java/src/main/com/google/appengine/api/datastore/IndexComponent.java

   1 // Copyright 2012 Google Inc. All Rights Reserved.
   2
   3 package com.google.appengine.api.datastore;
   4
   5 import com.google.storage.onestore.v3.OnestoreEntity.Index.Property;
   6
   7 import java.util.List;
   8
   9 /**
  10  * An interface that represents a collection of index constraints. It can validate
  11  * if an index satisfies the constraints.
  12  *
  13  */
  14 interface IndexComponent {
  15
  16   /**
  17    * Given a list of index {@link Property}s, returns true if the index matches the
  18    * constraints given by the {@link IndexComponent}.
  19    *
  20    * @param indexProperties the index properties to match against
  21    * @return true if the index satisfies the component
  22    */
  23  boolean matches(List<Property> indexProperties);
  24
  25   /**
  26    * Returns the list of {@link Property}s that best satisfy this index component.
  27    */
  28  List<Property> preferredIndexProperties();
  29
  30  /**
  31   * Returns the number of index constraints in this component.
  32   *
  33   * If a {@code List<Property>} satisfies this {@link IndexComponent}, and thus
  34   * {@link IndexComponent#matches} returns true, the number of properties
  35   * satisfied will be equal to the size of the {@link IndexComponent}.
  36   *
  37   * @return the number of index constraints.
  38   */
  39   int size();
  40 }