Thanks Hugh,
We don't have a problem with this but I'm a bit ignorant when it comes to
the sql implications of some sparql constructs and I wanted to get some
idea of the potential pitfalls.
It sounds like the construct I was intending is potentially problematic
right now but will be fine in the future. So I guess I just implement it
as written and it will work itself out.
On 20 December 2013 01:00, Hugh Williams <hwilli...@openlinksw.com> wrote:
> Hi Quentin,
>
> Development indicate that the correct way is using an "INI" clause ie "?g
> in (<g1>, >G2>, …)" , as this does not make temporary tables. The problem
> you are getting is that you get one indexed access per distinct g because g
> is a key part of the rdf quad table, which is due to a bad query plan.
> There is an update already done and pending inclusion into open source that
> does the "IN" clause as an invisible hash join, i.e. hash join merged into
> index lookup and is one of the fastest on the block, including all the
> specialized column store data warehouses. With the update the not in case
> is also very efficient. If obtain a query plan with the "explain" or
> "profile" functions and you see an "in_iter" on the g in front of an access
> to rdf_quad in the plan explain then you have the wrong thing. If you have
> the rdf quad first and then hash partition+bloom than it is the good one.
>
> Best Regards
> Hugh Williams
> Professional Services
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> On 13 Dec 2013, at 06:43, Quentin <quent...@clearbluewater.com.au> wrote:
>
> > Hi,
> >
> > If I'm executing a query in sparql, in Virtuoso 7, that uses heavy graph
> filtering along the lines of:
> >
> > SELECT *
> > { GRAPH ?G {
> > filter ( ?G in (<test1>, <test2>....<test76>) )
> > ....
> > }}
> >
> > Will this cause large temporary tables to be created or will it just do
> lookups against the Graph column of the Quad store?
> >
> > If the above is a bad idea, is there a more efficient way to join or
> filter graphs?
> >
> > A secondary question is would this query be rendered much more expensive
> if it included a subclause along the lines of:
> > SELECT *
> > { GRAPH ?G {
> > filter ( ?G in (<test1>, <test2>....<test76>) )
> > { GRAPH ?Ginner {
> > filter (?Ginner in ( <test11>,<test13>,<test17> ) )
> > }}}}
> >
> > Does this type of construction force temporary tables?
> > --
> > Quentin | Clear Blue Water Pty Ltd
> > quent...@clearbluewater.com.au
> >
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--
Quentin | Clear Blue Water Pty Ltd
quent...@clearbluewater.com.au
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