Elasticsearch: truncate a field using a script processor

truncate_field.json

PUT _ingest/pipeline/truncate-field
{
  "description": "Use the Script processor to truncate a field to 10 characters",
  "processors": [
    {
      "script": {
        "inline": "ctx.foo = ctx.foo.substring(0, (int) Math.min(10, ctx.foo.length()))"
      }
    }
  ]
}

# Simulate request
POST _ingest/pipeline/truncate-field/_simulate
{
  "docs" : [
    {
      "_source": {
        "foo": "0123456789 this will be truncated"
      }
    },
    {
      "_source": {
        "foo": "98765"
      }
    },
    {
      "_source": {
        "foo": "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
      }
    }
  ]
}

# Simulate response
{
  "docs": [
    {
      "doc": {
        "_type": "_type",
        "_id": "_id",
        "_index": "_index",
        "_source": {
          "foo": "0123456789"
        },
        "_ingest": {
          "timestamp": "2017-02-09T15:31:36.905Z"
        }
      }
    },
    {
      "doc": {
        "_type": "_type",
        "_id": "_id",
        "_index": "_index",
        "_source": {
          "foo": "98765"
        },
        "_ingest": {
          "timestamp": "2017-02-09T15:31:36.905Z"
        }
      }
    },
    {
      "doc": {
        "_type": "_type",
        "_id": "_id",
        "_index": "_index",
        "_source": {
          "foo": "ABCDEFGHIJ"
        },
        "_ingest": {
          "timestamp": "2017-02-09T15:31:36.905Z"
        }
      }
    }
  ]
}