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8.0.18 to 8.0.20 Shows Performance Regression of SELECT DISTINCT (Doc ID 2613353.1)

Last updated on MAY 11, 2020

Applies to:

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

Symptoms

 The symptom can be seen in queries like this,   who process a large number of rows with many duplicates:

  SELECT DISTINCT a,b,c,d,e,f,g,h,i,j FROM t;

 

8.0.18 takes around 5x longer than 8.0.17 and earlier versions.

 

Changes

8.0.18, 8.0.19, or 8.0.20 was installed.

Cause

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In this Document
Symptoms
Changes
Cause
Solution
References

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