How to get all documents from a filter in Elasticsearch?

Question

If I deliver the empty params (see below) I would like to get all documents from Elasticsearch. How can I achieve this?

One solution is that I could write all the existing categories into an array. But I have more than 100 categories and this will not be a good solution.

Can someone please help me? Is it possible to ignore the terms if the array is empty?

POST _scripts/test{"script": {
"lang": "mustache",
"source": {
  "query": {
    "bool": {
      "must": {
        "match_all": {}
      },
      "filter": {
        "terms": {
          "category": [
            "{{#category}}",
            "{{.}}",
            "{{/category}}"
          ]}}}}}}}

If I execute the below query the results will be empty:

GET poi/_search/template{
"id": "test", 
"params": {
    "category" : [""]
}}

Answer 1

The best way to achieve this would be to proceed like this with a JSON array:

POST _scripts/test
{
  "script": {
    "lang": "mustache",
    "source": """
    {
      "query": {
        "bool": {
          "must": {
            "match_all": {}
          },
          "filter": [
            {{#category}}
            {
              "terms": {
                "category": {{#toJson}}category.values{{/toJson}}
              }
            }
            {{/category}}
          ]
        }
      }
    }
    """
  }
}

Then you can execute this search template like this:

GET poi/_search/template
{
  "id": "test", 
  "params": {
    "category" : {
      "values": ["cat1", "cat2", "cat3"]
    }
  }
}

And if you don't want to specify any categories, like this:

GET poi/_search/template
{
  "id": "test", 
  "params": {
  }
}