Elasticsearch Version

9.0 and before

Installed Plugins

No response

Java Version

bundled

OS Version

Problem Description

default_metric mapping parameter is lost during downsampling.

Steps to Reproduce

Downsample an index with the following mapping:

"m": {
  "type": "aggregate_metric_double",
  "metrics": ["min", "max", "sum", "value_count"],
  "default_metric": "min",
  "time_series_metric": "gauge"
}

Downsampled index has the following mapping:

"m": {
    "type": "aggregate_metric_double",
    "metrics": [
        "min",
        "max",
        "sum",
        "value_count"
    ],
    "default_metric": "max",
    "time_series_metric": "gauge"
}

Note the change of default_metric from min to max.

Logs (if relevant)

No response