Altering parent table breaks child table defaults

Hi all,

This problem has also been posted to Stack Overflow. http://stackoverflow.com/questions/19227920/altering-a-parent-table-in-postgresql-8-4-breaks-child-table-defaults

The problem: In Postgresql 8.4 (not tested on other versions), if table `temp_person_two` inherits from`temp_person`, default column values on the child table are ignored if the *parent* table is altered.

How to replicate (these don't need to be temporary tables. I made them temporary for your cut-n-paste convenience):

First, create table and a child table. The child table should have one column that has a default value.

    CREATE TEMPORARY TABLE temp_person (
        person_id SERIAL,
        name      VARCHAR
    );

    CREATE TEMPORARY TABLE temp_person_two (
        has_default character varying(4) DEFAULT 'en'::character varying NOT NULL
    ) INHERITS (temp_person);

Next, create a trigger on the parent table that copies its data to the child table (I know this appears like bad design, but this is a minimal test case to show the problem).

    CREATE FUNCTION temp_person_insert() RETURNS trigger
    LANGUAGE plpgsql
    AS '
    BEGIN
    INSERT INTO temp_person_two VALUES ( NEW.* );
    RETURN NULL;
    END;
    ';

    CREATE TRIGGER temp_person_insert_trigger
        BEFORE INSERT ON temp_person
        FOR EACH ROW
        EXECUTE PROCEDURE temp_person_insert();

Then insert data into parent and select data from child. The data should be correct.

    INSERT INTO temp_person (name) VALUES ('ovid');
    SELECT * FROM temp_person_two;
     person_id | name | has_default
    -----------+------+-------------
             1 | ovid | en
    (1 row )

Finally, alter the parent table by adding a new, unrelated column. Attempt to insert data and watch a "not-null constraint" violation occur:

    ALTER TABLE temp_person ADD column foo text;
    INSERT INTO temp_person(name) VALUES ('Corinna');
    ERROR:  null value in column "has_default" violates not-null constraint
    CONTEXT:  SQL statement "INSERT INTO temp_person_two VALUES (  $1 .* )"
    PL/pgSQL function "temp_person_insert" line 2 at SQL statement

My version:

    testing=# select version();
                                                    version
    -------------------------------------------------------------------------------------------------------
     PostgreSQL 8.4.17 on x86_64-pc-linux-gnu, compiled by GCC gcc-4.4.real (Debian 4.4.5-8) 4.4.5, 64-bit
    (1 row)

Cheers,
Ovid 
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