Compare 2 indices and find missing documents

[arks1]

I have 2 indices, index_a and index_b.

The 2 indices have documents with the almost the exact same template. index_b has some extra fields which was introduced as part of a new feature, but it also has all the fields already present in index_a.

We have noticed that that index_b is missing about 2000 documents which are present in index_a. We found this out by using the _count API.

Now the question is, is there a way to find out the actual missing documents? Only the missing Ids should also be enough for a start.

Both the indices have a field called member_id which is unique for each document and is the same as the document id, so retrieving only the missing id fields should also be enough.

I cannot compare the index directly to the source database because this data comes from an external API.

[dadoonet (David Pilato)]

You have to do that "manually".

Search for all documents in the first index, get the ids and then run a multiget API call to check.

[arks1]

Thank you for the response. I got a list of ids from the first index. When I try to use the _mget API, I can see for the ids that do not exist in index_b, the response body contains the following response.

{
    "_index": "tm_member5",
    "_id": "0",
    "found": false
}

I am going to write some logic to be able to extract the ids from the objects where found == false

But just wanted to know if the _mget api itself has any input parameter I can use to do that. I looked at the doc but could not find anything of this sort.

[dadoonet (David Pilato)]

I'd use jq for this. It helps to filter a node and print whatever you need.