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19c: Slow Performance For A Query Caused By Hash unique (Group By) Cardinality Underestimated (Doc ID 3080284.1)

Last updated on APRIL 09, 2025

Applies to:

Oracle Database - Enterprise Edition - Version 19.20.0.0.0 and later
Gen 1 Exadata Cloud at Customer (Oracle Exadata Database Cloud Machine) - Version N/A and later
Gen 2 Exadata Cloud at Customer - Version N/A and later
Information in this document applies to any platform.

Symptoms

A query with an anti-join gets inaccurate cardinality estimate for a HASH UNIQUE operation.

For instance, HASH UNIQUE cardinality is underestimated 1 versus actual 11000.

The join under the HASH UNIQUE step has correct cardinality.

Changes

 N/A

Cause

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In this Document
Symptoms
Changes
Cause
Solution
References


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