On 07/26/2013 12:51 PM, Andy Seaborne wrote:
Not silly - with federated query there isn't enough information available for an optimizer to make sensible choices, and, worse, it's an area where ordering of operations is much more noticeable (the operations are inherently more expensive). In practice, I think you have to give the query writer control.
I was thinking about this recently but didn't get a chance to fully investigate this:
Making stats.opt data available to consumers. This is perhaps an implementation or a nice practice but it could be very useful if not already done. In http://csarven.ca/linked-statistical-data-analysis I mentioned that stats.opt incorporated in VoID along with LODStats can help applications to devise better performing federated queries.
I'm not entirely familiar with this, but federated query extensions e.g., DARQ, may have employed something like this?
-Sarven
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