Re: [Virtuoso-users] DB.DBA.RDF_GEO_FILL exits with error
Hi Claus, The first time the after a DB start DB.DBA.RDF_GEO_FILL () is called, the error occurs after less than a half a minute. On consecutive attempts it then only takes a few seconds. The error occurs independent of whether resources carry the virtuoso specific geo-literals. However, as already mentionend, adding those seems to be a workaround for that issue. This problem is fixed in the new build. I will contact you shortly where to get a new binary from. Patrick
Re: [Virtuoso-users] Mac re-install error
Hi Nico,
I installed virtuoso already once on another server.
But this time I have some problems while compiling.
This files are not there, and they are not in the files I downloaded.
The source archive does not have this file either, but sometimes
external tools like editors etc create such local files. I will see if
i can fix the script so it filters out such files in a following
release of VOS.
In the mean time, please perform the following commands:
First we clean up the directory:
cd binsrc/rdf_mappers
gmake clean
Next we check this unwanted file is there and remove it:
cd main/xslt
ls -l ._abmeta2rdfxml.xsl
rm ._abmeta2rdfxml.xsl
Next we rebuild the vad package:
cd ../..
gmake
Please let me know if this resolves your build problem.
Patrick
The output:
=
= STARTED RDF Mappers PACKAGING
= Mon Jul 12 18:51:07 BST 2010
=
Shutdown Virtuoso Server...
VAD Sticker vad_dav.xml creation...
VAD Sticker vad_fs.xml creation...
Virtuoso.ini creation...
Waiting Virtuoso Server start on port ...
PASSED: Virtuoso Server successfully started on port
***FAILED: execution of DB.DBA.VAD_PACK('vad_fs.xml', '.',
'rdf_mappers_filesystem.vad')
SQL ERROR -
*** Error 42VAD: [Virtuoso Driver][Virtuoso Server]Inexistent file
resource (./vad/vsp/rdf_mappers/xslt/main/._abmeta2rdfxml.xsl)
in
signal:(BIF),
VAD.DBA.VAD_FAIL_CHECK,
VAD.DBA.VAD_OUT_ROW_FILE,
VAD.DBA.VAD_TEST_CREATE,
DB.DBA.VAD_PACK,
Top Level
at line 0 of Top-Level:
DB.DBA.VAD_PACK('vad_fs.xml', '.', 'rdf_mappers_filesystem.vad')
PASSED: commit work
PASSED: checkpoint
***FAILED: execution of DB.DBA.VAD_PACK('vad_dav.xml', '.',
'rdf_mappers_dav.vad')
SQL ERROR -
*** Error 42VAD: [Virtuoso Driver][Virtuoso Server]Inexistent file
resource (./vad/vsp/rdf_mappers/xslt/main/._abmeta2rdfxml.xsl)
in
signal:(BIF),
VAD.DBA.VAD_FAIL_CHECK,
VAD.DBA.VAD_OUT_ROW_FILE,
VAD.DBA.VAD_TEST_CREATE,
DB.DBA.VAD_PACK,
Top Level
at line 0 of Top-Level:
DB.DBA.VAD_PACK('vad_dav.xml', '.', 'rdf_mappers_dav.vad')
PASSED: commit work
PASSED: checkpoint
Shutdown Virtuoso Server...
=
= Checking log file /data/virtuoso-opensource-6.1.0/binsrc/
rdf_mappers/make_rdf_mappers_vad.log for statistics:
=
= Total number of tests PASSED : 5
= Total number of tests FAILED : 2
= Total number of tests ABORTED : 0
=
*** Not all tests completed successfully
*** Check the file /data/virtuoso-opensource-6.1.0/binsrc/
rdf_mappers/make_rdf_mappers_vad.log for more information # egrep \*
\*.*FAILED:|\*\*.*ABORTED: /data/virtuoso-opensource-6.1.0/binsrc/
rdf_mappers/make_rdf_mappers_vad.log
make[2]: *** [rdf_mappers_dav.vad] Error 1
make[2]: Leaving directory `/data/virtuoso-opensource-6.1.0/binsrc/
rdf_mappers'
make[1]: *** [all-recursive] Error 1
make[1]: Leaving directory `/data/virtuoso-opensource-6.1.0/binsrc'
make: *** [all-recursive] Error 1
Re: [Virtuoso-users] SQL subquery embedded in a SPARQL query
On 14.07.2010 4:38, Ted Thibodeau Jr wrote: While not exactly what you're asking for, this may be sufficient for what you want to achieve -- http://docs.openlinksw.com/virtuoso/rdfsparql.html#rdfsqlfromsparql Yes, we have seen this, but this will be very inefficient for large datasets. We actually want to experiment with such a feature for increasing the performance of the triple store, by replicating commonly queried information structures in relational tables. The second use case would be integration of really large datasources and also there it would be crucial, that the whole resulting query could be optimized by Virtuoso's query optimizer. Best, Sören
Re: [Virtuoso-users] SQL subquery embedded in a SPARQL query
Hello Sören,
First of all, placing the SQL query into SPARQL is required less
frequently than it seems to be. Virtuoso's optimizer does not treat
subquery as an instruction to preserve the order. As a result,
PREFIX : http://people.example/
SELECT ?y ?name ?age WHERE {
:alice :knows ?y .
{
SQL SELECT y, name, age FROM people
}
}
and
select q1.y, q2.name, q2.age
from (sparql
PREFIX : http://people.example/
SELECT ?y WHERE { :alice :knows ?y } ) as q1.
people as q2
where q2.y=q1.y
will probably produce equivalent execution plans.
However, native SQLs could be very useful (and sometimes unavoidable) in nested
scalar subqueries, e.g. in FILTER(bif:exists(...))
or in
SPARQL select
(select ...) as ?calculated-value1
(select ...) as ?calculated-value-2
where ...
The problem is that the sparql compiler may copy the content of the sql
subquery into many places of the resulting big sql query.
If the subquery refers to some aliases then multiple copies of these aliases
may cause weird SQL compilation errors.
Even worse, the subquery may omit aliases making things more obfuscating.
Finally, the subquery will probably refer to variables bound in surrounding
SPARQL so that variables should be recognized in the text of the query and
appropriate aliases should be imprinted before them.
A dirty hack is to write an RDF view that creates triples using tables, joins
and filter conditions from the SQL query in question.
That will make the optimizer happy and provide best possible SQL code but it's
next to unusable if there are many different subqueries.
Or better write an RDF view that creates triples using tables and maybe some
joins from the SQL query in question but place filters and remaining joins into
SPARQL query over that view.
That's more flexible and the quality of the generated code will stay good.
However the RDF View is a bad choice if an SQL view should be used as a source,
or not applicable at all if the SQL view is actually procedure view.
So I should think what could be done.
Right now SPARQL compiler is a preprocessor at the front of the compiler.
To handle arbitrary SQL subqueries, the SQL processor should be divided in
parts, so there will be an SQL+SPARQL preprocessor, then SPARQL processor then
core of the SQL compiler, not a small change.
As a variant, the SQL inside SPARQL will contain special easily recognizable
syntax extensions to refer to variables of surrounding SPARQL (and variables of
SQL code around surrounding SPARQL).
I will discuss the issue with others and return to this topic after the release
that will contain SPARQL 1.1 extensions.
Best Regards,
Ivan Mikhailov
OpenLink Software
http://virtuoso.openlinksw.com
On Wed, 2010-07-14 at 13:55 +0200, Sören Auer wrote:
Hi,
For some experiments we plan to run it would be very useful to embed an
SQL query as a subquery inside a SPARQL query. We want to combine
relational with RDF data for example in the following way:
Lets assume we have foaf profiles in the triple store and a relational
table with information about people (e.g. from a CRM system). A query
similar to the following would be really useful in that case:
PREFIX : http://people.example/
SELECT ?y ?name ?age WHERE {
:alice :knows ?y .
{
SQL SELECT y, name, age FROM people
}
}
Instead of joining with the triple table a join with the SQL subquery
would occur and SPARQL variables would be matched against columns of the
SQL result set with the same name.
Does this make sense? Are there already plans to implement something
along these lines in Virtuoso? I think this functionality would
dramatically simplify a number of data integration tasks and be a
wonderful USP for Virtuoso.
Best,
Sören
