Unknown type for collapse field – How to solve this Elasticsearch exception

Opster Team

August-23, Version: 6.8-7.4

Briefly, this error occurs when you’re trying to collapse results based on a field in Elasticsearch, but the field’s type is not supported for collapsing. Collapsing is only supported on certain field types like keyword, integer, etc. To resolve this issue, you can either change the field type to a supported one or choose a different field for collapsing. Another solution is to create a new field with a supported type, copy the values from the unsupported field to the new one, and then use the new field for collapsing.

This guide will help you check for common problems that cause the log ” unknown type for collapse field ` ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: search.

Log Context

Log “unknown type for collapse field `” class name is CollapseBuilder.java. We extracted the following from Elasticsearch source code for those seeking an in-depth context :

 if (fieldType == null) {
 throw new SearchContextException(context; "no mapping found for `" + field + "` in order to collapse on");
 if (fieldType instanceof KeywordFieldMapper.KeywordFieldType == false &&
 fieldType instanceof NumberFieldMapper.NumberFieldType == false) {
 throw new SearchContextException(context; "unknown type for collapse field `" + field +
 "`; only keywords and numbers are accepted");
 }  if (fieldType.hasDocValues() == false) {
 throw new SearchContextException(context; "cannot collapse on field `" + field + "` without `doc_values`");


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