Existence queries unable to match nested object fields

[esatterwhite]

Describe the bug
The field existence query doesn't work on nested field unless the field is terminal

Steps to reproduce (if applicable)

Indexing a document like the following

{
  "foo": {
    "bar": 1
  }
, "whiz": true
}

No Matches

foo:*

Matches

foo:bar:*

Matches

whiz:*

Expected behavior
I would expect a document with a field of foo to match when using the existence query even if the field value is an object. That is the behavior seen by elasticsearch nested fields.

Version Information

{
  "build": {
    "build_date": "2024-10-29T15:18:16Z",
    "build_profile": "release",
    "build_target": "aarch64-unknown-linux-gnu",
    "cargo_pkg_version": "0.8.0",
    "commit_date": "2024-10-29T11:50:14Z",
    "commit_hash": "826f10f0d7ba1a448795890fe296941b84872c57",
    "commit_short_hash": "826f10f",
    "commit_tags": [
      "qw-airmail-20241029"
    ],
    "version": "0.8.0-nightly"
  },
  "runtime": {
    "num_cpus": 16,
    "num_threads_blocking": 14,
    "num_threads_non_blocking": 2
  }
}