%META:TOPICPARENT{name="VirtTipsAndTricksGuide"}%

---+ How can I get full <code>explain</code> and <code>profile</code> plans for a simple SPARQL query?


Starting with Virtuoso Commercial Release 6.4, and Virtuoso Open Source 6.1.5, <code>isql</code> offers 2 new modes for analyzing SPARQL queries: 

   1 Translate a SPARQL query into the correspondent SQL: 
<verbatim>
SQL> SET SPARQL_TRANSLATE ON;
SQL> SELECT * FROM <graph> WHERE {?S a ?O};
       ---> Or execute query of your choice
SQL> SET SPARQL_TRANSLATE OFF;
</verbatim>
   1 Generate compilation plan of an SQL query:
<verbatim>   
SQL> SET EXPLAIN ON;
SQL> SELECT * FROM TABLE WHERE field = 'text';
     ---> Or execute query of your choice
SQL> SET EXPLAIN OFF;
</verbatim>   
      * The equivalent is <code>[[http://docs.openlinksw.com/virtuoso/fn_explain/][EXPLAIN()]]</code>, which is much more difficult to use; you cannot just copy-and-paste a query, as all quotes must be doubled within the <code>EXPLAIN(' ... ')</code>, as shown below:
<verbatim>      
SQL> explain('select * from table where field = ''text''');
</verbatim>
   1 Generate compilation and execution plan of an SQL query:
<verbatim>   
SQL> SET PROFILE ON;
SQL> SELECT * FROM TABLE WHERE field = 'text';
     ---> Or execute query of your choice
SQL> SET PROFILE OFF;
</verbatim>   
      * The equivalent (available in Virtuoso 7 and later) is <code>[[http://docs.openlinksw.com/virtuoso/fn_profile/][PROFILE()]]</code>, which is much more difficult to use; you cannot just copy-and-paste a query, as all quotes must be doubled within the <code>PROFILE(' ... ')</code>, as shown below:
<verbatim>      
SQL> profile('select * from table where field = ''text''');
</verbatim>
   1 A more detailed query profile (compilation and execution) with cardinality can be obtained by executing the following following sequence
<verbatim>
SQL> __dbf_set('enable_qr_comment', 1);             
SQL> __dbf_set('dbf_explain_level', 3);
SQL> SET PROFILE ON;
SQL> SET BLOBS ON;
SQL> SELECT * FROM TABLE WHERE field = 'text';
      ---> Or execute query of your choice
SQL> SET PROFILE OFF;
</verbatim>

Provide the generated plans for analysis.

---++ Example

Here is a simple example of how to combine the two options to get a full <code>explain()</code> plan for a simple SPARQL query: 


   1 Assume the following query:
<verbatim>
SELECT * 
FROM <http://dbpedia.org> 
WHERE 
  {
    ?s a ?o
  } 
LIMIT 10
</verbatim>
   1. Use the <code>isql</code> command line tool to connect to your database, and execute:
<verbatim>
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;
</verbatim>
   1. Use your mouse to select the query output, and paste it after the <code>SET EXPLAIN ON;</code> 
command.  Then hit the ENTER key.
<verbatim>	
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;
</verbatim>



---++Related

   * [[VirtTipsAndTricksGuide][Virtuoso Tips and Tricks Collection]]
   * [[http://docs.openlinksw.com/virtuoso/rdfsparql.html][Virtuoso Documentation]]