How to add deletion phase in policy (POST does not seem to work)

[Mark_S (Baldrick)]

I am trying to add a deletion phase in an existing policy. The policy works fine, creating new indices every day.
However, I cannot add a deletion phase. Since this is not possible from the UI, I tried with a POST :

But this does not seem to work... Why are the PUT and POST rejected - is it not possible to update it, only to create a new one that includes the delete phase?

Here is the policy:

{
  "myindexpolicy" : {
    "version" : 1,
    "modified_date" : "2023-02-17T12:05:04.639Z",
    "policy" : {
      "phases" : {
        "hot" : {
          "min_age" : "0ms",
          "actions" : {
            "set_priority" : {
              "priority" : 100
            },
            "rollover" : {
              "max_primary_shard_size" : "1gb",
              "max_age" : "1d"
            }
          }
        }
      }
    },
    "in_use_by" : {
      "indices" : [
        "myindexalias-000008",
        "myindexalias-000009",
        "myindexalias-000015",
        "myindexalias-000004",
        "myindexalias-000016",
        "myindexalias-000005",
        "myindexalias-000006",
        "myindexalias-000017",
        "myindexalias-000007",
        "myindexalias-000011",
        "myindexalias-000012",
        "myindexalias-000013",
        "myindexalias-000002",
        "myindexalias-000003",
        "myindexalias-000014",
        "myindexalias-000010"
      ],
      "data_streams" : [ ],
      "composable_templates" : [
        "mts_template"
      ]
    }
  }
}

And here is the POST (also tried PUT)

POST /_ilm/policy/myindexpolicy/_update
{
  "policy": {
    "phases": {
      "delete": {
        "min_age": "30d",
        "actions": {
          "delete": {}
        }
      }
    }
  }
}

Here is the error message:

{
  "error" : {
    "root_cause" : [
      {
        "type" : "x_content_parse_exception",
        "reason" : "[2:3] [UpdateRequest] unknown field [policy]"
      }
    ],
    "type" : "x_content_parse_exception",
    "reason" : "[2:3] [UpdateRequest] unknown field [policy]"
  },
  "status" : 400
}

PUT gives

 "error" : "Incorrect HTTP method for uri [/_ilm/policy/myindexpolicy/_update?pretty=true] and method [PUT], allowed: [POST]",
  "status" : 405

[stephenb (Stephen Brown)]

@Mark_S

There is no _update directive for ILM API for create, create and update are the same although it will version the ILM Polocy

You simply PUT a complete new policy, there is no partial update, there is no POST with _update

@Mark_S

Since this is not possible from the UI,

You should be... it is easy to miss but you need to select the little Trashcan symbol on the right hand side

[Mark_S (Baldrick)]

@stephenb : Thank you!