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

   1 // Copyright 2012 Google Inc. All Rights Reserved.
   2
   3 package com.google.appengine.api.datastore;
   4
   5 import com.google.common.collect.Lists;
   6 import com.google.common.collect.Sets;
   7 import com.google.storage.onestore.v3.OnestoreEntity.Index.Property;
   8 import com.google.storage.onestore.v3.OnestoreEntity.Index.Property.Direction;
   9
  10 import java.util.List;
  11 import java.util.ListIterator;
  12 import java.util.Set;
  13 import java.util.SortedSet;
  14
  15 /**
  16  * Implements an {@link IndexComponent} that is unordered.
  17  *
  18  * This is currently used for exists and group by filters.
  19  *
  20  */
  21 class UnorderedIndexComponent implements IndexComponent {
  22
  23   private final SortedSet<String> matcherProperties;
  24
  25   public UnorderedIndexComponent(Set<String> unorderedGroup) {
  26     this.matcherProperties = Sets.newTreeSet(unorderedGroup);
  27   }
  28
  29   @Override
  30   public boolean matches(List<Property> indexProperties) {
  31     Set<String> unorderedProps = Sets.newHashSet(matcherProperties);
  32     ListIterator<Property> indexItr = indexProperties.listIterator(indexProperties.size());
  33     while (!unorderedProps.isEmpty() && indexItr.hasPrevious()) {
  34       if (!unorderedProps.remove(indexItr.previous().getName())) {
  35         return false;
  36       }
  37     }
  38     return unorderedProps.isEmpty();
  39   }
  40
  41   @Override
  42   public List<Property> preferredIndexProperties() {
  43     List<Property> indexProps = Lists.newArrayListWithExpectedSize(matcherProperties.size());
  44     for (String name : matcherProperties) {
  45       Property indexProperty = new Property();
  46       indexProperty.setName(name);
  47       indexProperty.setDirection(Direction.ASCENDING);
  48       indexProps.add(indexProperty);
  49     }
  50     return indexProps;
  51   }
  52
  53   @Override
  54   public int size() {
  55     return matcherProperties.size();
  56   }
  57
  58   @Override
  59   public String toString() {
  60     return "UnorderedIndexComponent: " + matcherProperties;
  61   }
  62 }