Hi @hyoklee,
AFAWK, the post you have shared refers to indexing HDF5 (meta)data to speed-up filtering data according to user-defined criteria afterwards. What we are envisioning for HDFql is to only index the structure of the HDF5 file (i.e. the names of (nested) objects and their organization within the file) though - this should satisfy the original issue (i.e. lack of performance when trying to identify a group amongst thousands of datasets) raised by @torbjorns.
It seems that what is presented/discussed in this post has some kind of overlap with MIQS and, eventually, also with HDF5 H5Q/H5X APIs. It would be great if all these disparate efforts could be federated into one single approach/solution - this would greatly benefit the HDF5 community at large.
That said, we also see an overlap between what we envision and HDF5 H5Q/H5X APIs but only the part that touches HDF5 structure. Indexing the structure of an HDF5 file should be easier to implement (when compared with indexing HDF5 (meta)data) and, hopefully, feasible before 2036 
Hope it helps!