Illegal field multiFieldName only fields can be specified inside fields – How to solve this Elasticsearch exception

Opster Team

August-23, Version: 6.8-8.9

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Briefly, this error occurs when you’re trying to specify a non-field inside the “fields” section of an Elasticsearch query. This is not allowed as only actual fields can be specified in this section. To resolve this issue, ensure that you’re only specifying actual fields in the “fields” section. If you’re trying to specify a nested field, make sure to use the correct dot notation. Also, check your query for any typos or incorrect field names. Lastly, ensure that the field you’re specifying actually exists in your Elasticsearch index.

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This guide will help you check for common problems that cause the log ” illegal field [” + multiFieldName + “]; only fields can be specified inside fields ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: index.

Log Context

Log “illegal field [” + multiFieldName + “]; only fields can be specified inside fields” class name is We extracted the following from Elasticsearch source code for those seeking an in-depth context :

 throw new MapperParsingException(
 "Field name [" + multiFieldName + "] which is a multi field of [" + name + "] cannot contain '.'"
 if ((multiFieldEntry.getValue() instanceof Map) == false) {
 throw new MapperParsingException("illegal field [" + multiFieldName + "]; only fields can be specified inside fields");
 Map multiFieldNodes = (Map) multiFieldEntry.getValue();  String type;
 Object typeNode = multiFieldNodes.get("type");


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