anchor.diff:  -define(VALUES_COMPRESS_LEVEL(W), W#writer.segment_values_compression_level).
   -define(INDEX_FIELD_TERM(X), {element(1, X), element(2, X), element(3, X)}).
   -define(VALUE(X), element(4, X)).
  --define(VALUE_PROPS_TSTAMP(X), {element(4, X), element(5, X), element(6, X)}).
  +-define(VALUE_TSTAMP_PROPS(X), {element(4, X), element(5, X), element(6, X)}).
   
   -record(writer, {data_file,
                    offsets_table,
  
positive.code:     %% Start a new term.
      W1 = from_iterator_process_end_term(StartIFT, W),
      W2 = from_iterator_process_start_term(?INDEX_FIELD_TERM(Entry), W1),
      W3 = from_iterator_process_value(?VALUE_PROPS_TSTAMP(Entry), W2),
      from_iterator(Iterator(), ?INDEX_FIELD_TERM(Entry), ?VALUE(Entry), W3);
  
  from_iterator({Entry, Iterator}, StartIFT, LastValue, W) 
  
negative.code:   when ?INDEX_FIELD_TERM(Entry) == StartIFT andalso
         ?VALUE(Entry) /= LastValue ->
      %% Add the next value to the segment.
      W1 = from_iterator_process_value(?VALUE_TSTAMP_PROPS(Entry), W),
      from_iterator(Iterator(), StartIFT, ?VALUE(Entry), W1);
  
  from_iterator({Entry, Iterator}, StartIFT, _LastValue, W) 
  