Iteration order of bucketOrds changed without mutating – How to solve this OpenSearch exception

Opster Team

Aug-23, Version: 1-1.1

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Briefly, this error occurs when the iteration order of bucketOrds, which are used in aggregations in OpenSearch, is altered without any mutation. This could be due to a bug in the code or an unexpected change in the data. To resolve this issue, you can try the following: 1) Review your code to ensure that bucketOrds are being handled correctly. 2) Check your data for any unexpected changes or inconsistencies. 3) Update to the latest version of OpenSearch, as this may contain a fix for the issue. 4) If the problem persists, consider reporting it as a bug to the OpenSearch community.

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This guide will help you check for common problems that cause the log ” Iteration order of [” + bucketOrds + “] changed without mutating. [ ” to appear. To understand the issues related to this log, read the explanation below about the following OpenSearch concepts: aggregations, search.

Log Context

Log “Iteration order of [” + bucketOrds + “] changed without mutating. [” class name is We extracted the following from OpenSearch source code for those seeking an in-depth context :

 for (int ordIdx = 0; ordIdx < owningBucketOrds.length; ordIdx++) {
 List buckets = new ArrayList<>((int) bucketOrds.size());
 LongKeyedBucketOrds.BucketOrdsEnum ordsEnum = bucketOrds.ordsEnum(owningBucketOrds[ordIdx]);
 while( {
 if (bucketOrdsToCollect[b] != ordsEnum.ord()) {
 throw new AggregationExecutionException("Iteration order of [" + bucketOrds + "] changed without mutating. ["
 + ordsEnum.ord() + "] should have been [" + bucketOrdsToCollect[b] + "]");
 buckets.add(; bucketDocCount(ordsEnum.ord()); subAggregationResults[b++]));
 results[ordIdx] =[ordIdx]; buckets);


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