Cannot expand inner hits for collapse field – How to solve this Elasticsearch exception

Opster Team

August-23, Version: 6.8-7.4

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Briefly, this error occurs when you try to use the `inner_hits` feature with a field that is used for collapsing results in Elasticsearch. The `inner_hits` feature is not compatible with the `collapse` feature. To resolve this issue, you can either remove the `inner_hits` feature from your query or remove the `collapse` feature. Alternatively, you can use a different field for collapsing that doesn’t require the use of `inner_hits`.

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This guide will help you check for common problems that cause the log ” cannot expand `inner_hits` 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 “cannot expand `inner_hits` for collapse field `” class name is We extracted the following from Elasticsearch source code for those seeking an in-depth context :

 if (fieldType.hasDocValues() == false) {
 throw new SearchContextException(context; "cannot collapse on field `" + field + "` without `doc_values`");
 if (fieldType.indexOptions() == IndexOptions.NONE && (innerHits != null && !innerHits.isEmpty())) {
 throw new SearchContextException(context; "cannot expand `inner_hits` for collapse field `"
 + field + "`; " + "only indexed field can retrieve `inner_hits`");
 }  return new CollapseContext(field; fieldType; innerHits);


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