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Elastic Docs ›Elasticsearch Guide [6.8] ›Query DSL

Query and filter context

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Query and filter context

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The behaviour of a query clause depends on whether it is used in query context or in filter context:

Query context

A query clause used in query context answers the question “How well does this document match this query clause?” Besides deciding whether or not the document matches, the query clause also calculates a _score representing how well the document matches, relative to other documents.

Query context is in effect whenever a query clause is passed to a query parameter, such as the query parameter in the search API.

Filter context

In filter context, a query clause answers the question “Does this document match this query clause?” The answer is a simple Yes or No — no scores are calculated. Filter context is mostly used for filtering structured data, e.g.

  • Does this timestamp fall into the range 2015 to 2016?
  • Is the status field set to "published"?

Frequently used filters will be cached automatically by Elasticsearch, to speed up performance.

Filter context is in effect whenever a query clause is passed to a filter parameter, such as the filter or must_not parameters in the bool query, the filter parameter in the constant_score query, or the filter aggregation.

Below is an example of query clauses being used in query and filter context in the search API. This query will match documents where all of the following conditions are met:

  • The title field contains the word search.
  • The content field contains the word elasticsearch.
  • The status field contains the exact word published.
  • The publish_date field contains a date from 1 Jan 2015 onwards. 
GET /_search
{
  "query": { 
    "bool": { 
      "must": [
        { "match": { "title":   "Search"        }},
        { "match": { "content": "Elasticsearch" }}
      ],
      "filter": [ 
        { "term":  { "status": "published" }},
        { "range": { "publish_date": { "gte": "2015-01-01" }}}
      ]
    }
  }
}

The query parameter indicates query context.

The bool and two match clauses are used in query context, which means that they are used to score how well each document matches.

The filter parameter indicates filter context. Its term and range clauses are used in filter context. They will filter out documents which do not match, but they will not affect the score for matching documents.

Scores calculated for queries in query context are represented as single precision floating point numbers; they have only 24 bits for significand’s precision. Score calculations that exceed the significand’s precision will be converted to floats with loss of precision.

Use query clauses in query context for conditions which should affect the score of matching documents (i.e. how well does the document match), and use all other query clauses in filter context.

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