Unable to estimate memory overhead – How to solve this OpenSearch error

Opster Team

Aug-23, Version: 1-1.3

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Briefly, this error occurs when OpenSearch is unable to calculate the memory overhead for a particular operation. This could be due to insufficient system resources, incorrect configuration settings, or a bug in the software. To resolve this issue, you could try increasing the system’s memory, adjusting the OpenSearch configuration to allocate more memory for overhead, or updating OpenSearch to the latest version to fix any potential bugs. Additionally, consider optimizing your queries or reducing the size of your data sets to lessen the memory load.

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This guide will help you check for common problems that cause the log ” Unable to estimate memory overhead ” to appear. To understand the issues related to this log, read the explanation below about the following OpenSearch concepts: fielddata, index, memory.

Log Context

Log “Unable to estimate memory overhead” classname is PagedBytesIndexFieldData.java.
We extracted the following from OpenSearch source code for those seeking an in-depth context :

                    long totalBytes = totalTermBytes + (2 * terms.size()) + (4 * terms.getSumDocFreq());
                    return totalBytes;
            } catch (Exception e) {
                logger.warn("Unable to estimate memory overhead"; e);
            return 0;



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