Re: [update] piggybank performance profiling

From: Jeen Broekstra <jeen_at_aduna.biz>
Date: Mon, 05 Sep 2005 08:35:18 +0200

Stefano Mazzocchi wrote:

> Well, it's worse than this, I suspect that while the "subj pred ?x"
> queries are hashed, the "?x pred obj" queries are iterated, meaning
> that it's not a fixed cost that we are paying but a cost that is
> proportional to the amount of data in the triple store... and this is
> *really* bad news!
>
> Jeen, are we doing something wrong? or is this really Sesame's
> limitation?

This is probably indeed a limitation of the current native store -
Arjohn can comment on this in more detail (I'll ask him about it as soon
as he checks in today) as he designed the native store's indexes, but
IIRC we limited the number and type of indexes in the native store to
speed up upload, at the cost of bad performance on some query patterns
(which were uncommon patterns in the use cases we had in mind for the
native store).

This is not insurmountable by the way. It should be doable to add an
extra index relatively quickly. I'll come back to this when I've had
more coffee and details.

FWIW: both the in-memory store and the RDBMS-backed store do not have
this limitation.

Jeen
Received on Mon Sep 05 2005 - 06:31:42 EDT