Horton

further clarification: alter table alter column set not null - table scan is skipped

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Cc: psy2000usa@yahoo.com
Date: 2025-07-30T04:52:16Z
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Page: https://www.postgresql.org/docs/17/docguide.html
Description:

Hello there,
I like PostgreSQL a lot so this is my way of giving back.

The "table scan is skipped" optimization can use some clarification
https://www.postgresql.org/docs/current/sql-altertable.html#SQL-ALTERTABLE-DESC-SET-DROP-NOT-NULL
My proposal is "then the table scan is skipped if the alter statement
doesn't drop the constraint."

The reason behind the proposal is documented here
https://dev.to/andrewpsy/the-set-not-null-downtime-trap-in-postgresql-1o71

Thank you for working on such an awesome project.
Cheers,
Andrew

Commits

  1. doc: mention unusability of dropped CHECK to verify NOT NULL