Expected array for field – How to solve this Elasticsearch exception

Opster Team

August-23, Version: 6.8-7.9

Briefly, this error occurs when Elasticsearch expects an array for a specific field, but the provided input is not an array. This usually happens when the data type defined in the mapping is not consistent with the actual data being indexed. To resolve this issue, you can either change the data type in the mapping to match the actual data or modify the data being indexed to match the expected array format. Another solution is to use scripts or ingest pipelines to transform the data into the expected format before indexing.

This guide will help you check for common problems that cause the log ” expected array for [” + field + “] ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: repositories.

Log Context

Log “expected array for [” + field + “]” class name is RepositoryData.java. We extracted the following from Elasticsearch source code for those seeking an in-depth context :

 if (metaGenerations.isEmpty() == false) {
 indexMetaLookup.put(snapshotId; metaGenerations);
 } else {
 throw new ElasticsearchParseException("expected array for [" + field + "]");
 } else if (INDICES.equals(field)) {
 if (parser.nextToken() != XContentParser.Token.START_OBJECT) {
 throw new ElasticsearchParseException("start object expected [indices]");


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