You might want to look at the following bits of code then:
* https://github.com/apache/jena/blob/main/jena-arq/src/main/java/org/apache/jena/sparql/engine/optimizer/StatsMatcher.java - The code that uses pre-computed statistics, plus some weighting factors to decide how to reorder triple/quad patterns within BGPs * https://github.com/apache/jena/blob/main/jena-arq/src/main/java/org/apache/jena/sparql/algebra/optimize/TransformReorder.java - An algebra transform that reorders the triple/quad patterns within BGPs. Jena has both a statistics and a non-statistics based reordering available. * https://github.com/apache/jena/blob/main/jena-cmds/src/main/java/tdb/tdbstats.java - A command line utility that pre-computes cardinality statistics for TDB databases Rob From: Hashim Khan <engr.hashimwa...@gmail.com> Date: Tuesday, 12 April 2022 at 16:13 To: users@jena.apache.org <users@jena.apache.org> Subject: Re: cardinality estimation HI, I just want to see how cardinality estimation can be done programmatically. whatever query or dataset it may be, but I want to see it practically. On Tue, Apr 12, 2022 at 4:33 PM rve...@dotnetrdf.org <rve...@dotnetrdf.org> wrote: > Hi > > Could you provide more detail about what you are after? The amount of > triples that are scanned for a given SPARQL query can vary widely both > based on the query and how that query gets optimised (which can be data > dependent) > > I don’t think there is anything specifically exposed in the Jena APIs for > this > > Rob > > From: Hashim Khan <engr.hashimwa...@gmail.com> > Date: Tuesday, 12 April 2022 at 14:02 > To: users@jena.apache.org <users@jena.apache.org> > Subject: cardinality estimation > Hi, > I would like to ask about any specific class or method in Jana which > can return a value showing the estimated number of triples for a SPARQL > query? > > > Regards > -- > *Hashim Khan* > -- *Hashim Khan*
