Updating index compound format from to – How to solve this Elasticsearch error

Opster Team

Aug-23, Version: 2.3-2.3

Briefly, this error occurs when there’s an attempt to update the compound file format of an Elasticsearch index. This could be due to a version upgrade or a configuration change. The compound format affects how Elasticsearch stores its index files. To resolve this, ensure you’re using a compatible Elasticsearch version for the desired compound format. Also, check your index settings and configurations. If the issue persists, consider reindexing your data with the correct settings.

This guide will help you check for common problems that cause the log ” updating index.compound_format from [{}] to [{}] ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: index, merge and shard.

Log Context

Log “updating index.compound_format from [{}] to [{}]” classname is MergePolicyConfig.java.
We extracted the following from Elasticsearch source code for those seeking an in-depth context :


        double noCFSRatio = parseNoCFSRatio(settings.get(INDEX_COMPOUND_FORMAT; Double.toString(MergePolicyConfig.this.noCFSRatio)));
        if (noCFSRatio != MergePolicyConfig.this.noCFSRatio) {
            logger.info("updating index.compound_format from [{}] to [{}]"; formatNoCFSRatio(MergePolicyConfig.this.noCFSRatio); formatNoCFSRatio(noCFSRatio));
            MergePolicyConfig.this.noCFSRatio = noCFSRatio;


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