Bug Report

Summary

As reported #5661

When creating generated column using columnDefinition , the schema tool will try to generate a `ALTER TABLE mytable ALTER mycolumn DROP DEFAULT

the reason is that currently PostgreSQLSchemaManager considers SELECT pg_get_expr(adbin, adrelid) FROM pg_attrdef as containing ONLY the attribute DEFault value , while it contains the attribute DEFinition , which is 99% of the time the default value .... except for generated column

for a column defined as foobar INT GENERATED ALWAYS AS ( otherColumn / 100 ) STORED , SELECT pg_get_expr(adbin, adrelid) FROM pg_attrdef will return the part inside () i.e otherColumn / 100 , i.e the definition of the generated value.

Current behaviour

Currently ColumnDiff will always see a change because the schema definition says there's no default which is correct as 'default' as no meaning for a , while PostgreSQLSchemaManager will report the column as having

How to reproduce

CREATE SEQUENCE fulltext_id_seq INCREMENT BY 1 MINVALUE 1 START 1;
CREATE TABLE fulltext (
id INT NOT NULL, column1 TEXT DEFAULT NULL, 
column2 TEXT DEFAULT NULL,
concatenated  TEXT GENERATED ALWAYS AS  ( column1 || column 2 )  STORED,
PRIMARY KEY(id)
);

* Add the below entity in your (Symfony) codebase. Outside Symfony, change the command to orm:schema-tool:update. The point is to get the SchemaTool to try to detect changes.
* Run bin/console do:sch:up --force to create the table and sequence
* Run bin/console do:sch:up --dump-sql to see the broken update queries.

<?php

namespace App\Entity;

use Doctrine\ORM\Mapping as ORM;

#[ORM\Entity]
class Fulltext
{
    #[ORM\Id]
    #[ORM\GeneratedValue]
    #[ORM\Column(type: 'integer')]
    private $id;
    
    #[ORM\Column(type: 'text', nullable: true)]
    private $column1;

    #[ORM\Column(type: 'text', nullable: true)]
    private $column2;

    #[ORM\Column(
        type: 'text',
        nullable: true,
        insertable: false,
        updatable: false,
        columnDefinition: "TEXT GENERATED ALWAYS AS (  column1 || column2 )   STORED",
        generated: 'ALWAYS',
    )]
    private $concatenated;
}

it will try to generate the diff

`ALTER TABLE fulltext  ALTER concatenated DROP DEFAULT

Expected behaviour

it should not see a difference

I will open a PR as I have a fix which I think is not hackish