Method buildFuzzyFilters

src/query/QueryUtil.java:280–383

Crafts a list of FuzzyFilters for scanning over data table rows and filtering time series that the user doesn't want. Note: The caller has to restrict the scan to proper start and stop for the filter to work correctly. @param row_key_literals A list of key value pairs to filter on. @param fuzzy_key

(
      final ByteMap<byte[][]> row_key_literals,
      final byte[] fuzzy_key)

   * @return A sorted, non-empty list of FuzzyFilterPair
   */
  private static List<FuzzyFilterPair> buildFuzzyFilters(
      final ByteMap<byte[][]> row_key_literals,
      final byte[] fuzzy_key) {
    final int prefix_width = Const.SALT_WIDTH() + TSDB.metrics_width() + 
        Const.TIMESTAMP_BYTES;
    final short name_width = TSDB.tagk_width();
    final short value_width = TSDB.tagv_width();
    final short tag_width = (short) (name_width + value_width);
    int row_key_size = prefix_width;
    if (row_key_literals != null) {
      for(byte[][] v: row_key_literals.values()) {
        final boolean not_key = v!=null && v.length==0;
        if (!not_key) {
          row_key_size += tag_width;
        }
      }
    }
    final List<FuzzyFilterPair> fuzzy_filter_pairs =
        new ArrayList<FuzzyFilterPair>(row_key_literals.size());
    
    // Initialize first_fuzzy_key and first_fuzzy_mask
    // these will serve as model for the fuzzy filter list
    // generated for tags with multiple values (|)
    byte[] first_fuzzy_key  = Arrays.copyOf(fuzzy_key, fuzzy_key.length);
    byte[] first_fuzzy_mask = new byte[fuzzy_key.length];
    int fuzzy_offset = 0;
    
    // TODO - see if it's less expensive to skip the salt, timestamp and metric.
    // skip salt & timestamp (filtering should be done by start/stop
    // of the scanner)
    while(fuzzy_offset < prefix_width) {
      first_fuzzy_key[fuzzy_offset] = 0;
      first_fuzzy_mask[fuzzy_offset++] = 
          (row_key_literals != null) ? (byte)1 : (byte)0; 
    }
    
    // first pass to build the key and mask
    Iterator<Entry<byte[], byte[][]>> it = row_key_literals.iterator();
    while(it.hasNext()) {
      Entry<byte[], byte[][]> entry = it.next();
      final boolean not_key = 
          entry.getValue() != null && entry.getValue().length == 0;

      if (!not_key) {
        final byte[] tag_key = entry.getKey();
        System.arraycopy(tag_key, 0, 
            first_fuzzy_key, fuzzy_offset, name_width);
        for (int i=0; i<name_width; i++) {
          first_fuzzy_mask[fuzzy_offset++] = 0; 
        }

        final byte[] tag_value;
        if (entry.getValue()!=null && entry.getValue().length > 0) {
          tag_value = entry.getValue()[0];
        } else {
          tag_value = null;
        }