Re: Virtual generated columns

Peter Eisentraut <peter@eisentraut.org>

From: Peter Eisentraut <peter@eisentraut.org>

To: jian he <jian.universality@gmail.com>

Cc: pgsql-hackers <pgsql-hackers@postgresql.org>

Date: 2024-07-29T14:59:07Z

Lists: pgsql-hackers

Commits

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Expand virtual generated columns for ALTER COLUMN TYPE
- 5069fef1cfae 18.0 landed
Eliminate code duplication in replace_rte_variables callbacks
- 363a6e8c6fcf 18.0 landed
Expand virtual generated columns in the planner
- 1e4351af329f 18.0 landed
Virtual generated columns
- 83ea6c54025b 18.0 landed
Additional tests for stored generated columns
- 41084409f635 18.0 landed
Improve generated_stored test
- 44b61efb7928 18.0 landed
- 86749ea3b766 18.0 landed
Fix handling of CREATE DOMAIN with GENERATED constraint syntax
- 84a67725cd11 18.0 landed
Add pg_constraint rows for not-null constraints
- 14e87ffa5c54 18.0 cited
Put generated_stored test objects in a schema
- 894be11adfa6 18.0 landed
Rename regress test generated to generated_stored
- b9ed4969250d 18.0 landed
Small code simplification
- 7ff9afbbd1df 18.0 landed
Remove useless code
- e26d313bad92 18.0 landed
Remove useless initializations
- da2aeba8f533 18.0 landed
doc: Clarify that pg_attrdef also stores generation expressions
- da486d360103 18.0 landed
Clean out column-level pg_init_privs entries when dropping tables.
- 76618097a6c0 17.0 cited
Re-implement the ereport() macro using __VA_ARGS__.
- e3a87b4991cc 13.0 cited

On 22.07.24 12:53, jian he wrote:
> another bug?
> drop table gtest12v;
> CREATE TABLE gtest12v (a int PRIMARY KEY, b bigint, c int GENERATED
> ALWAYS AS (b * 2) VIRTUAL);
> insert into gtest12v (a,b) values (11,  22147483647);
> table gtest12v;
> 
> insert ok, but select error:
> ERROR:  integer out of range
> 
> should insert fail?

I think this is the correct behavior.

There has been a previous discussion: 
https://www.postgresql.org/message-id/2e3d5147-16f8-af0f-00ab-4c72cafc896f%402ndquadrant.com

> CREATE TABLE gtest12v (a int PRIMARY KEY, b bigint, c int GENERATED
> ALWAYS AS (b * 2) VIRTUAL);
> CREATE SEQUENCE sequence_testx OWNED BY gtest12v.c;
> 
> seems to work. But I am not sure if there are any corner cases that
> make it not work.
> just want to raise this issue.

I don't think this matters.  You can make a sequence owned by any 
column, even if that column doesn't have a default that invokes the 
sequence.  So nonsensical setups are possible, but they are harmless.