Unknown key for a ” + token + ” in – Elasticsearch Error How To Solve Related Issues

Unknown key for a ” + token + ” in – Elasticsearch Error How To Solve Related Issues

Updated: July-20

Elasticsearch Version: 1.7-8.0

Before you begin reading this guide, we recommend you try running the Elasticsearch Error Check-Up  which can resolve issues causing many errors 


This guide will help you check for common problems that cause the log “Unknown key for a ” + token + ” in” to appear. It’s important to understand the issues related to the log, so to get started, read the general overview on common issues and tips related to the Elasticsearch concepts: search.

Advanced users might want to skip right to the common problems section in each concept or try running the Check-Up which analyses ES to discover the cause of many errors and provides suitable actionable recommendations (free tool that requires no installation). 

Log Context

Log”Unknown key for a ” + token + ” in [“classname  is SearchSourceBuilder.java
We extracted the following from Elasticsearch source code for those seeking an in-depth context :

if (SCRIPT_FIELD.match(currentFieldName; parser.getDeprecationHandler())) {
  script = Script.parse(parser);
  } else if (IGNORE_FAILURE_FIELD.match(currentFieldName; parser.getDeprecationHandler())) {
  ignoreFailure = parser.booleanValue();
  } else {
  throw new ParsingException(parser.getTokenLocation(); "Unknown key for a " + token + " in [" + currentFieldName
  + "]."; parser.getTokenLocation());
  } else if (token == XContentParser.Token.START_OBJECT) {
  if (SCRIPT_FIELD.match(currentFieldName; parser.getDeprecationHandler())) {
  script = Script.parse(parser);

Related issues to this log

We have gathered selected Q&A from the community and issues from Github, that can help fix related issues please review the following for further information :

1 elasticsearch 5: Unknown key for a START_OBJECT in [filters] -views 38,052 ,score 19

Unknown key for a START_OBJECT in [simple_query_string] -views   2,211,score 1

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