FROM / FROM NAMED create a dynamic dataset for TDB which id a subset of
all graphs.
https://jena.apache.org/documentation/tdb/dynamic_datasets.html
The for this is in org.apache.jena.sparql.core.DyanmicDatasets
Andy
On 11/09/17 13:40, George News wrote:
On 2017-09-08 20:18, Andy Seaborne wrote:
Yes, Chris - MultiUnion is linking with a distinguished that is updated.
(Changing that would be a BIG change!)
Datasets like TIM (transactions in memory) and TDB can provide the union
graph of their named graphs and more efficiently than the general purpose
MultiUnion.
Previously I was using the "urn:x-arq:UnionGraph" named graph, but now I
need to be less generic and only include some of them. This is why I
have to work with the other options :(
Andy
On 8 September 2017 at 13:52, Chris Dollin <[email protected]>
wrote:
On 8 September 2017 at 10:11, George News <[email protected]> wrote:
Hi,
Is multiunion only linking the graphs or copying them in a new graph?
I'm thinking on splitting a huge graph on many simple ones and them
making the union depending on the part of the main graph that has to be
requested, therefore limiting the scope of the sparql and speeding
things up. But if multiunion copies, then I don't think I will speed
things.
If things haven't changed too much ...
(a) it links the graphs. They are not copied. Hooray!
(b)ut when you run an operation over the graph that delivers
a set of triples (which is how queries work over union graphs)
it has to remember all the triples it has already seen so that it
doesn't deliver duplicates. Hence (depending on the triple
pattern being used) may mean lots of store being held onto.
Alas!
Chris
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