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

   1 // Copyright 2007 Google Inc. All rights reserved.
   2
   3 package com.google.appengine.api.datastore;
   4
   5 import static com.google.appengine.api.datastore.FetchOptions.Builder.withLimit;
   6 import static com.google.common.base.Preconditions.checkArgument;
   7
   8 import java.util.Iterator;
   9 import java.util.List;
  10
  11 /**
  12  * Implements PreparedQuery.
  13  *
  14  */
  15 class PreparedQueryImpl extends BasePreparedQuery {
  16   private final Query query;
  17   private final Transaction txn;
  18   private final QueryRunner queryRunner;
  19
  20   public PreparedQueryImpl(Query query, Transaction txn, QueryRunner queryRunner) {
  21     this.query = query;
  22     this.txn = txn;
  23     this.queryRunner = queryRunner;
  24
  25     checkArgument(txn == null || query.getAncestor() != null,
  26           "Only ancestor queries are allowed inside transactions.");
  27     TransactionImpl.ensureTxnActive(txn);
  28   }
  29
  30   private QueryResultIteratorImpl runQuery(FetchOptions fetchOptions) {
  31     return new QueryResultIteratorImpl(this, queryRunner.runQuery(fetchOptions, query, txn),
  32         fetchOptions, txn);
  33   }
  34
  35   @Override
  36   public List<Entity> asList(FetchOptions fetchOptions) {
  37     return new LazyList(runQuery(fetchOptions));
  38   }
  39
  40   @Override
  41   public QueryResultList<Entity> asQueryResultList(FetchOptions fetchOptions) {
  42     FetchOptions override = new FetchOptions(fetchOptions);
  43     if (override.getCompile() == null) {
  44       override.compile(true);
  45     }
  46     LazyList lazyList = new LazyList(runQuery(override));
  47     return lazyList;
  48   }
  49
  50   @Override
  51   public Iterator<Entity> asIterator(FetchOptions fetchOptions) {
  52     return runQuery(fetchOptions);
  53   }
  54
  55   @Override
  56   public QueryResultIterator<Entity> asQueryResultIterator(FetchOptions fetchOptions) {
  57     if (fetchOptions.getCompile() == null) {
  58       fetchOptions = new FetchOptions(fetchOptions).compile(true);
  59     }
  60     return runQuery(fetchOptions);
  61   }
  62
  63   @Override
  64   public Entity asSingleEntity() throws TooManyResultsException {
  65     List<Entity> entities = asList(withLimit(2));
  66     if (entities.isEmpty()) {
  67       return null;
  68     } else if (entities.size() != 1) {
  69       throw new TooManyResultsException();
  70     }
  71     return entities.get(0);
  72   }
  73
  74   @Override
  75   /**
  76    * Counts the number of entities in the result set.
  77    *
  78    * This method will run a query that will offset past all results and return
  79    * the number of results that have been skipped in the process.
  80    *
  81    * (offset, limit) is converted to (offset + limit, 0) so that no results are
  82    * actually returned. The resulting count is max(0, skipped - offset). This
  83    * is the number of entities in the range [offset, offset + limit) which is
  84    * the count.
  85    */
  86   public int countEntities(FetchOptions fetchOptions) {
  87     FetchOptions overrideOptions = new FetchOptions(fetchOptions);
  88
  89     overrideOptions.limit(0);
  90     if (fetchOptions.getLimit() != null) {
  91       if (fetchOptions.getOffset() != null) {
  92         int offset = fetchOptions.getLimit() + fetchOptions.getOffset();
  93         overrideOptions.offset(offset >= 0 ? offset : Integer.MAX_VALUE);
  94       } else {
  95         overrideOptions.offset(fetchOptions.getLimit());
  96       }
  97     } else {
  98       overrideOptions.offset(Integer.MAX_VALUE);
  99     }
 100
 101     int count = runQuery(overrideOptions).getNumSkipped();
 102     if (fetchOptions.getOffset() != null) {
 103       if (count < fetchOptions.getOffset()) {
 104         count = 0;
 105       } else {
 106         count = count - fetchOptions.getOffset();
 107       }
 108     }
 109     return count;
 110   }
 111
 112   @Override
 113   public String toString() {
 114     return query + (txn != null ? " IN " + txn : "");
 115   }
 116 }