java/src/main/com/google/appengine/api/search/Consistency.java

   1 // Copyright 2010 Google Inc. All Rights Reserved.
   2 package com.google.appengine.api.search;
   3
   4 /**
   5  * Supported consistency modes by indexes. When creating an index you may
   6  * request whether the index is {@link #GLOBAL} or {@link #PER_DOCUMENT}
   7  * consistent using this enum. An index with {@link #GLOBAL} consistency, when
   8  * searched, returns results with all changes prior to the search request,
   9  * committed. For {@link #PER_DOCUMENT} consistent indexes, a search result may
  10  * contain some out of date documents. However, any two changes to any document
  11  * stored in such an index are applied in the correct order. The benefit of
  12  * {@link #PER_DOCUMENT} consistent index is that it provides much higher index
  13  * document throughput than a globally consistent one.
  14  *
  15  * <p>Typically, you would use {@link #GLOBAL} consistency if organizing
  16  * personal user information, to reflect all changes known to the user in
  17  * any search results. The {@link #PER_DOCUMENT} consistency should be used
  18  * in indexes that amalgamate information from multiple sources, where no
  19  * single user is aware of all collected data.
  20  *
  21  */
  22 public enum Consistency {
  23   /**
  24    * Globally consistent index, which guarantees that search returns
  25    * results including changes submitted before the latest search request.
  26    */
  27   GLOBAL(SearchServicePb.IndexSpec.Consistency.GLOBAL),
  28
  29   /**
  30    * Document level consistent index, with search results that may not include
  31    * the latest changes to the index.
  32    */
  33   PER_DOCUMENT(SearchServicePb.IndexSpec.Consistency.PER_DOCUMENT);
  34
  35   private final SearchServicePb.IndexSpec.Consistency consistency;
  36
  37   private Consistency(SearchServicePb.IndexSpec.Consistency consistency) {
  38     this.consistency = consistency;
  39   }
  40
  41   SearchServicePb.IndexSpec.Consistency getConsistency() {
  42     return consistency;
  43   }
  44
  45   static Consistency fromProto(SearchServicePb.IndexSpec.Consistency consistency) {
  46     return consistency.equals(SearchServicePb.IndexSpec.Consistency.GLOBAL)
  47         ? GLOBAL : PER_DOCUMENT;
  48   }
  49 }