Roman"'> </span></span><![endif]>If
the object node does not exists, return an empty stream by calling
librdf_new_empty_stream().<o:p></o:p></p>
<p class=MsoListParagraph style='margin-left:.75in;text-indent:-.25in;
mso-list:l0 level1 lfo1'><![if !supportLists]><span style='mso-list:Ignore'>4.<span
style='font:7.0pt "Times New Roman"'> </span></span><![endif]>If
the object node does exists, create a stream from the statement.<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Step 4 is where I am stuck. The iterator from step one
can’t be used in the call to librdf_new_stream_from_node_iterator() because
it may contain more than the desired object node. <o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>In the example below this could be caused by multiple “lou:hobby”
properties.<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoPlainText>Here is a copy of the query.<o:p></o:p></p>
<p class=MsoPlainText><o:p> </o:p></p>
<p class=MsoPlainText>PREFIX lou: <<a href="http://ns.lou.com/2007/lou-ns#">http://ns.lou.com/2007/lou-ns#</a>>
<o:p></o:p></p>
<p class=MsoPlainText>PREFIX xsd: <<a
href="http://www.w3.org/2001/XMLSchema#">http://www.w3.org/2001/XMLSchema#</a>><o:p></o:p></p>
<p class=MsoPlainText>SELECT * WHERE {<o:p></o:p></p>
<p class=MsoPlainText>?subject lou:Sex ‘male’.<o:p></o:p></p>
<p class=MsoPlainText>?subject lou:hobby ‘camping’.<o:p></o:p></p>
<p class=MsoPlainText>?subject lou:BirthDate ?p1.<o:p></o:p></p>
<p class=MsoPlainText> FILTER (<o:p></o:p></p>
<p class=MsoPlainText> ( (xsd:dateTime(?p1) <=<o:p></o:p></p>
<p class=MsoPlainText> xsd:dateTime('2008-01-31T00:00:00')) &&
(xsd:dateTime(?p1) >=<o:p></o:p></p>
<p class=MsoPlainText> xsd:dateTime('2008-01-01T00:00:00')) )<o:p></o:p></p>
<p class=MsoPlainText> ) }<o:p></o:p></p>
<p class=MsoPlainText><o:p> </o:p></p>
<p class=MsoPlainText><o:p> </o:p></p>
<p class=MsoPlainText>It is expected to find all males born in January of 2008
that have a camping hobby.<o:p></o:p></p>
<p class=MsoPlainText><o:p> </o:p></p>
<p class=MsoPlainText><o:p> </o:p></p>
<p class=MsoPlainText><o:p> </o:p></p>
<p class=MsoNormal>Thanks in advance.<o:p></o:p></p>
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