Return the nested object corresponding to the copy_to field in elasticsearch

Question

Here is the structure of my index. An Event has many nested objects : documents, sites, and persons.

Some fields on some nested objects are copy_to to the root.

Events
|--- persons—names
|--- other fields
|
|———— Documents
          --------- other fields
|
|———— Sites
          ---------- other fields
|
|———— Persons
           -----------name (copied to the root)
           ------------- id

Now let's say I am doing a query string search.

If a document is returned BECAUSE it matched with persons_names I want to return only the inner_hit of the associated object, which is "persons" in that case. Note that there may be multiple persons in the document and I need to return exactly the one that matched, so this might be an issue because copy_to is an array that doesn't point to its associated nested object.

Of course I want the same thing to happen if the result matched because of a field copied from "sites" or "documents".

This way, I will be able to create a multi object search --> What I mean by that is that I will return either an event, document, site or person, depending what matched with the query.

How can I do that ? Feel free to redirect me to another approach to solve my multi-object search problem.

misterone misterone · Accepted Answer · 2020-03-03T00:44:59

Using the Explain API could be a good approach, as discussed here : https://discuss.elastic.co/t/best-way-to-return-which-field-matched/4140/3

So the solution would be to :

Make the query_string query
for each results :
- Use the explain API on them (using their ids)
- Analyze the explain API's results and tries to find if the result matched because of a person, site or document field.
- return only the corresponding nested object.

This seems really complex though.

An other option would be to add a new document in my index for each nested object. This would look like this :

Events
|
|--- other fields
|
|———— Documents
|         --------- other fields
|
|———— Sites
|          ---------- other fields
|
|———— Persons
           -----------name (NOT copied to the root)
           ------------- id

### And on the same index, you have other documents for each nested objects

Persons
-----------name (NOT copied to the root)
------------- id
Sites
---------- other fields

Documents
--------- other fields

Then the query_string is straight forward.

Last alternative is to use an index for each type of those objects and query all those indices at the same time.

Return the nested object corresponding to the copy_to field in elasticsearch

1 Answers