I’m struggling to get a simple post filter to work:

My non filtered query has a few results:

{
  "size": 2,
  "query": {
    "knn": {
      "embedding": {
        "k": 3, "vector": [...]
      }
    }
  }
}

{
  "hits": {
    "total": {
      "value": 634,
      "relation": "eq"
    },
    "max_score": 0.7958787,
    "hits": [
      {
        "_id": "8e4ca013a2b0c0ee1ee5b111c54857e1c9f222a59fe1c450a8e012c72ecbecfd",
        "_score": 0.7958787,
        "_source": {
          "id_embedding": "8e4ca013a2b0c0ee1ee5b111c54857e1c9f222a59fe1c450a8e012c72ecbecfd",
          "embedding": [...],
          "content": """bla bla bla""",
          "metadata": """{"location": "/introduction/index.html" ...}"""
        }
      }
    ]
  }
}

I now add a post_filter like so:

{
  "size": 2,
  "query": {
    "knn": {
      "embedding": {
        "k": 3, "vector": [...]
      }
    }
  },
  "post_filter": {
    "wildcard": { "metadata": "*html*" }
  }
}

and this seem to remove all results, while as seen above some results should match.

{
  "hits": {
    "total": {
      "value": 0,
      "relation": "eq"
    },
    "max_score": null,
    "hits": []
  }
}

I tried several ways to write this filter (match, { "bool": { "must": [ ... ] } } but could never get a result with a post filter.