Analyzer must be set for field name but wasn t – 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 missing an analyzer setting. Analyzers are crucial for processing text data during indexing and searching. Without an analyzer, OpenSearch cannot correctly interpret the field data. To resolve this, you can set an analyzer for the field by updating the index mapping. Choose an appropriate built-in analyzer or create a custom one based on your data needs. Alternatively, if the field doesn’t require text analysis, consider changing its data type to non-text such as keyword or integer.

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This guide will help you check for common problems that cause the log ” Analyzer must be set for field [” + name + “] but wasn’t. ” to appear. To understand the issues related to this log, read the explanation below about the following OpenSearch concepts: index.

Log Context

Log “Analyzer must be set for field [” + name + “] but wasn’t.” class name is We extracted the following from OpenSearch source code for those seeking an in-depth context :

 }  @Override
 public TokenCountFieldMapper build(BuilderContext context) {
 if (analyzer.getValue() == null) {
 throw new MapperParsingException("Analyzer must be set for field [" + name + "] but wasn't.");
 MappedFieldType ft = new TokenCountFieldType(


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