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  package org.apache.cayenne.ejbql;
  
  import java.util.List;
  
  import org.apache.cayenne.map.DbRelationship;
  import org.apache.cayenne.map.SQLResult;
  import org.apache.cayenne.query.PrefetchTreeNode;
  import org.apache.cayenne.reflect.ClassDescriptor;
  
  /**
   * Represents an EJB QL expression "compiled" in the context of a certain mapping.
   * 
   * @since 3.0
   */
  public interface EJBQLCompiledExpression {
  
      /**
       * Returns a tree representation of an EJBQL expression.
       */
      EJBQLExpression getExpression();
  
      /**
       * Returns a descriptor of the root of this expression such as entity being fetched or
       * updated.
       */
      ClassDescriptor getRootDescriptor();
  
      /**
       * Returns a ClassDescriptor for the id variable.
       */
      ClassDescriptor getEntityDescriptor(String identifier);
  
      /**
       * Returns a collection of relationships that joins identifier with a parent entity.
       * Returns null if the identifier corresponds to one of the query roots.
       */
      List<DbRelationship> getIncomingRelationships(String identifier);
  
      /**
       * Returns EJB QL source of the compiled expression if available.
       */
      String getSource();
  
      /**
       * Returns a mapping of the result set columns, or null if this is not a select
       * expression.
       */
      SQLResult getResult();
      
      /**
       * Returns prefetched columns tree for fetch joins.
       */
      PrefetchTreeNode getPrefetchTree();
  }
  