How can I get a full explain plan for a simple SPARQL query?

Virtuoso Comercial Release 6.4 and Virtuoso Open Source 6.1.5 ISQL offers 2 new modes for analyzing SPARQL queries:

1. Translate a sparql query into the correspondent sql:
   

   
   SQL> SET SPARQL_TRANSLATE ON;
   SQL> SELECT * FROM <graph> WHERE {?S a ?O};
   SQL> SET SPARQL_TRANSLATE OFF;
   

   
   
2. Analyze a given SQL query:
   

   
   SQL> SET EXPLAIN ON;
   SQL> SELECT * FROM TABLE WHERE field = 'text';
   SQL> SET EXPLAIN OFF;
   

   
   
   • The quivalent is explain which is much more difficult to use since you cannot just cut and past a query as all quotes need to be doubled inside the explain (' ... '):
     

     
     SQL> explain('select * from table where field = ''text''');
     

     
     

Here is simple example of how to combine the two options to get a full explain plan for a simple SPARQL query:

1. Assume the following query:
   

   
   SELECT * 
   FROM <http://dbpedia.org> 
   WHERE 
     {
       ?s a ?o
     } 
   LIMIT 10
   

   
   
2. Connect using the ISQL command line tool to your database and execute:
   

   
   SQL> SET BLOBS ON;			-- in case output is very large
   SQL> SET SPARQL_TRANSLATE ON;
   SQL> SELECT * FROM <http://dbpedia.org> WHERE {?s a ?o} LIMIT 10;
   
   SPARQL_TO_SQL_TEXT
   VARCHAR
   _______________________________________________________________________________
   
   SELECT TOP 10 __id2i ( "s_1_0-t0"."S" ) AS "s",
     __ro2sq ( "s_1_0-t0"."O" ) AS "o"
   FROM DB.DBA.RDF_QUAD AS "s_1_0-t0"
   WHERE "s_1_0-t0"."G" = __i2idn ( __bft( 'http://dbpedia.org' , 1))
     AND  "s_1_0-t0"."P" = __i2idn ( __bft( 'http://www.w3.org/1999/02/22-rdf-syntax-ns#type' , 1))
   OPTION (QUIETCAST)
   
   1 Rows. -- 1 msec.
   
   SQL> SET SPARQL_TRANSLATE OFF;
   

   
   
3. Use mouse to select the above query output and paste it after the SET EXPLAIN ON; command. After pasting in the command, followed by the ENTER key:
   

   
   SQL> SET EXPLAIN ON;
   SQL> SELECT TOP 10 __id2i ( "s_1_0-t0"."S" ) AS "s", __ro2sq ( "s_1_0-t0"."O" ) AS "o"
    FROM DB.DBA.RDF_QUAD AS "s_1_0-t0"
    WHERE "s_1_0-t0"."G" = __i2idn ( __bft( 'http://dbpedia.org' , 1))
      AND  "s_1_0-t0"."P" = __i2idn ( __bft( 'http://www.w3.org/1999/02/22-rdf-syn tax-ns#type' , 1))
    OPTION (QUIETCAST)
   ;
   
   REPORT
   VARCHAR
   _______________________________________________________________________________
   
   { 
   from DB.DBA.RDF_QUAD by RDF_QUAD_POGS    4.5e+05 rows   
   Key RDF_QUAD_POGS  ASC ($22 "s_1_0-t0.S", $21 "s_1_0-t0.O")
    inlined <col=556 P =  #type >
   row specs: <col=554 G =  #http://dbpedia.org >
    
    
   After code:
         0: $25 "s" := Call __id2i ($22 "s_1_0-t0.S")
         5: $26 "o" := Call __ro2sq ($21 "s_1_0-t0.O")
         10: BReturn 0
   Select (TOP  10 ) ($25 "s", $26 "o", <$24 "<DB.DBA.RDF_QUAD s_1_0-t0>" spec 5>)
   }
   
   13 Rows. -- 1 msec.
   
   SQL> SET EXPLAIN OFF;
   

   
   

Related

• Virtuoso Tips and Tricks Collection
• Virtuoso Documentation