Projects/Nepomuk/VirtuosoInternal: Difference between revisions

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    (→‎List of tables: Data type)
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    * RDF_QUAD -- The main table which contains all the statements. It contains four rows "S", "P", "O" and "G" for the subject, predicate, object and graph.
    * RDF_QUAD -- The main table which contains all the statements. It contains four rows "S", "P", "O" and "G" for the subject, predicate, object and graph.
    * RDF_DATATYPE - Contains all the literal data types which are stored.
    * RDF_DATATYPE - Contains all the literal data types which are stored.
    * RDF_PREFIX
    * RDF_OBJ
    * RDF_LANGUAGE
    Read http://docs.openlinksw.com/virtuoso/rdfdatarepresentation.html to properly understand how virtuoso stores the data internally.


    = Default Indexes =
    = Default Indexes =

    Revision as of 10:15, 21 September 2012

    Connecting directly to virtuoso

    Virtuoso ships with an executable called isql-vt. Just running that executable should connect you to virtuoso.

    If you distribution does not provide the corresponding executable or if it doesn't work for you. Try this script -

    #!/bin/bash
    filename=`ps aux | grep virtuoso-t | grep -v grep | sed -e 's/.*\/tmp\///;s/ini.*/ini/'`
    port=$(grep ServerPort /tmp/$filename | sed -e 's/.*=//')
    exec isql-vt -S $port
    

    Running queries directly

    If for some reason you want to run queries directly on virtuoso, you'll need to connect to virtuoso via isql-vt and then type in the query. Make sure the query has the required prefixes and starts with the keyword sparql if it is a sparql query.

    I've attached a list of common prefixes for convenience -

    prefix nao: <http://www.semanticdesktop.org/ontologies/2007/08/15/nao#> 
    prefix nfo: <http://www.semanticdesktop.org/ontologies/2007/03/22/nfo#> 
    prefix nie: <http://www.semanticdesktop.org/ontologies/2007/01/19/nie#> 
    prefix ncal: <http://www.semanticdesktop.org/ontologies/2007/04/02/ncal#> 
    prefix nco: <http://www.semanticdesktop.org/ontologies/2007/03/22/nco#> 
    prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> 
    prefix pimo: <http://www.semanticdesktop.org/ontologies/2007/11/01/pimo#> 
    prefix nmo: <http://www.semanticdesktop.org/ontologies/2007/03/22/nmo#> 
    prefix nmm: <http://www.semanticdesktop.org/ontologies/2009/02/19/nmm#> 
    prefix nrl: <http://www.semanticdesktop.org/ontologies/2007/08/15/nrl#> 
    prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> 
    prefix xsd: <http://www.w3.org/2001/XMLSchema#>
    

    Example

    SQL> sparql prefix nco: <http://www.semanticdesktop.org/ontologies/2007/03/22/nco#> select ?r ?name where { ?r nco:fullname ?name . };
    

    List of tables

    is a relational database and what not

    All the tables in Virtuoso start with the DB.DBA. prefix.

    • RDF_QUAD -- The main table which contains all the statements. It contains four rows "S", "P", "O" and "G" for the subject, predicate, object and graph.
    • RDF_DATATYPE - Contains all the literal data types which are stored.
    • RDF_PREFIX
    • RDF_OBJ
    • RDF_LANGUAGE

    Read http://docs.openlinksw.com/virtuoso/rdfdatarepresentation.html to properly understand how virtuoso stores the data internally.

    Default Indexes

    Common Commands

    Apart from directly running SQL and SPARQL queries, virtuoso also provides some additional commands, which are listed over here.

    status

    The status() function can be used to return the current running queries on virtuoso.


    sparql_to_sql_text

    The sparql_to_sql_text() function can be used to convert a SPARQL query directly to the SQL it would be executed as.

    varchar sparql_to_sql_text
    ( in squery varchar );
    


    Example -

    SQL> select sparql_to_sql_text('prefix nco: <http://www.semanticdesktop.org/ontologies/2007/03/22/nco#> select ?r ?name where { ?r nco:fullname ?name . }');
    SPARQL_TO_SQL_TEXT
    VARCHAR
    _______________________________________________________________________________
    
    SELECT __id2i ( "s_1_0-t0"."S" ) AS "r",
      __ro2sq ( "s_1_0-t0"."O" ) AS "name"
    FROM DB.DBA.RDF_QUAD AS "s_1_0-t0"
    WHERE "s_1_0-t0"."P" = __i2idn ( __bft( 'http://www.semanticdesktop.org/ontologies/2007/03/22/nco#fullname' , 1))
    OPTION (QUIETCAST)
    
    1 Rows. -- 1 msec.
    


    It's very useful in debugging why many sparql queries are taking so long.