Error reindexing "Field [_source] is defined both as an object and a field."

Elastic Stack Elasticsearch
1

I am trying to copy existing index to new index using reindex API

/_reindex?wait_for_completion=false
{
    "source": {
    "index": "articles"
    },
    "dest": {
    "index": "articles20200321"
    },
    "conflicts": "proceed"
}

But it fails after some time with following error

"failures": [
    {
        "index": "articles20200321",
        "type": "_doc",
        "id": "_analyze",
        "cause": {
            "type": "illegal_argument_exception",
            "reason": "Field [_source] is defined both as an object and a field."
        },
        "status": 400
    }
]

There are around 783907 documents and only 126999 get created to new index. Can someone please point to the root cause, or how to identify it?

2

Apparently you have a document which _id is _analyze. It looks weird.

3

Thanks, that was helpful. After deleting the document with id _analyze I was able to successfully reindex.

Seems this document was created by mistake while executing incorrect analyze request.