Unknown function – How to solve this Elasticsearch exception

Opster Team

August-23, Version: 6.8-8.9

Briefly, this error occurs when Elasticsearch encounters a function in a query that it doesn’t recognize. This could be due to a typo, incorrect syntax, or the function may not be supported in the version of Elasticsearch you’re using. To resolve this issue, you should first check the function name and syntax for any errors. If the function is correct, ensure that it is supported in your Elasticsearch version. If it’s not, you may need to update Elasticsearch or find an alternative function.

This guide will help you check for common problems that cause the log ” Unknown function [{}] ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: parser, plugin.

Log Context

Log “Unknown function [{}]” class name is ExpressionBuilder.java. We extracted the following from Elasticsearch source code for those seeking an in-depth context :

 default -> throw new ParsingException(source; "Unknown function [{}]"; functionName);
 }  @Override
 public Function visitFunctionExpression(FunctionExpressionContext ctx) {