Cannot use reserved field name mapper name – How to solve this Elasticsearch exception

Opster Team

August-23, Version: 7.11-8.9

Briefly, this error occurs when you try to use a field name in Elasticsearch that is reserved for internal use. Elasticsearch has certain field names that are reserved and cannot be used for your own fields. If you try to use one of these reserved names, you will get this error. To resolve this issue, you should rename your field to something that is not reserved. You can also check the Elasticsearch documentation for a list of reserved field names to avoid this issue in the future.

This guide will help you check for common problems that cause the log ” Cannot use reserved field name [” + + “] ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: index.

Log Context

Log “Cannot use reserved field name [” + + “]” class name is We extracted the following from Elasticsearch source code for those seeking an in-depth context :

 TextFieldType tft = buildFieldType(fieldType; multiFields; context; indexCreatedVersion);
 SubFieldInfo phraseFieldInfo = buildPhraseInfo(fieldType; tft);
 SubFieldInfo prefixFieldInfo = buildPrefixInfo(context; fieldType; tft);
 for (Mapper mapper : multiFields) {
 if ( || {
 throw new MapperParsingException("Cannot use reserved field name [" + + "]");
 return new TextFieldMapper(


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