Elasticsearch partial update of Object(multi=True)

Question

How to update document with field mapping Object(multi=True), when a document can have both single (dictionary) and multiple values (list of dictionaries).

Example of documents in the same index:

A single value in items:

{
    "title": "Some title",
    "items": {
        "id": 123,
        "key": "foo"
    }
}

Multiple values in items:

{
    "title": "Some title",
    "items": [{
        "id": 456,
        "key": "foo"
    }, {
        "id": 789,
        "key": "bar"
    }]
}

Answer 1

You can try to use the following script.
I intentionally formatted inline attribute to show what's inside.

POST index_name/_update_by_query
{
    "search": {
        "term": {
            "items.key": "foo"
        }
    },
    "script": {
        "inline": "
            if (ctx._source.items instanceof List) {
                for (item in ctx.source.items) {
                    if (item.key == params.old_value) {
                        item.key = params.new_value;
                        break;
                    }
                }
            } else {
                ctx._source.items.key = params.new_value;
            }
        ",
        "params": {"old_value": "foo", "new_value": "bar"},
        "lang": "painless'
    }
}

And to make it work, replace inline attribute with a single line value.

"inline": "if (ctx._source.items instanceof List) {for (item in ctx.source.items) {if (item.key == params.old_value) {item.key = params.new_value;break;}}} else {ctx._source.items.key = params.new_value;}"