Analyzer returning alternating results on each request

OpenSearch
1

Versions (relevant - OpenSearch/Dashboard/Server OS/Browser):
2.9.0 using Docker, MacOS Ventura, Firefox

Describe the issue:
I followed this guide: How to Use the Synonyms Feature Correctly in Elasticsearch | by Lynn Kwong | Towards Data Science to configure an analyzer filtering tokens against a synonyms.txt.
However, when I try the analyzer, if I keep on making the same request, it indefinitely alternates between returning the term I give as a token and returning the term plus its synonyms:

First result:

{
  "tokens": [
    {
      "token": "PS",
      "start_offset": 0,
      "end_offset": 6,
      "type": "<ALPHANUM>",
      "position": 0
    }
  ]
}

Second result:

{
  "tokens": [
    {
      "token": "PlayStation",
      "start_offset": 0,
      "end_offset": 6,
      "type": "SYNONYM",
      "position": 0
    },
    {
      "token": "PS",
      "start_offset": 0,
      "end_offset": 6,
      "type": "<ALPHANUM>",
      "position": 0
    }
  ]
}

As a result (I think) search queries behave non-deterministically (I guess it’s not REALLY non-deterministic since it has a pattern, but the point is, it gives me different results on the same request).

I’m a completely newbie to Elastic/OpenSearch but I can’t imagine this is the expected behavior?

Thank you.

Configuration:

PUT /inventory_synonym_graph_file
{
  "settings": {
    "index": {
      "analysis": {
        "analyzer": {
          "index_analyzer": {
            "tokenizer": "standard",
            "filter": [
              "lowercase"
            ]
          },
          "search_analyzer": {
            "tokenizer": "standard",
            "filter": [
              "lowercase",
              "synonym_filter"
            ]
          }
        },
        "filter": {
          "synonym_filter": {
            "type": "synonym_graph",
            "synonyms_path": "synonyms.txt",
            "updateable": true
          }
        }
      }
    }
  },
  "mappings": {
    "properties": {
      "name": {
        "type": "text",
        "analyzer": "index_analyzer",
        "search_analyzer": "search_analyzer"
      }
    }
  }
}

Relevant Logs or Screenshots:

2

Assuming you make _analyze calls against the same index of the same cluster, this is definitely not expected behavior.

If it’s not an API-calling quirk (maybe you’re looking at a different index sometimes?), I have three ideas:

  1. Maybe the synonyms.txt file isn’t on all the nodes? And sometimes you hit a node that doesn’t have it?
  2. Maybe updateable=true somehow breaks it? I’m not sure that OpenSearch supports it, I thought it’s a non-OSS Elasticsearch feature, but maybe OpenSearch has it too, I’d have to double-check
  3. You’d typically want to expand synonyms at query time - because then you can update the synonyms list without reindexing (which is where updateable=true should come into play) and it will work better with multi-word synonyms (e.g. if you want Play Station to be the equivalent of PS)