Inconsistent behavior with COMPUTED BY fields and metadata extraction [CORE3926]

[firebird-automations]

Submitted by: @WarmBooter

ALTER statement allows me to change a computed by field with a new formula referencing a field that is positioned higher than the computed by field, but when you extract the table metadata and try to run it, it crashes with "Column unknown." error.

To reproduce:

Step 1)

create table a ( field2 numeric (9,2), field1 computed by (field2 * 0.5));

Step 2)

alter table a add field3 numeric (9,2);

Step 3)

alter table a alter field1 computed by (field3 * 0.5); -- This works fine!!!

Step 3 works fine, but when you extract the DDL of the table and try to run it, it will crash, since it will be extracted like:

CREATE TABLE A ( FIELD2 NUMERIC(9,2), FIELD1 COMPUTED BY (field3 * 0.5), FIELD3 NUMERIC(9,2) );

This means that you may have a "good" database, but when you extract its metadata into a script to create another empty database, it will crash :-(

IMHO, the behavior should be consistent in the two scenarios so, or the table creation should succeed, or the ALTER should had failed.

[firebird-automations]

Commented by: @mrotteveel

In my opinion the alter should never fail, that would be too inflexible IMHO.