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  • VOS.VirtTipsAndTricksAnalyzingSPARQLQuery(Last) -- Owiki? , 2018-04-13 12:08:30 Edit owiki 2018-04-13 07:08:30

    How can I get a full explain and profile plans for a simple SPARQL query?

    Starting with Virtuoso Commercial 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}; ---> Or execute query of your choice SQL> SET SPARQL_TRANSLATE OFF;

    2. Generate compilation plan of an SQL query:

      SQL> SET EXPLAIN ON; SQL> SELECT * FROM TABLE WHERE field = 'text'; ---> Or execute query of your choice SQL> SET EXPLAIN OFF;

      • The equivalent is EXPLAIN(), which is much more difficult to use; you cannot just copy-and-paste a query, as all quotes must be doubled within the EXPLAIN(' ... '), as shown below:

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

    3. Generate compilation and execution plan of an SQL query:

      SQL> SET PROFILE ON; SQL> SELECT * FROM TABLE WHERE field = 'text'; ---> Or execute query of your choice SQL> SET PROFILE OFF;

      • The equivalent (available in Virtuoso 7 and later) is PROFILE(), which is much more difficult to use; you cannot just copy-and-paste a query, as all quotes must be doubled within the PROFILE(' ... '), as shown below:

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

    4. A more detailed query profile (compilation and execution) with cardinality can be obtained by executing the following following sequence

      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;

      Provide the generated plans for analysis.

    Here is a 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. Use the isql command line tool to connect 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 your mouse to select the query output, and paste it after the SET EXPLAIN ON; command. Then hit 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;

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