Comunica Explain Physical Query Process Actor

An Query Process actor that explains the physical query plan after parsing, optimizing, and evaluating.

These modes execute the query, as the plan reports what actually ran, so explaining an update performs it. Operators below one that stops early, such as a LIMIT, are cut short: they report as destroyed, and how far they got can differ between runs.

Output

physical reports what ran: the logical and physical operator of every node, and the source it was handed to. physical-stats adds the measurements of each one — its estimated (cardEst) and actual (cardReal) cardinality, the time in its own output iterator (timeSelf) and the time until it ended (timeLife). Neither timing adds up to a total: nested operators overlap, and an operator that passes its input's stream through unchanged reports the same timeSelf as the one below it. physical-json reports everything, as JSON.

Operations that evaluate a sub-operation per binding, such as bind joins, EXISTS filters and arbitrary-length property paths, group those evaluations under a node of their own, in which identical sub-plans are summarized as compacted-occurrences, with their totals under physical-stats.

When a source handles an operation itself, the operations it was handed are reported below it as delegated. SPARQL endpoints also report the query they sent (srcQuery), and how many HTTP requests they made (httpRequests) once statistics are asked for. Long values are interned into legends below the plan.

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-query-process-explain-physical
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Configure

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

{
  "@context": [
    ...
    "https://linkedsoftwaredependencies.org/bundles/npm/@comunica/actor-query-process-explain-physical/^1.0.0/components/context.jsonld"
  ],
  "actors": [
    ...
    {
      "@id": "urn:comunica:default:query-process/actors#explain-physical",
      "@type": "ActorQueryProcessExplainPhysical"
    }
  ]
}
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