Re: Fueski with Larq - query anomaly
On 24/10/12 12:11, Osma Suominen wrote: Hi Elli! It seems that at least part of your problem is having duplicates in the LARQ index. Have you tried creating the Lucene index using the larqbuilder command line tool, instead of removing the index and just letting Fuseki rebuild it when it starts? See the end of my tutorial [1] for a recipe. As I understand it, unless you give larqbuilder the --allow-duplicates option, it will try to avoid duplicates in the index. Though the index building will take longer. Exactly. Duplicate removal slow down indexing. In you want to index a large dataset you want to disable it and go faster. Maybe that option should be renamed. Proposal? Paolo I've also noticed that it usually makes sense to place the pf:textMatch pattern first in the query, otherwise it will be executed many times and slow down the whole query, sometimes by a lot. Hope this helps, -Osma [1] http://code.google.com/p/onki-light/wiki/InstallFusekiLARQ On Tue, 23 Oct 2012, Elli Schwarz wrote: Hello, I am using Fuseki with Larq (thanks to Osma's recent instructions - thanks Osma!) where I recompiled Jena (after adding the Larq dependency) to Jena revision 1399877 (this past Friday morning's version of the trunk). I'm noticing the following anomaly when querying the data: First I insert the following triples: prefix xsd: http://www.w3.org/2001/XMLSchema# insert data { graph urn:test:foo { urn:test:s1 urn:test:p1 foo^^xsd:string . urn:test:s1 urn:test:p2 foo^^xsd:string . urn:test:s2 urn:test:p3 foo^^xsd:string . } } Then I stop Fuseki, delete my index directory, and restart Fuseki. (As an aside, I'd be very interested in a fix for this so I don't have to restart Fuseki to rebuild the index - I'm watching JENA-164 and hoping someone will be able to work on it soon!) Once Fuseki is back up, I run the following query (I have default graph set as the union of named graphs by default): PREFIX pf: http://jena.hpl.hp.com/ARQ/property# select * where { urn:test:s1 ?p ?lit . ?lit pf:textMatch foo . } and I get 2 results as I expect: | p | lit | | urn:test:p1 | foo^^http://www.w3.org/2001/XMLSchema#string | | urn:test:p2 | foo^^http://www.w3.org/2001/XMLSchema#string | However, when I flip the order of my query like this: PREFIX pf: http://jena.hpl.hp.com/ARQ/property# select * where { ?lit pf:textMatch foo . urn:test:s1 ?p ?lit . I get 6 results, instead of the two I expect: | lit | p | | foo^^http://www.w3.org/2001/XMLSchema#string | urn:test:p1 | | foo^^http://www.w3.org/2001/XMLSchema#string | urn:test:p2 | | foo^^http://www.w3.org/2001/XMLSchema#string | urn:test:p1 | | foo^^http://www.w3.org/2001/XMLSchema#string | urn:test:p2 | | foo^^http://www.w3.org/2001/XMLSchema#string | urn:test:p1 | | foo^^http://www.w3.org/2001/XMLSchema#string | urn:test:p2 | My guess as to what happens is that in the second query, first the query executer executes the first line (the ?lit pf:textMatch foo) and this returns 3 results for foo, since there are 3 literals for foo. Then, the next line of the query has three bindings to ?lit, so it produces the 6 results above (2 for each foo literal since there are 2 properties for urn:test:s1). I know that I can avoid this by using a SELECT DISTINCT, but I still think the query shouldn't produce different results based on switching the order. Additionally, if I put this in a CONSTRUCT query, I can't use DISTINCT to eliminate the duplicate results (unless I use a SELECT DISTINCT subquery which I'd rather avoid). Another point I've noticed is that in my other (much more complex) queries, against a much larger dataset (~1.5 million triples), if I put the pf:textMatch line anywhere but in the very beginning of the query, the query takes a VERY long time to execute. If I put it as the first line in the query, the query runs quickly. My guess for this is that the query is executed in order, and it takes much more work for the query executer to run the other parts of my query which contain many results, and then have to go back and essentially filter out those results where the literal doesn't match the pf:textMatch. I can always place the pf:textMatch line first, but then I'm back to the problem mentioned above where I get back too many duplicate results. Thank you very much for your help! -Elli
Re: Fueski with Larq - query anomaly
Hi Osma, hi Elli On 02/11/12 10:34, Osma Suominen wrote: Hi Elli! [apparently your reply didn't come through the mailing list, but this one should] 31.10.2012 23:11, Elli Schwarz kirjoitti: Thank you for the tip. Yes, if I generate the index using the larqbuilder command, I don't get the duplicates in the query, regardless of the placement of the pf:testMatch line. (As an aside, why does the default behavior of creating the index allow duplicates, but the default of the larqbuilder command does not?) Good to hear that eliminating duplicates works for you. I have no idea why the defaults are as they are. LARQ index 'text' -- RDF nodes, see in IndexBuilderNode.java: public void index(Node node, String indexStr) { try { if ( avoidDuplicates() ) unindex(node, indexStr); Document doc = new Document() ; LARQ.store(doc, node) ; LARQ.index(doc, node, indexStr) ; getIndexWriter().addDocument(doc) ; } catch (IOException ex) { throw new ARQLuceneException(index, ex) ; } } avoidDuplicates() by default returns 'true' and by default we want to avoid duplicates and make the Lucene index smaller. if ( avoidDuplicates() ) unindex(node, indexStr); is 'ugly' and inefficient, but it is done to avoid having useless documents in the Lucene index, as you might have exactly the same RDF node/literal used in many triples. I am open to better suggestions to make this better or faster. However, switching the order of where I place the pf:textMatch line (while it may slow down the query), should not produce different results, even if there are duplicates in the index. This would appear to be a bug in how Larq applies the results of the index lookup to the query. Elli, could you provide an example with some data and your query? I'm not sure whether getting or not getting duplicates in specific situations can be considered a bug. But yes, the implementation of LARQ seems to be rather simplistic. It might help if the raw index results were filtered to weed out duplicates before applying them to the query. How could we do this? Then the choice whether to try to avoid duplicates during indexing would only be an optimization issue. BTW I'm not (so far) a LARQ developer, just a fellow user.. But you could help out with LARQ (if you are using it!). Patches are always welcome expecially from fellow users! ;-) By the way, many thanks for the documentation on how to use LARQ with Fuseki. Very useful (and it will save me time... I can just point people to your page from now on). Paolo -Osma Hi Elli! It seems that at least part of your problem is having duplicates in the LARQ index. Have you tried creating the Lucene index using the larqbuilder command line tool, instead of removing the index and just letting Fuseki rebuild it when it starts? See the end of my tutorial [1] for a recipe. As I understand it, unless you give larqbuilder the --allow-duplicates option, it will try to avoid duplicates in the index. Though the index building will take longer. I've also noticed that it usually makes sense to place the pf:textMatch pattern first in the query, otherwise it will be executed many times and slow down the whole query, sometimes by a lot. Hope this helps, -Osma [1] http://code.google.com/p/onki-light/wiki/InstallFusekiLARQ On Tue, 23 Oct 2012, Elli Schwarz wrote: Hello, I am using Fuseki with Larq (thanks to Osma's recent instructions - thanks Osma!) where I recompiled Jena (after adding the Larq dependency) to Jena revision 1399877 (this past Friday morning's version of the trunk). I'm noticing the following anomaly when querying the data: First I insert the following triples: prefix xsd: http://www.w3.org/2001/XMLSchema# insert data { graph urn:test:foo { urn:test:s1 urn:test:p1 foo^^xsd:string . urn:test:s1 urn:test:p2 foo^^xsd:string . urn:test:s2 urn:test:p3 foo^^xsd:string . } } Then I stop Fuseki, delete my index directory, and restart Fuseki. (As an aside, I'd be very interested in a fix for this so I don't have to restart Fuseki to rebuild the index - I'm watching JENA-164 and hoping someone will be able to work on it soon!) Once Fuseki is back up, I run the following query (I have default graph set as the union of named graphs by default): PREFIX pf: http://jena.hpl.hp.com/ARQ/property# select * where { urn:test:s1 ?p ?lit . ?lit pf:textMatch foo . } and I get 2 results as I expect: | p| lit | | urn:test:p1 | foo^^http://www.w3.org/2001/XMLSchema#string | | urn:test:p2 | foo^^http://www.w3.org/2001/XMLSchema#string | However, when I flip the order
Re: Fueski with Larq - query anomaly
On 16/11/12 22:20, Paolo Castagna wrote: Elli, could you provide an example with some data and your query? Apologies Elli, I now have found your example. ;-) Paolo
Re: Fueski with Larq - query anomaly
Hi Elli On 23/10/12 16:47, Elli Schwarz wrote: Hello, I am using Fuseki with Larq (thanks to Osma's recent instructions - thanks Osma!) where I recompiled Jena (after adding the Larq dependency) to Jena revision 1399877 (this past Friday morning's version of the trunk). I'm noticing the following anomaly when querying the data: First I insert the following triples: prefix xsd: http://www.w3.org/2001/XMLSchema# insert data { graph urn:test:foo { urn:test:s1 urn:test:p1 foo^^xsd:string . urn:test:s1 urn:test:p2 foo^^xsd:string . urn:test:s2 urn:test:p3 foo^^xsd:string . } } Then I stop Fuseki, delete my index directory, and restart Fuseki. (As an aside, I'd be very interested in a fix for this so I don't have to restart Fuseki to rebuild the index - I'm watching JENA-164 and hoping someone will be able to work on it soon!) Re: JENA-164 ... yeah, I'd love to help you out, but it's a sort of architectural issue of Jena IMHO. It should be easier for developers to listen to events as triples are added/removed so that you can attach external indexes and keep them in sync. There are multiple paths which you can use to change RDF data: APIs, SPARQL, etc. From a use point of view, you would like to keep your external index always in sync, no matter where the updates come from. Once Fuseki is back up, I run the following query (I have default graph set as the union of named graphs by default): PREFIX pf: http://jena.hpl.hp.com/ARQ/property# select * where { urn:test:s1 ?p ?lit . ?lit pf:textMatch foo . } and I get 2 results as I expect: | p | lit | | urn:test:p1 | foo^^http://www.w3.org/2001/XMLSchema#string | | urn:test:p2 | foo^^http://www.w3.org/2001/XMLSchema#string | However, when I flip the order of my query like this: PREFIX pf: http://jena.hpl.hp.com/ARQ/property# select * where { ?lit pf:textMatch foo . urn:test:s1 ?p ?lit . I get 6 results, instead of the two I expect: | lit | p | | foo^^http://www.w3.org/2001/XMLSchema#string | urn:test:p1 | | foo^^http://www.w3.org/2001/XMLSchema#string | urn:test:p2 | | foo^^http://www.w3.org/2001/XMLSchema#string | urn:test:p1 | | foo^^http://www.w3.org/2001/XMLSchema#string | urn:test:p2 | | foo^^http://www.w3.org/2001/XMLSchema#string | urn:test:p1 | | foo^^http://www.w3.org/2001/XMLSchema#string | urn:test:p2 | My guess as to what happens is that in the second query, first the query executer executes the first line (the ?lit pf:textMatch foo) and this returns 3 results for foo, since there are 3 literals for foo. Then, the next line of the query has three bindings to ?lit, so it produces the 6 results above (2 for each foo literal since there are 2 properties for urn:test:s1). I know that I can avoid this by using a SELECT DISTINCT, but I still think the query shouldn't produce different results based on switching the order. Additionally, if I put this in a CONSTRUCT query, I can't use DISTINCT to eliminate the duplicate results (unless I use a SELECT DISTINCT subquery which I'd rather avoid). I am not sure, at the moment I have no clear idea on how this problem could be fixed. Paolo Another point I've noticed is that in my other (much more complex) queries, against a much larger dataset (~1.5 million triples), if I put the pf:textMatch line anywhere but in the very beginning of the query, the query takes a VERY long time to execute. If I put it as the first line in the query, the query runs quickly. My guess for this is that the query is executed in order, and it takes much more work for the query executer to run the other parts of my query which contain many results, and then have to go back and essentially filter out those results where the literal doesn't match the pf:textMatch. I can always place the pf:textMatch line first, but then I'm back to the problem mentioned above where I get back too many duplicate results. Thank you very much for your help! -Elli
Re: Fueski with Larq - query anomaly
Hi Elli! [apparently your reply didn't come through the mailing list, but this one should] 31.10.2012 23:11, Elli Schwarz kirjoitti: Thank you for the tip. Yes, if I generate the index using the larqbuilder command, I don't get the duplicates in the query, regardless of the placement of the pf:testMatch line. (As an aside, why does the default behavior of creating the index allow duplicates, but the default of the larqbuilder command does not?) Good to hear that eliminating duplicates works for you. I have no idea why the defaults are as they are. However, switching the order of where I place the pf:textMatch line (while it may slow down the query), should not produce different results, even if there are duplicates in the index. This would appear to be a bug in how Larq applies the results of the index lookup to the query. I'm not sure whether getting or not getting duplicates in specific situations can be considered a bug. But yes, the implementation of LARQ seems to be rather simplistic. It might help if the raw index results were filtered to weed out duplicates before applying them to the query. Then the choice whether to try to avoid duplicates during indexing would only be an optimization issue. BTW I'm not (so far) a LARQ developer, just a fellow user.. -Osma Hi Elli! It seems that at least part of your problem is having duplicates in the LARQ index. Have you tried creating the Lucene index using the larqbuilder command line tool, instead of removing the index and just letting Fuseki rebuild it when it starts? See the end of my tutorial [1] for a recipe. As I understand it, unless you give larqbuilder the --allow-duplicates option, it will try to avoid duplicates in the index. Though the index building will take longer. I've also noticed that it usually makes sense to place the pf:textMatch pattern first in the query, otherwise it will be executed many times and slow down the whole query, sometimes by a lot. Hope this helps, -Osma [1] http://code.google.com/p/onki-light/wiki/InstallFusekiLARQ On Tue, 23 Oct 2012, Elli Schwarz wrote: Hello, I am using Fuseki with Larq (thanks to Osma's recent instructions - thanks Osma!) where I recompiled Jena (after adding the Larq dependency) to Jena revision 1399877 (this past Friday morning's version of the trunk). I'm noticing the following anomaly when querying the data: First I insert the following triples: prefix xsd: http://www.w3.org/2001/XMLSchema# insert data { graph urn:test:foo { urn:test:s1 urn:test:p1 foo^^xsd:string . urn:test:s1 urn:test:p2 foo^^xsd:string . urn:test:s2 urn:test:p3 foo^^xsd:string . } } Then I stop Fuseki, delete my index directory, and restart Fuseki. (As an aside, I'd be very interested in a fix for this so I don't have to restart Fuseki to rebuild the index - I'm watching JENA-164 and hoping someone will be able to work on it soon!) Once Fuseki is back up, I run the following query (I have default graph set as the union of named graphs by default): PREFIX pf: http://jena.hpl.hp.com/ARQ/property# select * where { urn:test:s1 ?p ?lit . ?lit pf:textMatch foo . } and I get 2 results as I expect: | p| lit | | urn:test:p1 | foo^^http://www.w3.org/2001/XMLSchema#string | | urn:test:p2 | foo^^http://www.w3.org/2001/XMLSchema#string | However, when I flip the order of my query like this: PREFIX pf: http://jena.hpl.hp.com/ARQ/property# select * where { ?lit pf:textMatch foo . urn:test:s1 ?p ?lit . I get 6 results, instead of the two I expect: | lit | p| | foo^^http://www.w3.org/2001/XMLSchema#string | urn:test:p1 | | foo^^http://www.w3.org/2001/XMLSchema#string | urn:test:p2 | | foo^^http://www.w3.org/2001/XMLSchema#string | urn:test:p1 | | foo^^http://www.w3.org/2001/XMLSchema#string | urn:test:p2 | | foo^^http://www.w3.org/2001/XMLSchema#string | urn:test:p1 | | foo^^http://www.w3.org/2001/XMLSchema#string | urn:test:p2 | My guess as to what happens is that in the second query, first the query executer executes the first line (the ?lit pf:textMatch foo) and this returns 3 results for foo, since there are 3 literals for foo. Then, the next line of the query has three bindings to ?lit, so it produces the 6 results above (2 for each foo literal since there are 2 properties for urn:test:s1). I know that I can avoid this by using a SELECT DISTINCT, but I still think the query
Re: Fueski with Larq - query anomaly
Hi Elli! It seems that at least part of your problem is having duplicates in the LARQ index. Have you tried creating the Lucene index using the larqbuilder command line tool, instead of removing the index and just letting Fuseki rebuild it when it starts? See the end of my tutorial [1] for a recipe. As I understand it, unless you give larqbuilder the --allow-duplicates option, it will try to avoid duplicates in the index. Though the index building will take longer. I've also noticed that it usually makes sense to place the pf:textMatch pattern first in the query, otherwise it will be executed many times and slow down the whole query, sometimes by a lot. Hope this helps, -Osma [1] http://code.google.com/p/onki-light/wiki/InstallFusekiLARQ On Tue, 23 Oct 2012, Elli Schwarz wrote: Hello, I am using Fuseki with Larq (thanks to Osma's recent instructions - thanks Osma!) where I recompiled Jena (after adding the Larq dependency) to Jena revision 1399877 (this past Friday morning's version of the trunk). I'm noticing the following anomaly when querying the data: First I insert the following triples: prefix xsd: http://www.w3.org/2001/XMLSchema# insert data { graph urn:test:foo { urn:test:s1 urn:test:p1 foo^^xsd:string . urn:test:s1 urn:test:p2 foo^^xsd:string . urn:test:s2 urn:test:p3 foo^^xsd:string . } } Then I stop Fuseki, delete my index directory, and restart Fuseki. (As an aside, I'd be very interested in a fix for this so I don't have to restart Fuseki to rebuild the index - I'm watching JENA-164 and hoping someone will be able to work on it soon!) Once Fuseki is back up, I run the following query (I have default graph set as the union of named graphs by default): PREFIX pf: http://jena.hpl.hp.com/ARQ/property# select * where { urn:test:s1 ?p ?lit . ?lit pf:textMatch foo . } and I get 2 results as I expect: | p | lit | | urn:test:p1 | foo^^http://www.w3.org/2001/XMLSchema#string | | urn:test:p2 | foo^^http://www.w3.org/2001/XMLSchema#string | However, when I flip the order of my query like this: PREFIX pf: http://jena.hpl.hp.com/ARQ/property# select * where { ?lit pf:textMatch foo . urn:test:s1 ?p ?lit . I get 6 results, instead of the two I expect: | lit | p | | foo^^http://www.w3.org/2001/XMLSchema#string | urn:test:p1 | | foo^^http://www.w3.org/2001/XMLSchema#string | urn:test:p2 | | foo^^http://www.w3.org/2001/XMLSchema#string | urn:test:p1 | | foo^^http://www.w3.org/2001/XMLSchema#string | urn:test:p2 | | foo^^http://www.w3.org/2001/XMLSchema#string | urn:test:p1 | | foo^^http://www.w3.org/2001/XMLSchema#string | urn:test:p2 | My guess as to what happens is that in the second query, first the query executer executes the first line (the ?lit pf:textMatch foo) and this returns 3 results for foo, since there are 3 literals for foo. Then, the next line of the query has three bindings to ?lit, so it produces the 6 results above (2 for each foo literal since there are 2 properties for urn:test:s1). I know that I can avoid this by using a SELECT DISTINCT, but I still think the query shouldn't produce different results based on switching the order. Additionally, if I put this in a CONSTRUCT query, I can't use DISTINCT to eliminate the duplicate results (unless I use a SELECT DISTINCT subquery which I'd rather avoid). Another point I've noticed is that in my other (much more complex) queries, against a much larger dataset (~1.5 million triples), if I put the pf:textMatch line anywhere but in the very beginning of the query, the query takes a VERY long time to execute. If I put it as the first line in the query, the query runs quickly. My guess for this is that the query is executed in order, and it takes much more work for the query executer to run the other parts of my query which contain many results, and then have to go back and essentially filter out those results where the literal doesn't match the pf:textMatch. I can always place the pf:textMatch line first, but then I'm back to the problem mentioned above where I get back too many duplicate results. Thank you very much for your help! -Elli -- Osma Suominen | osma.suomi...@aalto.fi | +358 40 5255 882 Aalto University, Department of Media Technology, Semantic Computing Research Group Room 2541, Otaniementie 17, Espoo, Finland; P.O. Box 15500, FI-00076 Aalto, Finland