Unknown parameter boost on mapper name – How to solve this Elasticsearch exception

Opster Team

August-23, Version: 8-8.9

Briefly, this error occurs when you try to use the [boost] parameter on a field mapping, which is no longer supported in newer versions of Elasticsearch. To resolve this issue, you can remove the [boost] parameter from your mapping and instead apply boosting at query time. Alternatively, you can downgrade to an older version of Elasticsearch that supports the [boost] parameter, but this is not recommended due to potential security and performance issues.

This guide will help you check for common problems that cause the log ” Unknown parameter [boost] on mapper [” + name + “] ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: index.

Log Context

Log “Unknown parameter [boost] on mapper [” + name + “]” class name is FieldMapper.java. We extracted the following from Elasticsearch source code for those seeking an in-depth context :

 case "boost" -> {
 if (parserContext.indexVersionCreated().onOrAfter(IndexVersion.V_8_0_0)) {
 throw new MapperParsingException("Unknown parameter [boost] on mapper [" + name + "]");
 "Parameter [boost] on field [{}] is deprecated and has no effect";