Allow for executing queries based on pre-defined templates

[MaineC]

It would be nice to be able to store pre-defined query templates that can be referenced and filled with parameter values at query time. This can be in particular useful to be able to quickly replay queries with slightly different templates but identical parameter values e.g. in order to compare slightly different ways to formulate Elasticsearch queries wrt. runtime performance and actual results returned.

For developing and testing the template, both, template_string and template_vars can be submitted as part of the search request:

GET _search
{
    "query": {
        "template": {
            "template_string": "{\"match_{{template}}\": {}}\"",
            "template_vars" : {
                "template" : "all"
            }
        }
    }
}

You register a template by storing it in the conf/scripts directory of
elasticsearch. In order to execute the stored template reference it in the query parameters:

GET _search
{
    "query": {
        "template": {
            "template_string": "storedTemplate",
            "template_vars" : {
                "template" : "all"
            }
        }
    }
}

Template language

Templating is based on Mustache. Substitution of tokens works as follows:

            "template_string": "{\"match_{{template}}\": {}}\"",
            "template_vars" : {
                "template" : "all"

[kimchy]

can we also support

{
    "query": {
        "template": {
            "query": {
                "match_{{template}}" : {}
            }
            "params" : {
                "template" : "all"
            }
        }
    }
}

this is much more readable? we can also make it super fast by using a new XContentBuilder and calling copyCurrentStructure, and running the template on it.

UPDATE:

Also, based on above, I would go with

{
    "query": {
        "template": {
            "query": "{\"match_{{template}}\": {}}\"",
            "params" : {
                "template" : "all"
            }
        }
    }
}

when in "string/bytes" mode, we can detect that, and its more readable.

[uboness]

or

{
    "query": {
        "template": {
            "template": {
                "match_{{template}}" : {}
            }
            "vars" : {
                "template" : "all"
            }
        }
    }
}

[uboness]

and

{
    "query": {
        "template": {
            "name": "storedTemplate",
            "vars" : {
                "template" : "all"
            }
        }
    }
}

[MaineC]

Makes sense - makes it also easier to simply copy/paste existing queries into templates.

[gedl]

Is it possible to create templates at runtime as opposed to pre-package them in the config folder ?

[clintongormley]

@gedl yes - see template query and search template