Debug date math errors in Painless

When you work with date fields in runtime mappings, accessing methods directly on the document field object can cause errors if the proper value accessor is not used.

Follow these guidelines to avoid date operation errors in your Painless scripts:

Always use .value when accessing single values from document fields in Painless.
Check for empty fields when the field might not exist in all documents.
Date arithmetic should be performed on the actual date value, not the field container object.

For details, refer to the following sample error and solution.

Sample error

{
  "error": {
    "root_cause": [
      {
        "type": "script_exception",
        "reason": "runtime error",
        "script_stack": [
          """emit(orderDate.toInstant().toEpochMilli() + 14400000);
        """,
          "              ^---- HERE"
        ],
        "script": " ...",
        "lang": "painless",
        "position": {
          "offset": 75,
          "start": 61,
          "end": 124
        }
      }
    ],
    "type": "search_phase_execution_exception",
    "reason": "all shards failed",
    "phase": "query",
    "grouped": true,
    "failed_shards": [
      {
        "shard": 0,
        "index": "kibana_sample_data_ecommerce",
        "node": "CxMTEjvKSEC0k0aTr4OM3A",
        "reason": {
          "type": "script_exception",
          "reason": "runtime error",
          "script_stack": [
            """emit(orderDate.toInstant().toEpochMilli() + 14400000);
        """,
            "              ^---- HERE"
          ],
          "script": " ...",
          "lang": "painless",
          "position": {
            "offset": 75,
            "start": 61,
            "end": 124
          },
          "caused_by": {
            "type": "illegal_argument_exception",
            "reason": "dynamic method [org.elasticsearch.index.fielddata.ScriptDocValues.Dates, toInstant/0] not found"
          }
        }
      }
    ]
  },
  "status": 400
}

Problematic code

"script": {
  "lang": "painless",
  "source": """
    def orderDate = doc['order_date'];
    emit(orderDate.toInstant().toEpochMilli() + 14400000);
  """
}

Root cause

The script attempts to call toInstant() directly on a ScriptDocValues.Dates object. Date fields in Painless require accessing the .value property to get the actual date value before calling date methods.

Solution

Access the date value using .value before calling date methods:

"script": {
  "lang": "painless",
  "source": """
    def orderDate = doc['order_date'].value;
    emit(orderDate.toInstant().toEpochMilli() + 14400000);
  """
}

Appended .value to the method.