Hello all,
I got Virtuoso working without iodbc config flag and used isql to
benchmark some queries on rdf data sets from 5 to 200.000 triples.
As expected, Virtuoso was the fastest among the tested engines; a bit
more than twice as fast as my engine (that is in RAP, RDF API for PHP)
and even more fast than the other engines (Redland, Jena, ARC).
Once I come to rest I will publish the detailled results.
What I would like to know you is that Virtuoso's SPARQL engine has some
problems with certain queries that work flawless on other engines:
--------
SQL> sparql SELECT ?s WHERE {?s ?p ?o. FILTER(regex(?o, "Education"))};
*** Error 22023: [Virtuoso Driver][Virtuoso Server]SR375: Invalid
argument 2 to regexp_match. Must be narrow or wide string at line 1 of
Top-Level:
--------
SQL> sparql PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
SELECT ?publ ?p1 ?p1mail ?p2 ?p2mail ?p3 ?p3mail WHERE { ?publ
<http://test/#publicationAuthor> ?p1. ?p1
<http://test/#emailAddress> ?p1mail OPTIONAL { ?publ
<http://test/#publicationAuthor> ?p2. ?p2
<http://test/#emailAddress> ?p2mail. FILTER(?p1 != ?p2)}OPTIONAL
{ ?publ <http://test/#publicationAuthor> ?p3. ?p3
<http://test/#emailAddress> ?p3mail. FILTER(?p1 != ?p3
&& ?p2 != ?p3) }} LIMIT 10;
*** Error 37000: [Virtuoso Driver][Virtuoso Server]SQ074: Line 1:
SP031: SPARQL compiler: Variable 'p2' is used in subexpressions of the
query but not assigned at ';' immediately before end of statement at
line 2 of Top-Level:
--------
Beside that I found it to be a huge pain in the stomach that Virtuoso
does not have a native way to delete rows and limit the number of rows.
In e.g. MySQL you can do
> DELETE FROM table LIMIT 10
which would delete 10 rows only. Sometimes (as in my case) it does not
matter at all which rows are deleted, only the number counts.
I tried both SQL and SPARQL.
In the end I wrote my own stored procedure that has a parameter of the
number of rows to delete and selects always one single row and deletes
it until a counter reaches the desired number.
--
Regards/Mit freundlichen Grüßen
Christian Weiske
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