Partial update error. Reason: "Left-hand side cannot be assigned a value."

Elastic Stack Kibana
1

Hi

I'm trying to update an index-pattern in .kibana to contain another scripted field. In testing partial update of the document field I get an error. The partial update was the following:

curl -XPOST 'localhost:9200/.kibana/doc/index-pattern:5cd01980-e173-11e7-b90c-9930744e76ad/_update?pretty' -H 'Content-Type: application/json' -d'
{
"script" : "ctx._source.index\u002Dpattern.title = \u0027pddd\u0027"
}
'

but it returned the following:

{
"error" : {
"root_cause" : [
{
"type" : "remote_transport_exception",
"reason" : "[_Mtk082][127.0.0.1:9300][indices:data/write/update[s]]"
}
],
"type" : "illegal_argument_exception",
"reason" : "failed to execute script",
"caused_by" : {
"type" : "script_exception",
"reason" : "compile error",
"script_stack" : [ ],
"script" : "ctx._source.index-pattern.title = 'pddd'",
"lang" : "painless",
"caused_by" : {
"type" : "illegal_argument_exception",
"reason" : "Left-hand side cannot be assigned a value."
}
}
},
"status" : 400
}

Any ideas why?

2

Have you tried updating this index pattern in the UI? https://www.elastic.co/guide/en/kibana/current/scripted-fields.html

3

I'm trying to automate the creation of scripted fields, so using the UI is not an option

4

So that error is thrown by the Painless compiler trying to compile that script. I think it is trying to run your script rather than taking that as an update to the index-pattern. The saved object looks like this:

{
  "_index": ".kibana",
  "_type": "doc",
  "_id": "index-pattern:949c2fc0-0216-11e8-ba5f-d90822c14a01",
  "_version": 3,
  "found": true,
  "_source": {
    "type": "index-pattern",
    "updated_at": "2018-01-25T21:28:54.558Z",
    "index-pattern": {
      "title": "billy*",
      "fields": """[{"name":"_id","type":"string","count":0,"scripted":false,"searchable":true,"aggregatable":true,"readFromDocValues":false},{"name":"_index","type":"string","count":0,"scripted":false,"searchable":true,"aggregatable":true,"readFromDocValues":false},{"name":"_score","type":"number","count":0,"scripted":false,"searchable":false,"aggregatable":false,"readFromDocValues":false},{"name":"_source","type":"_source","count":0,"scripted":false,"searchable":false,"aggregatable":false,"readFromDocValues":false},{"name":"_type","type":"string","count":0,"scripted":false,"searchable":true,"aggregatable":true,"readFromDocValues":false},{"name":"billy","type":"string","count":0,"scripted":false,"searchable":true,"aggregatable":false,"readFromDocValues":false},{"name":"billy.keyword","type":"string","count":0,"scripted":false,"searchable":true,"aggregatable":true,"readFromDocValues":true},{"name":"script","type":"number","count":0,"scripted":true,"script":"doc['billy']","lang":"painless","searchable":true,"aggregatable":true,"readFromDocValues":false}]"""
    }
  }
}

I think you would need to update the "fields" field in the _source field and append your new scripted field to that array.

Maybe you could explain in more detail what you are trying to do.

5

I'm trying to do exactly as you said. Perform a partial update to update ._source.index-pattern.fields with the appended scripted field. But I believe the problem is index-pattern contains a hash-minus, so "script" : "ctx._source.index-pattern.fields" throws an error. I tried using Unicode \u002D as a replacement, but it still doesn't work.

6

If that is the case, you could try this style of accessing the field:
obj['attr']
This might sort out your issue.

7

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