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==Poor Performance==

===Debugging Poor SQL Query Performance===

Are you encountering poor performance issues with Virtuoso SQL queries? If so, use the {{{explain}}} function to troubleshoot this problem. The {{{explain}}} function compiles individual SQL statements and returns a description of the compilation. The description contains insight into join order, sub-query structure, and order of evaluation of predicates, and the splitting of distributed VDB queries across different data sources. This information is valuable to the detection of performance bottlenecks. Visit the following page for more information on use of {{{explain}}}:

http://docs.openlinksw.com/virtuoso/fn_explain.html

If you require assistance from <nop>OpenLink Product Support, be sure to provide {{{explain}}} output along with the original query, a Virtuoso server version string, and statement of whether or not you are using the Open Source or commercial edition.