Note that ALTER TABLE cannot alter generated stored columns

Started by Emre Hasegeliover 5 years ago4 messagesdocs
Beta feature

Hackorum builds and tests every patch posted to the lists, not only commitfest submissions. This is Hackorum's own CI rather than the PostgreSQL project's, and it is still under testing - please report anything that looks wrong.

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You can run a PostgreSQL built from this patch straight from Docker, with no checkout and no build:

docker run --rm -p 5432:5432 ghcr.io/hackorum-dev/postgres-patch:t77005
psql -h localhost -U postgres

Built from patchset v1 (message #1), September 20, 2026 at 07:58 AM.

Every patchset is also pushed to a branch of our PostgreSQL fork, so you can check out the same tree CI built. Without a PostgreSQL checkout:

git clone --branch t77005_1 https://github.com/hackorum-dev/postgres.git

In a checkout you already have, add the fork once:

git remote add hackorum https://github.com/hackorum-dev/postgres.git

then, for this patchset and every later one:

git fetch hackorum t77005_1 && git checkout t77005_1

Patchset v1 (message #1) is on t77005_1

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#1Emre Hasegeli
emre@hasegeli.com

I was trying to change the generation expression of a generated stored
column using ALTER TABLE. It took me a while before I figured SET
GENERATED applies only to generated identity columns. I think it'd be
useful to note this in the documentation with something like the
attached.

Attachments:

t77005_1
0001-doc-Note-that-ALTER-TABLE-cannot-alter-generated-sto.patchapplication/octet-stream; name=0001-doc-Note-that-ALTER-TABLE-cannot-alter-generated-sto.patchDownload+8-1
#2Laurenz Albe
laurenz.albe@cybertec.at
In reply to: Emre Hasegeli (#1)
Re: Note that ALTER TABLE cannot alter generated stored columns

On Sun, 2021-05-30 at 16:25 +0300, Emre Hasegeli wrote:

I was trying to change the generation expression of a generated stored
column using ALTER TABLE. It took me a while before I figured SET
GENERATED applies only to generated identity columns. I think it'd be
useful to note this in the documentation with something like the
attached.

+1

Yours,
Laurenz Albe

#3Peter Eisentraut
peter_e@gmx.net
In reply to: Emre Hasegeli (#1)
Re: Note that ALTER TABLE cannot alter generated stored columns

On 30.05.21 15:25, Emre Hasegeli wrote:

I was trying to change the generation expression of a generated stored
column using ALTER TABLE. It took me a while before I figured SET
GENERATED applies only to generated identity columns. I think it'd be
useful to note this in the documentation with something like the
attached.

I don't follow why you put this documentation under ALTER TABLE ... DROP
EXPRESSION. That action doesn't seem related to what you were hoping to do.

#4Emre Hasegeli
emre@hasegeli.com
In reply to: Peter Eisentraut (#3)
Re: Note that ALTER TABLE cannot alter generated stored columns

I don't follow why you put this documentation under ALTER TABLE ... DROP
EXPRESSION. That action doesn't seem related to what you were hoping to do.

I thought that's where it would be if we had ADD/SET EXPRESSION
statements, just like the ADD/SET GENERATED statements just below.