Cannot copy field mapper name to fields – How to solve this Elasticsearch exception

Opster Team

August-23, Version: 7.14-7.15

Briefly, this error occurs when Elasticsearch tries to copy a field to another field using the “copy_to” function, but the destination field doesn’t exist or isn’t properly defined. To resolve this issue, you can either create the destination field if it doesn’t exist, or check the destination field’s definition in the mapping if it does exist. Make sure the field type matches the data type of the source field. Also, ensure that the “copy_to” function is correctly implemented in your mapping.

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

Log Context

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

 List copyToFields = fieldMapper.copyTo().copyToFields();
 if (context.isWithinCopyTo() == false && copyToFields.isEmpty() == false) {
 XContentParser.Token currentToken = context.parser().currentToken();
 if (currentToken.isValue() == false && currentToken != XContentParser.Token.VALUE_NULL) {
 // sanity check; we currently support copy-to only for value-type field; not objects
 throw new MapperParsingException("Cannot copy field [" + + "] to fields " + copyToFields +
 ". Copy-to currently only works for value-type fields; not objects.");
 parseCopyFields(context; copyToFields);
 } else if (mapper instanceof FieldAliasMapper) {