Method getScanner

src/meta/TSUIDQuery.java:741–786

Configures the scanner for a specific metric and optional tags @return A configured scanner

()

   * @return A configured scanner
   */
  private Scanner getScanner() {
    final Scanner scanner = tsdb.getClient().newScanner(tsdb.metaTable());
    scanner.setStartKey(metric_uid);
    
    // increment the metric UID by one so we can scan all of the rows for the
    // given metric
    final long stop = UniqueId.uidToLong(metric_uid, TSDB.metrics_width()) + 1;
    scanner.setStopKey(UniqueId.longToUID(stop, TSDB.metrics_width()));
    scanner.setFamily(TSMeta.FAMILY());
    
    // set the filter if we have tags
    if (!tags.isEmpty()) {
      final short name_width = TSDB.tagk_width();
      final short value_width = TSDB.tagv_width();
      final short tagsize = (short) (name_width + value_width);
      // Generate a regexp for our tags.  Say we have 2 tags: { 0 0 1 0 0 2 }
      // and { 4 5 6 9 8 7 }, the regexp will be:
      // "^.{7}(?:.{6})*\\Q\000\000\001\000\000\002\\E(?:.{6})*\\Q\004\005\006\011\010\007\\E(?:.{6})*$"
      final StringBuilder buf = new StringBuilder(
          15  // "^.{N}" + "(?:.{M})*" + "$"
          + ((13 + tagsize) // "(?:.{M})*\\Q" + tagsize bytes + "\\E"
             * (tags.size())));

      // Alright, let's build this regexp.  From the beginning...
      buf.append("(?s)"  // Ensure we use the DOTALL flag.
                 + "^.{")
         // ... start by skipping the metric ID.
         .append(TSDB.metrics_width())
         .append("}");
      final Iterator<byte[]> tags = this.tag_uids.iterator();
      byte[] tag = tags.hasNext() ? tags.next() : null;
      // Tags and group_bys are already sorted.  We need to put them in the
      // regexp in order by ID, which means we just merge two sorted lists.
      do {
        // Skip any number of tags.
        buf.append("(?:.{").append(tagsize).append("})*\\Q");
        UniqueId.addIdToRegexp(buf, tag);
        tag = tags.hasNext() ? tags.next() : null;
      } while (tag != null);  // Stop when they both become null.
      // Skip any number of tags before the end.
      buf.append("(?:.{").append(tagsize).append("})*$");
      scanner.setKeyRegexp(buf.toString(), CHARSET);
    }
    
    return scanner;
  }
}