No index mapper found for field returning default postings format – How to solve this OpenSearch error

Opster Team

Aug-23, Version: 1-2.9

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Briefly, this error occurs when OpenSearch cannot find an index mapper for a specific field. This means that the field in question is not properly mapped or defined in the index schema. To resolve this issue, you can either create a new index with the correct mapping or update the existing index mapping. Be careful when updating as it can lead to data loss. Also, ensure that your queries are correctly referencing the field names as defined in your mapping.

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This guide will help you check for common problems that cause the log ” no index mapper found for field: [{}] returning default postings format ” to appear. To understand the issues related to this log, read the explanation below about the following OpenSearch concepts: index.

Log Context

Log “no index mapper found for field: [{}] returning default postings format” classname is
We extracted the following from OpenSearch source code for those seeking an in-depth context :

    public PostingsFormat getPostingsFormatForField(String field) {
        final MappedFieldType fieldType = mapperService.fieldType(field);
        if (fieldType == null) {
            logger.warn("no index mapper found for field: [{}] returning default postings format"; field);
        } else if (fieldType instanceof CompletionFieldMapper.CompletionFieldType) {
            return CompletionFieldMapper.CompletionFieldType.postingsFormat();
        return super.getPostingsFormatForField(field);


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