ceph/src/rocksdb/java/src/main/java/org/rocksdb/BloomFilter.java

   1 // Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
   2 // This source code is licensed under the BSD-style license found in the
   3 // LICENSE file in the root directory of this source tree. An additional grant
   4 // of patent rights can be found in the PATENTS file in the same directory.
   5
   6 package org.rocksdb;
   7
   8 /**
   9  * Bloom filter policy that uses a bloom filter with approximately
  10  * the specified number of bits per key.
  11  *
  12  * <p>
  13  * Note: if you are using a custom comparator that ignores some parts
  14  * of the keys being compared, you must not use this {@code BloomFilter}
  15  * and must provide your own FilterPolicy that also ignores the
  16  * corresponding parts of the keys. For example, if the comparator
  17  * ignores trailing spaces, it would be incorrect to use a
  18  * FilterPolicy (like {@code BloomFilter}) that does not ignore
  19  * trailing spaces in keys.</p>
  20  */
  21 public class BloomFilter extends Filter {
  22
  23   private static final int DEFAULT_BITS_PER_KEY = 10;
  24   private static final boolean DEFAULT_MODE = true;
  25
  26   /**
  27    * BloomFilter constructor
  28    *
  29    * <p>
  30    * Callers must delete the result after any database that is using the
  31    * result has been closed.</p>
  32    */
  33   public BloomFilter() {
  34     this(DEFAULT_BITS_PER_KEY, DEFAULT_MODE);
  35   }
  36
  37   /**
  38    * BloomFilter constructor
  39    *
  40    * <p>
  41    * bits_per_key: bits per key in bloom filter. A good value for bits_per_key
  42    * is 10, which yields a filter with ~ 1% false positive rate.
  43    * </p>
  44    * <p>
  45    * Callers must delete the result after any database that is using the
  46    * result has been closed.</p>
  47    *
  48    * @param bitsPerKey number of bits to use
  49    */
  50   public BloomFilter(final int bitsPerKey) {
  51     this(bitsPerKey, DEFAULT_MODE);
  52   }
  53
  54   /**
  55    * BloomFilter constructor
  56    *
  57    * <p>
  58    * bits_per_key: bits per key in bloom filter. A good value for bits_per_key
  59    * is 10, which yields a filter with ~ 1% false positive rate.
  60    * <p><strong>default bits_per_key</strong>: 10</p>
  61    *
  62    * <p>use_block_based_builder: use block based filter rather than full filter.
  63    * If you want to builder full filter, it needs to be set to false.
  64    * </p>
  65    * <p><strong>default mode: block based filter</strong></p>
  66    * <p>
  67    * Callers must delete the result after any database that is using the
  68    * result has been closed.</p>
  69    *
  70    * @param bitsPerKey number of bits to use
  71    * @param useBlockBasedMode use block based mode or full filter mode
  72    */
  73   public BloomFilter(final int bitsPerKey, final boolean useBlockBasedMode) {
  74     super(createNewBloomFilter(bitsPerKey, useBlockBasedMode));
  75   }
  76
  77   private native static long createNewBloomFilter(final int bitsKeyKey,
  78       final boolean useBlockBasedMode);
  79 }