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# Technical Advisory 71553

Publication date: November 8, 2021

## Description

Secondary unique indexes that are created as a result of running two `ALTER PRIMARY KEY` statements on the same table can be misinterpreted by the vectorized engine, potentially creating incorrect results. Precisely, if you create a new primary key with `ALTER PRIMARY KEY`, and then edit the primary key again with a second `ALTER PRIMARY KEY`, the secondary unique index that was the primary key created by the first `ALTER PRIMARY KEY` statement will be affected by this issue.

CockroachDB versions 20.2 and 21.1 are affected by this bug, until maintenance versions 20.2.18 and 21.1.12.

## Statement

This bug was resolved by a fix in CockroachDB which corrects the bug in the vectorized engine that caused the database to return incorrect results when reading unique secondary indexes that were created as a result of an `ALTER PRIMARY KEY`.

The fix has been applied to maintenance versions 20.2.18 and 21.1.12 of CockroachDB.

## Mitigation

Users of CockroachDB are encouraged to upgrade to a maintenance version with the fix applied.

To work around the issue without upgrading, you can:

* Rebuild any unique secondary indexes created as a result of an `ALTER PRIMARY KEY` statement, using `DROP INDEX` and `CREATE INDEX`.
* Temporarily disable the vectorized engine by running `SET CLUSTER SETTING sql.defaults.vectorize = off`.

## Impact

SQL statements that used secondary unique indexes that were created as a result of an `ALTER PRIMARY KEY` statement can return incorrect results.

Please reach out to the [support team](https://support.cockroachlabs.com/) if you need more information or assistance.