elastic/elasticsearch · error · ParsingException

Unknown key for a {token} in [{reducerName}]: [{currentField

Error message

Unknown key for a {token} in [{reducerName}]: [{currentFieldName}].

What it means

Error "Unknown key for a {token} in [{reducerName}]: [{currentFieldName}]." thrown in elastic/elasticsearch.

Source

Thrown at modules/aggregations/src/main/java/org/elasticsearch/aggregations/pipeline/BucketSelectorPipelineAggregationBuilder.java:114

        XContentParser.Token token;
        Script script = null;
        String currentFieldName = null;
        Map<String, String> bucketsPathsMap = null;
        GapPolicy gapPolicy = null;

        while ((token = parser.nextToken()) != XContentParser.Token.END_OBJECT) {
            if (token == XContentParser.Token.FIELD_NAME) {
                currentFieldName = parser.currentName();
            } else if (token == XContentParser.Token.VALUE_STRING) {
                if (BUCKETS_PATH.match(currentFieldName, parser.getDeprecationHandler())) {
                    bucketsPathsMap = new HashMap<>();
                    bucketsPathsMap.put("_value", parser.text());
                } else if (GAP_POLICY.match(currentFieldName, parser.getDeprecationHandler())) {
                    gapPolicy = GapPolicy.parse(parser.text(), parser.getTokenLocation());
                } else if (Script.SCRIPT_PARSE_FIELD.match(currentFieldName, parser.getDeprecationHandler())) {
                    script = Script.parse(parser);
                } else {
                    throw new ParsingException(
                        parser.getTokenLocation(),
                        "Unknown key for a " + token + " in [" + reducerName + "]: [" + currentFieldName + "]."
                    );
                }
            } else if (token == XContentParser.Token.START_ARRAY) {
                if (BUCKETS_PATH.match(currentFieldName, parser.getDeprecationHandler())) {
                    List<String> paths = new ArrayList<>();
                    while ((token = parser.nextToken()) != XContentParser.Token.END_ARRAY) {
                        String path = parser.text();
                        paths.add(path);
                    }
                    bucketsPathsMap = new HashMap<>();
                    for (int i = 0; i < paths.size(); i++) {
                        bucketsPathsMap.put("_value" + i, paths.get(i));
                    }
                } else {
                    throw new ParsingException(
                        parser.getTokenLocation(),

View on GitHub (pinned to db6a809a66)

When it happens

Trigger: Thrown at modules/aggregations/src/main/java/org/elasticsearch/aggregations/pipeline/BucketSelectorPipelineAggregationBuilder.java:114 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/cdaac024da95827d. Report an issue: GitHub.