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

Opster Team

Aug-23, Version: 2.3-2.3

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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.

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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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