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MyISAM Performance Regression Since 8.0.12 With Table Scans (Doc ID 2992586.1)

Last updated on DECEMBER 12, 2023

Applies to:

MySQL Server - Version 8.0 and later
Information in this document applies to any platform.

Symptoms

For queries that read a lot of data from MyISAM tables (*.MYD),  such as table scans,   there are performance regressions of magnitudes (about 20x slower).
The issue began in 8.0.12.

Changes

 Upgrading from 5.5, 5.6, 5.7 to a version after 8.0.12 shows this regression.  No other changes in data or queries or optimizer plans.

Cause

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In this Document
Symptoms
Changes
Cause
Solution
References


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