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Elite Set Operator

Picks the best N subqueries and combine them with _or.

If you want to find documents similar to a piece of text, an obvious approach is to build an _or query from all the terms in the text, and run this query against a database containing the documents. However such a query can contain lots of terms and be quite slow to perform, yet many of these terms don’t contribute usefully to the results.

The _elite_set operator can be used instead of _or in this situation. _elite_set selects the most important N terms and then acts as an _or query with just these, ignoring any other terms. This will usually return results just as good as the full _or query, but much faster.

In general, the _elite_set operator can be used when you have a large OR query, but it doesn’t matter if the search completely ignores some of the less important terms in the query.

The subqueries don’t have to be terms, but if they aren’t then _elite_set will look at the estimated frequencies of the subqueries and so could pick a subset which don’t actually match any documents even if the full OR would match some.

You can specify a parameter to the query constructor which control the number of terms which _elite_set will pick. If not specified, this defaults to 10.

If the number of subqueries is less than this threshold, _elite_set behaves identically to _or.

SEARCH /bank/
{
  "_query": {
    "_elite_set": [
      { "personality": "biggest" },
      { "personality": "things" },
      { "personality": "lovable" },
      { "personality": "cooperative" },
      { "personality": "course" },
      { "personality": "also" },
      { "personality": "kind" },
      { "personality": "honest" },
      { "personality": "considerate" },
      { "personality": "prominent" },
      { "personality": "especially" },
      { "personality": "compared" },
      { "personality": "impulses" },
      { "personality": "shallow" },
      { "personality": "well" }
    ]
  }
}

A similar result can be achieved by setting the default operator via the Elite Set Modifier.

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