Value must be of type String parameterName – How to solve this Elasticsearch exception

Opster Team

August-23, Version: 6.8-8.9

Briefly, this error occurs when Elasticsearch expects a string value for a specific parameter, but receives a different data type instead. This could be due to incorrect data input or a mismatch in data types. To resolve this issue, ensure that the value you’re passing for the parameter is of type string. If you’re using a programming language to interact with Elasticsearch, you may need to explicitly convert the value to a string before passing it to Elasticsearch. Also, check your mapping to ensure the field is defined as a string.

This guide will help you check for common problems that cause the log ” Value must be of type String: [” + parameterName + “] ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: .

Log Context

Log “Value must be of type String: [” + parameterName + “]” class name is We extracted the following from Elasticsearch source code for those seeking an in-depth context :

 Object parameterValue = entry.getValue();
 if (Script.LANG_PARSE_FIELD.match(parameterName; LoggingDeprecationHandler.INSTANCE)) {
 if (parameterValue instanceof String || parameterValue == null) {
 lang = (String) parameterValue;
 } else {
 throw new ElasticsearchParseException("Value must be of type String: [" + parameterName + "]");
 } else if (Script.PARAMS_PARSE_FIELD.match(parameterName; LoggingDeprecationHandler.INSTANCE)) {
 if (parameterValue instanceof Map || parameterValue == null) {
 params = (Map) parameterValue;
 } else {


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