Comunica Variable Counting RDF Join Selectivity Actor

An RDF Join Selectivity actor that heuristically tries to estimate the selectivity of joins by counting the overlap of variables and non-variables in patterns.

Based on the "variable counting predicates" heuristic from Stocker, Markus, et al. "SPARQL basic graph pattern optimization using selectivity estimation." Proceedings of the 17th international conference on World Wide Web. 2008.. Implementation inspired by http://www.docjar.com/docs/api/com/hp/hpl/jena/sparql/engine/optimizer/heuristic/VariableCountingUnbound.html. This algorithm is extended to also support non-triple-pattern operations and quads.

This module is part of the Comunica framework, and should only be used by developers that want to build their own query engine.

Click here if you just want to query with Comunica.

Install

$ yarn add @comunica/actor-rdf-join-selectivity-variable-counting

Configure

After installing, this package can be added to your engine's configuration as follows:

{
  "@context": [
    ...
    "https://linkedsoftwaredependencies.org/bundles/npm/@comunica/actor-rdf-join-selectivity-variable-counting/^3.0.0/components/context.jsonld"
  ],
  "actors": [
    ...
    {
      "@id": "urn:comunica:default:rdf-join-selectivity/actors#variable-counting",
      "@type": "ActorRdfJoinSelectivityVariableCounting"
    }
  ]
}