Should be a hash but was of type – How to solve this Elasticsearch exception

Opster Team

August-23, Version: 6.8-8.9

Briefly, this error occurs when Elasticsearch expects a hash (a data structure that contains key-value pairs) but receives a different data type. This could be due to incorrect data input or a mismatch in the data structure. To resolve this issue, you should first verify the data type you’re sending to Elasticsearch. Ensure it matches the expected hash structure. If the error persists, check your Elasticsearch mapping to ensure it aligns with the data you’re sending. Lastly, consider using a tool to validate your JSON before sending it to Elasticsearch.

This guide will help you check for common problems that cause the log ” should be a hash but was of type: ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: .

Log Context

Log “should be a hash but was of type:” class name is We extracted the following from Elasticsearch source code for those seeking an in-depth context :

 public static Map nodeMapValue(Object node; String desc) {
 if (node instanceof Map) {
 return (Map) node;
 } else {
 throw new ElasticsearchParseException(desc + " should be a hash but was of type: " + node.getClass());
 }  /**
 * Returns an array of string value from a node value.


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