Field mapper name is defined more than once – How to solve this OpenSearch exception

Opster Team

Aug-23, Version: 1-2.9

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Briefly, this error occurs when a field in an OpenSearch index is defined multiple times with different types. This is not allowed as it can lead to inconsistencies in data handling. To resolve this issue, you can either rename one of the fields, delete and recreate the index with correct mappings, or reindex the data into a new index with the correct mappings. It’s important to ensure that each field has a unique name and type within an index to avoid such conflicts.

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This guide will help you check for common problems that cause the log ” Field [” + + “] is defined more than once ” to appear. To understand the issues related to this log, read the explanation below about the following OpenSearch concepts: index.

Log Context

Log “Field [” + + “] is defined more than once” class name is We extracted the following from OpenSearch source code for those seeking an in-depth context :

 for (FieldMapper mapper : mappers) {
 if (objects.containsKey( {
 throw new MapperParsingException("Field [" + + "] is defined both as an object and a field");
 if (fieldMappers.put(; mapper) != null) {
 throw new MapperParsingException("Field [" + + "] is defined more than once");
 MappedFieldType fieldType = mapper.fieldType();
 put(indexAnalyzers;; fieldType.indexAnalyzer(); defaultIndex);
 this.metadataFieldCount = metadataFieldCount;


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