HDT does actually create more indices "out of band", that it they create a separate file.hdt.index files. The combined size however is still much smaller than a TDB store of the same file, but I don't know if this is down to TDB simply having more indices.
Sent: Sunday, November 26, 2017 at 5:20 PM From: ajs6f <[email protected]> To: [email protected] Subject: Re: Estimating TDB2 size You have to start with the understanding that the indexes in a database are not the same thing nor for the same purpose as a simple file of triples or quads. TDB1 and 2 store the same triple several times in different orders (SPO, OPS, etc.) in order to be able to answer arbitrary queries with good performance, which is a common technique. There is no reason to expect a database that is capable of answering arbitrary queries with good performance to be as small as a file, which is not. ajs6f
