message: Reduce RAM usage
diff: @@ -712,7 +712,7 @@ mod tests {
  {
  // writing the segment
  - let mut index_writer = index.writer_with_num_threads(3, 40_000_000).unwrap();
  + let mut index_writer = index.writer_with_num_threads(3, 3_000_000).unwrap();
  index_writer.add_document(doc!(text_field=>"a"));
  index_writer.rollback().unwrap();
  @@ -745,7 +745,7 @@ mod tests {
  };
  {
  // writing the segment
  - let mut index_writer = index.writer_with_num_threads(4, 4 * 30_000_000).unwrap();
  + let mut index_writer = index.writer_with_num_threads(4, 3_000_000).unwrap();
  // create 8 segments with 100 tiny docs
  for _doc in 0..100 {
  let mut doc = Document::default();
  @@ -779,7 +779,7 @@ mod tests {
  {
  // writing the segment
  - let mut index_writer = index.writer_with_num_threads(4, 4 * 30_000_000).unwrap();
  + let mut index_writer = index.writer_with_num_threads(4, 3_000_000).unwrap();
  // create 8 segments with 100 tiny docs
  for _doc in 0..100 {
  index_writer.add_document(doc!(text_field => "a"));
  @@ -814,7 +814,7 @@ mod tests {
  {
  // writing the segment
  - let mut index_writer = index.writer_with_num_threads(4, 4 * 30_000_000).unwrap();
  + let mut index_writer = index.writer_with_num_threads(4, 3_000_000).unwrap();
  // create 8 segments with 100 tiny docs
  for _doc in 0..100 {
  index_writer.add_document(doc!(text_field => "a"));
  