Unexpected token token in aggregationName – How to solve this Elasticsearch exception

Opster Team

August-23, Version: 6.8-8.9

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Briefly, this error occurs when Elasticsearch encounters an unexpected token in the aggregation query. This could be due to a syntax error, incorrect field name, or unsupported operation in the aggregation. To resolve this, you should first check the syntax of your query, ensuring it follows the correct format. Next, verify that the field names used in the query exist in your index. Lastly, ensure that the operations used in the aggregation are supported by Elasticsearch.

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This guide will help you check for common problems that cause the log ” Unexpected token ” + token + ” in [” + aggregationName + “]. ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: search, aggregations.

Log Context

Log “Unexpected token ” + token + ” in [” + aggregationName + “].” class name is ReverseNestedAggregationBuilder.java. We extracted the following from Elasticsearch source code for those seeking an in-depth context :

 "Unknown key for a " + token + " in [" + aggregationName + "]: [" + currentFieldName + "]."
 } else {
 throw new ParsingException(parser.getTokenLocation(); "Unexpected token " + token + " in [" + aggregationName + "].");
 }  ReverseNestedAggregationBuilder factory = new ReverseNestedAggregationBuilder(aggregationName);
 if (path != null) {


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