Synonym building fails if filter proceeded by compound word filter

[BastianHofmann]

I'm using the official Docker image: docker.elastic.co/elasticsearch/elasticsearch:6.3.2

Elasticsearch version (bin/elasticsearch --version): 6.3.2

Plugins installed: []

JVM version (java -version): 10.0.2

OS version (uname -a if on a Unix-like system): Linux 596b10634157 4.9.93-linuxkit-aufs #1 SMP Wed Jun 6 16:55:56 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux

Description of the problem including expected versus actual behavior:

When creating an index with a custom analyzer with a dictionary_decompounder filter and synonym filter (in this order), the index creation fails with an invalid argument exception.

Steps to reproduce:

1. create index

PUT http://localhost:9200/test

{
    "analysis": {
        "analyzer": {
            "test": {
                "type": "custom",
                "tokenizer": "standard",
                "filter": [
                    "myCompounds",
                    "mySynonyms"
                ]
            }
        },
        "filter": {
            "myCompounds": {
                "type": "dictionary_decompounder",
                "word_list": [
                    "Kaufmann"
                ]
            },
            "mySynonyms": {
                "type": "synonym",
                "synonyms": [
                    "Verkäufer, Kaufmann im Einzelhandel"
                ]
            }
        }
    }
}

2. See error response

{
    "error": {
        "root_cause": [
            {
                "type": "illegal_argument_exception",
                "reason": "failed to build synonyms"
            }
        ],
        "type": "illegal_argument_exception",
        "reason": "failed to build synonyms",
        "caused_by": {
            "type": "parse_exception",
            "reason": "Invalid synonym rule at line 1",
            "caused_by": {
                "type": "illegal_argument_exception",
                "reason": "term: Kaufmann im Einzelhandel analyzed to a token (Kaufmann) with position increment != 1 (got: 0)"
            }
        }
    },
    "status": 400
}

It works if you switch the order of the filters. I know that the synonym list is analyzed with all the filters, that come before the synonym filter. However why would that cause an error as soon as a compound word is included in the synonyms. Shouldn't we just get a list of "Verkäufer, Kaufmann im Einzelhandel, Kaufmann" for a value of "Verkäufer"?

[jimczi]

Thanks for reporting @BastianHofmann , this issue is already fixed by #34331 so I hope you don't mind if I close it.
Starting in 6.6 we don't apply the decompounding when building synonyms so only the original term is used to match the synonym rule.