Exists (query directive)

Description

Includes rows where the inner directive returns a non-empty result using the row itself as input.

Constructor

Exists(Directive directive)

Notes

Note that the condition directive in If evaluates to true if it returns a non empty set. Thus it is usually unnecessary to wrap it inside an Exists directive.

Examples

importPackage(org.wandora.query2);
new Instances()
.where(new Exists(new Instances()))

This selects all instances of the input topic which have instances of their own.