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Search Template

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Search Template

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The /_search/template endpoint allows to use the mustache language to pre render search requests, before they are executed and fill existing templates with template parameters.

GET _search/template
{
    "source" : {
      "query": { "match" : { "{{my_field}}" : "{{my_value}}" } },
      "size" : "{{my_size}}"
    },
    "params" : {
        "my_field" : "message",
        "my_value" : "some message",
        "my_size" : 5
    }
}

For more information on how Mustache templating and what kind of templating you can do with it check out the online documentation of the mustache project.

The mustache language is implemented in Elasticsearch as a sandboxed scripting language, hence it obeys settings that may be used to enable or disable scripts per type and context as described in the scripting docs

More template examples

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Filling in a query string with a single value

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GET _search/template
{
    "source": {
        "query": {
            "term": {
                "message": "{{query_string}}"
            }
        }
    },
    "params": {
        "query_string": "search for these words"
    }
}

Converting parameters to JSON

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The {{#toJson}}parameter{{/toJson}} function can be used to convert parameters like maps and array to their JSON representation:

GET _search/template
{
  "source": "{ \"query\": { \"terms\": {{#toJson}}statuses{{/toJson}} }}",
  "params": {
    "statuses" : {
        "status": [ "pending", "published" ]
    }
  }
}

which is rendered as:

{
  "query": {
    "terms": {
      "status": [
        "pending",
        "published"
      ]
    }
  }
}

A more complex example substitutes an array of JSON objects:

GET _search/template
{
    "source": "{\"query\":{\"bool\":{\"must\": {{#toJson}}clauses{{/toJson}} }}}",
    "params": {
        "clauses": [
            { "term": { "user" : "foo" } },
            { "term": { "user" : "bar" } }
        ]
   }
}

which is rendered as:

{
    "query" : {
      "bool" : {
        "must" : [
          {
            "term" : {
                "user" : "foo"
            }
          },
          {
            "term" : {
                "user" : "bar"
            }
          }
        ]
      }
    }
}

Concatenating array of values

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The {{#join}}array{{/join}} function can be used to concatenate the values of an array as a comma delimited string:

GET _search/template
{
  "source": {
    "query": {
      "match": {
        "emails": "{{#join}}emails{{/join}}"
      }
    }
  },
  "params": {
    "emails": [ "username@email.com", "lastname@email.com" ]
  }
}

which is rendered as:

{
    "query" : {
        "match" : {
            "emails" : "username@email.com,lastname@email.com"
        }
    }
}

The function also accepts a custom delimiter:

GET _search/template
{
  "source": {
    "query": {
      "range": {
        "born": {
            "gte"   : "{{date.min}}",
            "lte"   : "{{date.max}}",
            "format": "{{#join delimiter='||'}}date.formats{{/join delimiter='||'}}"
	    }
      }
    }
  },
  "params": {
    "date": {
        "min": "2016",
        "max": "31/12/2017",
        "formats": ["dd/MM/yyyy", "yyyy"]
    }
  }
}

which is rendered as:

{
    "query" : {
      "range" : {
        "born" : {
          "gte" : "2016",
          "lte" : "31/12/2017",
          "format" : "dd/MM/yyyy||yyyy"
        }
      }
    }
}

Default values

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A default value is written as {{var}}{{^var}}default{{/var}} for instance:

{
  "source": {
    "query": {
      "range": {
        "line_no": {
          "gte": "{{start}}",
          "lte": "{{end}}{{^end}}20{{/end}}"
        }
      }
    }
  },
  "params": { ... }
}

When params is { "start": 10, "end": 15 } this query would be rendered as:

{
    "range": {
        "line_no": {
            "gte": "10",
            "lte": "15"
        }
  }
}

But when params is { "start": 10 } this query would use the default value for end:

{
    "range": {
        "line_no": {
            "gte": "10",
            "lte": "20"
        }
    }
}

Conditional clauses

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Conditional clauses cannot be expressed using the JSON form of the template. Instead, the template must be passed as a string. For instance, let’s say we wanted to run a match query on the line field, and optionally wanted to filter by line numbers, where start and end are optional.

The params would look like:

{
    "params": {
        "text":      "words to search for",
        "line_no": { 
            "start": 10, 
            "end":   20  
        }
    }
}

All three of these elements are optional.

We could write the query as:

{
  "query": {
    "bool": {
      "must": {
        "match": {
          "line": "{{text}}" 
        }
      },
      "filter": {
        {{#line_no}} 
          "range": {
            "line_no": {
              {{#start}} 
                "gte": "{{start}}" 
                {{#end}},{{/end}} 
              {{/start}} 
              {{#end}} 
                "lte": "{{end}}" 
              {{/end}} 
            }
          }
        {{/line_no}} 
      }
    }
  }
}

	Fill in the value of param `text`
	Include the `range` filter only if `line_no` is specified
	Include the `gte` clause only if `line_no.start` is specified
	Fill in the value of param `line_no.start`
	Add a comma after the `gte` clause only if `line_no.start` AND `line_no.end` are specified
	Include the `lte` clause only if `line_no.end` is specified
	Fill in the value of param `line_no.end`

As written above, this template is not valid JSON because it includes the section markers like {{#line_no}}. For this reason, the template should either be stored in a file (see Pre-registered template) or, when used via the REST API, should be written as a string:

"source": "{\"query\":{\"bool\":{\"must\":{\"match\":{\"line\":\"{{text}}\"}},\"filter\":{{{#line_no}}\"range\":{\"line_no\":{{{#start}}\"gte\":\"{{start}}\"{{#end}},{{/end}}{{/start}}{{#end}}\"lte\":\"{{end}}\"{{/end}}}}{{/line_no}}}}}}"

Encoding URLs

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The {{#url}}value{{/url}} function can be used to encode a string value in a HTML encoding form as defined in by the HTML specification.

As an example, it is useful to encode a URL:

GET _render/template
{
    "source" : {
        "query" : {
            "term": {
                "http_access_log": "{{#url}}{{host}}/{{page}}{{/url}}"
            }
        }
    },
    "params": {
        "host": "https://www.elastic.co/",
        "page": "learn"
    }
}

The previous query will be rendered as:

{
    "template_output" : {
        "query" : {
            "term" : {
                "http_access_log" : "https%3A%2F%2Fwww.elastic.co%2F%2Flearn"
            }
        }
    }
}

Pre-registered template

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You can register search templates by using the stored scripts api.

POST _scripts/<templatename>
{
    "script": {
        "lang": "mustache",
        "source": {
            "query": {
                "match": {
                    "title": "{{query_string}}"
                }
            }
        }
    }
}

This template can be retrieved by

GET _scripts/<templatename>

which is rendered as:

{
    "script" : {
        "lang" : "mustache",
        "source" : "{\"query\":{\"match\":{\"title\":\"{{query_string}}\"}}}",
        "options": {
          "content_type" : "application/json; charset=UTF-8"
        }
    },
    "_id": "<templatename>",
    "found": true
}

This template can be deleted by

DELETE _scripts/<templatename>

To use a stored template at search time use:

GET _search/template
{
    "id": "<templateName>", 
    "params": {
        "query_string": "search for these words"
    }
}

Name of the stored template script.

Validating templates

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A template can be rendered in a response with given parameters using

GET _render/template
{
  "source": "{ \"query\": { \"terms\": {{#toJson}}statuses{{/toJson}} }}",
  "params": {
    "statuses" : {
        "status": [ "pending", "published" ]
    }
  }
}

This call will return the rendered template:

{
  "template_output": {
    "query": {
      "terms": {
        "status": [ 
          "pending",
          "published"
        ]
      }
    }
  }
}

status array has been populated with values from the params object.

Pre-registered templates can also be rendered using

GET _render/template/<template_name>
{
  "params": {
    "..."
  }
}

Explain

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You can use explain parameter when running a template:

GET _search/template
{
  "id": "my_template",
  "params": {
    "status": [ "pending", "published" ]
  },
  "explain": true
}

Profiling

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You can use profile parameter when running a template:

GET _search/template
{
  "id": "my_template",
  "params": {
    "status": [ "pending", "published" ]
  },
  "profile": true
}

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