Cannot verb to a field alias mapper name – How to solve this Elasticsearch exception

Opster Team

August-23, Version: 8.1-8.1

Briefly, this error occurs when an operation is attempted on a field alias in Elasticsearch. Field aliases are like pointers to actual fields and cannot be directly modified. To resolve this issue, you should perform the operation on the original field that the alias points to. Alternatively, you can create a new field alias if you need to change the field it points to. Lastly, ensure your application code is correctly identifying and handling field aliases.

This guide will help you check for common problems that cause the log ” Cannot ” + verb + ” to a field alias [” + + “]. ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: alias, index.

Log Context

Log “Cannot ” + verb + ” to a field alias [” + + “].” class name is We extracted the following from Elasticsearch source code for those seeking an in-depth context :

 parseCopyFields(context; copyToFields);
 } else if (mapper instanceof FieldAliasMapper) {
 String verb = context.isWithinCopyTo() ? "copy" : "write";
 throw new MapperParsingException("Cannot " + verb + " to a field alias [" + + "].");
 } else {
 throw new IllegalStateException(
 "The provided mapper [" + + "] has an unrecognized type [" + mapper.getClass().getSimpleName() + "]."


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