@comunica/mediator-combine-union

Comunica Mediator Combine Union

A comunica mediator that takes the union of all actor results.

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/mediator-combine-union

Configure

After installing, this mediator can be instantiated as follows:

{
  "@context": [
    ...
    "https://linkedsoftwaredependencies.org/bundles/npm/@comunica/mediator-combine-union/^3.0.0/components/context.jsonld"
  ],
  "actors": [
    ...
    {
      "@type": "SomeActor",
      "someMediator": {
        "@id": "#mediatorRdfParseMediatypes",
        "@type": "MediatorCombineUnion",
        "bus": { "@id": "ActorRdfParse:_default_bus" },
        "field": "mediaTypes"
      }
    }
  ]
}

Config Parameters

• bus: Identifier of the bus to mediate over.
• field: The field name to mediate over.
• filterErrors: Optional flag to indicate if actors that throw test errors should be filtered out of the pipeline, defaults to false.

Changelog

v3.2.1 - 2024-08-07

Added

• Add support for deduplication of results in construct queries

Changed

• Remove projection variables missing warning
• Migrate parse-link-header to http-link-header
• Migrate stream-to-string and streamify-string
• Performance improvements:
  • Tweak default BindJoin.minMaxCardinalityRatio value for WatDiv-C1
  • Use Bind Join only if smallest much smaller than largest
  • Assign smallest stream as build side in Hash Join, #884
  • Force NLJ when join entries have no overlapping variables

Fixed

• Fix optimizer incorrectly considering some optionals empty
• Fix SLICE actor not working with ASK queries, Closes #1374
• Make projection variables missing error a warning instead
• Fix some unions in federated queries being pruned incorrectly, Closes #1397
• Avoid single-entry joins in join-connected optimizer, #1397
• Consider unions when determining if operation can produce undefs, #1406
• Fix undefined values from SPARQL endpoints being produced
• Fix unnecessary join being created when binding over filter
• Fix initialBindings failing when done over projected variables

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