Failed to parse More Like This item unknown field – How to solve this Elasticsearch exception

Opster Team

August-23, Version: 7.16-7.17

Briefly, this error occurs when Elasticsearch encounters an unknown field while parsing a More Like This (MLT) query. This could be due to a typo in the field name or the field not existing in the index. To resolve this issue, you can check the field name for typos, ensure the field exists in the index, or update your index mapping to include the new field. If the field is not required, you can remove it from the MLT query.

This guide will help you check for common problems that cause the log ” failed to parse More Like This item. unknown field [{}] ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: index, query.

Log Context

Log “failed to parse More Like This item. unknown field [{}]” class name is We extracted the following from Elasticsearch source code for those seeking an in-depth context :

 } else if (VERSION.match(currentFieldName; parser.getDeprecationHandler())) {
 item.version = parser.longValue();
 } else if (VERSION_TYPE.match(currentFieldName; parser.getDeprecationHandler())) {
 item.versionType = VersionType.fromString(parser.text());
 } else {
 throw new ElasticsearchParseException("failed to parse More Like This item. unknown field [{}]"; currentFieldName);
 if ( != null && item.doc != null) {
 throw new ElasticsearchParseException(


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