reindex doesn't accept comma separated values as inputs

[Mekk]

I am trying to merge few small indices into one bigger. It looks like comma-separated list is not supported, contrary to docs. Tested on Elasticsearch 7.5.1.

According to https://www.elastic.co/guide/en/elasticsearch/reference/current/docs-reindex.html page

 index
    (Required, string) The name of the index you are copying from. Also accepts a comma-separated list of indices to reindex from multiple sources. 

So I tried comma separated list:

POST /_reindex?pretty
{"conflicts": "proceed",
  "source": {
    "index": "sfx-pb-1.3.0-2020.03.02,sfx-pb-1.3.0-2020.03.03"
  },
  "dest": {"index": "sfx-pb-1.3.0-2020.03", "op_type": "create"}}

(both indexes mentioned in source exist what GET /sfx-pb-1.3.0-2020.03.02,sfx-pb-1.3.0-2020.03.03 gladly confirmed).

Result:

{
  "error" : {
    "root_cause" : [
      {
        "type" : "index_not_found_exception",
        "reason" : "no such index [sfx-pb-1.3.0-2020.03.02,sfx-pb-1.3.0-2020.03.03]",
        "resource.type" : "index_or_alias",
        "resource.id" : "sfx-pb-1.3.0-2020.03.02,sfx-pb-1.3.0-2020.03.03",
        "index_uuid" : "_na_",
        "index" : "sfx-pb-1.3.0-2020.03.02,sfx-pb-1.3.0-2020.03.03"
      }
    ],
    "type" : "index_not_found_exception",
    "reason" : "no such index [sfx-pb-1.3.0-2020.03.02,sfx-pb-1.3.0-2020.03.03]",
    "resource.type" : "index_or_alias",
    "resource.id" : "sfx-pb-1.3.0-2020.03.02,sfx-pb-1.3.0-2020.03.03",
    "index_uuid" : "_na_",
    "index" : "sfx-pb-1.3.0-2020.03.02,sfx-pb-1.3.0-2020.03.03"
  },
  "status" : 404
}

[Mekk]

(edited as it turned out that globbed value didn't work for me because index was frozen – but for comma-separated values problem persists also after reopening them)

[elasticmachine]

Pinging @elastic/es-distributed (:Distributed/Reindex)

[cbuescher]

Also accepts a comma-separated list of indices to reindex from multiple sources.

I think this could be read as something like:

"source": {
    "index": [ "sfx-pb-1.3.0-2020.03.02", "sfx-pb-1.3.0-2020.03.03" ]
  }

Have you tried that as well?

[Mekk]

No, doc seems to be clearly stating that this param is of type string (and I would never consider array to be „comma separated value” in any case). I will give this format a try next time.

[Mekk]

Looks like sth started using array format. So this is documentation issue - doc should state it clearly and provide an example.

(the same also applies to glob format, which also doesn't have any example and isn't even mentioned in field description)

[elasticmachine]

Pinging @elastic/es-docs (>docs)