Filter.java

package org.apache.spark.sql.sources.v2;

import org.apache.spark.annotation.Experimental;
import org.apache.spark.sql.catalog.v2.expressions.NamedReference;

@Experimental
public abstract class Filter {
  /**
   * Returns list of columns that are referenced by this filter.
   */
  abstract NamedReference[] references();

  protected NamedReference[] findReferences(Object valve) {
    if (valve instanceof Filter) {
      return ((Filter) valve).references();
    } else {
      return new NamedReference[0];
    }
  }
}