elastic/elasticsearch · error · IllegalArgumentException

Token filter [{name}] cannot be used to parse synonyms

Error message

Token filter [{name}] cannot be used to parse synonyms

What it means

Error "Token filter [{name}] cannot be used to parse synonyms" thrown in elastic/elasticsearch.

Source

Thrown at modules/analysis-common/src/main/java/org/elasticsearch/analysis/common/CJKBigramFilterFactory.java:87

    @Override
    public TokenStream create(TokenStream tokenStream) {
        CJKBigramFilter filter = new CJKBigramFilter(tokenStream, flags, outputUnigrams);
        if (outputUnigrams) {
            /**
             * We disable the graph analysis on this token stream
             * because it produces bigrams AND unigrams.
             * Graph analysis on such token stream is useless and dangerous as it may create too many paths
             * since shingles of different size are not aligned in terms of positions.
             */
            filter.addAttribute(DisableGraphAttribute.class);
        }
        return filter;
    }

    @Override
    public TokenFilterFactory getSynonymFilter() {
        if (outputUnigrams) {
            throw new IllegalArgumentException("Token filter [" + name() + "] cannot be used to parse synonyms");
        }
        return this;
    }
}

View on GitHub (pinned to db6a809a66)

When it happens

Trigger: Thrown at modules/analysis-common/src/main/java/org/elasticsearch/analysis/common/CJKBigramFilterFactory.java:87 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of elastic/elasticsearch@db6a809a66 (2026-08-12). Data as JSON: /api/errors/6e187468dbb8bc34. Report an issue: GitHub.