[BUG] Unnecessary error message when trying to modify an index, even when it succeeds

[gyaneshgupta96]

What is the bug?

Index modified successfully using terraform, but still error shows up.

Error: There are documents in the index (or the index could not be , set force_destroy to true to allow destroying.`

How can one reproduce the bug?

If I create an index lets say something like this:

resource "opensearch_index" "sample_index" {
    name               = "sample_index"
    number_of_shards   = "3"
    number_of_replicas = "3"
    refresh_interval   = "-1"
   mappings = jsonencode(
        {
       "properties:{
       "department_id" : {
          "type" : "keyword"
        },
        "document" : {
          "type" : "keyword"
        },
        "text" : {
          "type" : "keyword"
        },
     }
}

If I modify such that

resource "opensearch_index" "sample_index" {
    name               = "sample_index"
    number_of_shards   = "3"
    number_of_replicas = "3"
    refresh_interval   = "-1"
   mappings = jsonencode(
        {
       "properties:{
       "department_id" : {
          "type" : "keyword"
        },
       "department_name" : {
          "type" : "keyword"
        },
        "document" : {
          "type" : "keyword"
        },
        "text" : {
          "type" : "keyword"
        },
     }
}

I see this error coming up.

However, if you do get index?settings, the field department_name gets added. Worst, this error persists.

What is the expected behavior?

The error should not persist. The only way to get rid of the error is by deleting the index, which is unacceptable in production environment. Either it should not make the change (throwing an error) and then reverting the terraform config should fix things. Or make the change and be done with it.

What is your host/environment?

macos, latest version of the provider.

[prudhvigodithi]

[Triage]
Adding @rblcoder to please provide some details.
Thanks

[rblcoder]

Static settings such as mapping to be only be defined at the index creation time.
https://aws.amazon.com/blogs/big-data/patterns-for-updating-amazon-opensearch-service-index-settings-and-mappings/

[gyaneshgupta96]

A followup question? What is the best way then to allow for dynamic mappings and ensure the index state doesn't create an issue? I want to be able to change mappings or atleast have a dynamic mapping. It should not delete the index based on the state.

[rblcoder]

From the documentation -
https://registry.terraform.io/providers/opensearch-project/opensearch/latest/docs/resources/index

mappings (String) A JSON string defining how documents in the index, and the fields they contain, are stored and indexed. To avoid the complexities of field mapping updates, updates of this field are not allowed via this provider.