Help:$smwgQFilterDuplicates

is a configuration parameter that sets whether duplicate query conditions (segments) should be removed from computing query results. Thus the computational effort for conditions (segments) that represent that same query signature is being eliminated. The impact of this optimization is currently unknown. The configuration parameter was introduced in .CiteRef::gh:smw:2176

The idea behind this configuration parameter is to filter some query segments (the part that represents individual SQL statements of a query, i.e. query conditions) that can be duplicate and would create an additional temp table which in return would lengthen the time the SQL engine needs to answer the query. If enabled Semantic MediaWiki tries to match the fingerprint of a description and replaces the reference if matched before the "QueryEngine" becomes aware of the segments.

Default setting
This means that duplicate query segments are not being removed from computing query results.

Changing the default setting
To modify the setting to this configuration parameter, add one of the following lines to your "LocalSettings.php" file after the  call:

This means that duplicate query segments are being removed from computing query results.
 * Enable duplicate query conditions being removed from computing query results