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Inconsistent behavior with COMPUTED BY fields and metadata extraction [CORE3926] #4261

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firebird-automations opened this issue Sep 17, 2012 · 1 comment

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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.

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