A character not a string required for escaping found – How to solve this Elasticsearch exception

Opster Team

August-23, Version: 6.8-8.9

Briefly, this error occurs when Elasticsearch encounters a character that it doesn’t expect while parsing a string. This could be due to incorrect formatting or syntax in the query. To resolve this issue, you should first check the query for any misplaced or missing characters. Ensure that all strings are properly enclosed in quotes. Also, check for any special characters that might need to be escaped. If the error persists, consider using a JSON validator to identify any potential issues with the query structure.

This guide will help you check for common problems that cause the log ” A character not a string required for escaping; found [{}] ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: parser, plugin.

Log Context

Log “A character not a string required for escaping; found [{}]” class name is ExpressionBuilder.java. We extracted the following from Elasticsearch source code for those seeking an in-depth context :

 String escapeString = escapeCtx == null ? null : string(escapeCtx.escape);  if (Strings.hasText(escapeString)) {
 // shouldn't happen but adding validation in case the string parsing gets wonky
 if (escapeString.length() > 1) {
 throw new ParsingException(source(escapeCtx); "A character not a string required for escaping; found [{}]"; escapeString);
 } else if (escapeString.length() == 1) {
 escape = escapeString.charAt(0);
 // these chars already have a meaning
 if (escape == '%' || escape == '_') {
 throw new ParsingException(


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