Re: alter column appears to work, but doesn't?

[Ron Peterson <rpeterso@xxxxxxxxxxxxx>]

2011-09-05_16:14:00-0400 Tom Lane <tgl@xxxxxxxxxxxxx>:
> Ron Peterson <rpeterso@xxxxxxxxxxxxx> writes:
> > I just dropped my logging rules, stopped the database and restarted it,
> > put my rules back in place, and now it works.  Not sure why.  Cached
> > query plan?
> 
> Maybe.  We'd need a reproducible test case to do more than speculate
> though.

Hi Tom,

I was able to reproduce this.  DDL below.  Probably more DDL than
necessary, but not sure what is or isn't relevant.

postgres=# drop rule attribute_insert_rule on attributes;
postgres=# drop rule attribute_update_rule on attributes;
postgres=# drop rule attribute_delete_rule on attributes;
postgres=# alter table attributes_log alter column attribute_name type varchar(50);
...then recreate rules below
postgres=# insert into attributes values ( repeat( 'x', 49 ) );
ERROR:  value too long for type character varying(48)


CREATE TABLE attributes (
  attribute_name
    VARCHAR(48)
    UNIQUE
    NOT NULL
);

-- Attribute names can be inserted or deleted, but not changed.
CREATE OR REPLACE FUNCTION attribute_name_freeze_tf()
RETURNS TRIGGER
AS $$
BEGIN
  IF (TG_OP = 'INSERT') THEN
    IF NEW.attribute_name = OLD.attribute_name THEN
      RETURN NEW;
    END IF;
  END IF;
  RETURN NULL;
END;
$$ LANGUAGE plpgsql;

CREATE TRIGGER attribute_name_freeze_t
BEFORE UPDATE ON attributes
FOR EACH ROW EXECUTE PROCEDURE attribute_name_freeze_tf();

CREATE TABLE attributes_log (
  attribute_name
    VARCHAR(48),
  action
    CHAR(6)
    NOT NULL
    CHECK( action IN ('insert', 'delete','update') ),
  changed
    TIMESTAMP WITH TIME ZONE
    NOT NULL
    DEFAULT CURRENT_TIMESTAMP
);

CREATE RULE attribute_insert_rule AS
ON INSERT TO attributes
DO
(
  INSERT INTO attributes_log (
    attribute_name,
    action )
  VALUES (
    new.attribute_name,
    'insert' );
);

CREATE RULE attribute_update_rule AS
ON UPDATE TO attributes
DO
(
  INSERT INTO attributes_log (
    attribute_name,
    action )
  VALUES (
    new.attribute_name,
    'update' );
);

CREATE RULE attribute_delete_rule AS
ON DELETE TO attributes
DO
(
  INSERT INTO attributes_log (
    attribute_name,
    action )
  VALUES (
    old.attribute_name,
    'delete' );
);
------------------------------------------------------------------------


-- 
Ron Peterson
Network & Systems Administrator
Mount Holyoke College
http://www.mtholyoke.edu/~rpeterso

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