Re: hamsterdb Transactional Storage (thanks to all of you)

From: <compdb_at_hotmail.com>
Date: Wed, 7 Oct 2009 15:59:01 -0700 (PDT)
Message-ID: <8ec898d9-e319-4dcc-aaac-8ebf7d3342ed_at_g22g2000prf.googlegroups.com>


On Oct 5, 10:56 am, rp..._at_pcwin518.campus.tue.nl (rpost) wrote:
> >To NEST is to allow relations as attribute types.
> No, it is an operator that creates nested relations from flat relations.

Sure. So does EXTENDing by a relation attribute. I meant that if we have relation attributes we can write R NEST A using other operators. See Date & Darwen's TTM 3rd ed end of appendix A re GROUP.

> >If you have a generalized aggregate corresponding to series notation
> >you can express UNNEST as UNION over a set of tuples.

If we could define aggregates like SUM(R, X) and PRODUCT(R, X+Y) for arbitrary operators via a generalization of standard math SIGMA and PI series notation over elements of a set then we could define R UNNEST A as the iterated UNION over tuples t in R of expression (relation{t} REMOVE A) JOIN t.A. So generalized aggregates give it for free.

philip Received on Thu Oct 08 2009 - 00:59:01 CEST

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