Briefly, this error occurs when Elasticsearch attempts to perform a join operation but cannot find a join key in the sample data. The join key is essential for linking documents in a parent-child or nested relationship. To resolve this issue, ensure that your data includes a join field. This field should be properly mapped and contain the necessary parent and child documents. Also, check your query to ensure it correctly references the join field. If the join field is missing or incorrectly referenced, Elasticsearch cannot perform the join operation, leading to this error.
This guide will help you check for common problems that cause the log ” A sample must have at least one join key; found none ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: parser, plugin, join.
Log Context
Log “A sample must have at least one join key; found none” class name is LogicalPlanBuilder.java. We extracted the following from Elasticsearch source code for those seeking an in-depth context :
if (queries.size() < 2) {
throw new ParsingException(source; "A sample requires a minimum of 2 queries; found [{}]"; queries.size());
} if (hasMissingJoinKeys) {
throw new ParsingException(missingJoinKeysSource; "A sample must have at least one join key; found none");
} return new Sample(source; queries);
}
