[BUG] PPL error `node must be a boolean` when mapping conflicts

[joshuali925]

Query Information

PPL Command/Query:

source = repro*

Expected Result:
response similar to DSL GET repro*/_search with documents returned

Actual Result:

"{\n  \"error\": {\n    \"reason\": \"Error occurred in OpenSearch engine: node must be a boolean, found NUMBER\",\n    \"details\": \"OpenSearchParseException[node must be a boolean, found NUMBER]\\nFor more details, please send request for Json format to see the raw response from OpenSearch engine.\",\n    \"type\": \"OpenSearchParseException\"\n  },\n  \"status\": 400\n}"

Dataset Information

Dataset/Schema Type

• OpenTelemetry (OTEL)
• Simple Schema for Observability (SS4O)
• Open Cybersecurity Schema Framework (OCSF)
• Custom (details below)

Index Mapping

{
  "repro-bb": {
    "mappings": {
      "properties": {
        "flag": {
          "type": "boolean"
        },
        "startTime": {
          "type": "date_nanos"
        }
      }
    }
  },
  "repro-aa": {
    "mappings": {
      "properties": {
        "flag": {
          "type": "text"
        },
        "startTime": {
          "type": "date_nanos"
        }
      }
    }
  }
}

Sample Data

{
  "took": 1,
  "timed_out": false,
  "_shards": {
    "total": 2,
    "successful": 2,
    "skipped": 0,
    "failed": 0
  },
  "hits": {
    "total": {
      "value": 2,
      "relation": "eq"
    },
    "max_score": 1,
    "hits": [
      {
        "_index": "repro-aa",
        "_id": "1",
        "_score": 1,
        "_source": {
          "startTime": "2026-03-24T20:25:00.000Z",
          "flag": 0
        }
      },
      {
        "_index": "repro-bb",
        "_id": "1",
        "_score": 1,
        "_source": {
          "startTime": "2026-03-25T20:25:00.000Z",
          "flag": false
        }
      }
    ]
  }
}

Bug Description

Issue Summary:
opensearch coerces 0 as false for boolean fields, sql should have same behavior

Steps to Reproduce:

1. create the two indices with docs listed above
2. run ppl query as listed above
3. see error

Impact:
can't search indexes with this kind of mapping conflict

Environment Information

OpenSearch Version:
3.6

Additional Details:

It appears #4095 addressed similar problems, but not 0 to false

Screenshots