In past releases, Relations could be compressed to take up less memory. Because of improvements in the library's handling of memory, we no longer use this feature. The interface still exists to avoid breaking existing code, but the functions don't do anything.
If you find that the memory improvements are not sufficient for you, you can try re-enabling the compression features with the compiler option -DINCLUDE_COMPRESSION . Since we don't use this anymore, it is possible that code in the current release is not compatible with this option.