Andreas,I must have missed that, can't find it in hackers?!?
On Wed, 2003-11-19 at 13:07, Andreas Pflug wrote:
Dave Cramer wrote:
Andreas,Why should ALTER COLUMN change the column number, i.e. position?
The point of this is to maintain the column position. I don't think that an alter of a column type should move the column position.
Rod's current proposed patch does that if you do an alter column alter
type. This is an artifact of the underlying mechanism. (ren old col, add
new col, update newcol=oldcol::newtype).
In this case the old attnum value should simply be reused, to retain the original ordering. IMHO this is necessary to prevent problems with any object referencing a column (index, view, ...) The current proposal invents the attpos for column ordering purpose only, but views/indexes/etc will reference attnum, and would need updates.
Actually, a column that changes its attnum is just like a table changing its oid, i.e. it's not the same object any more. This will provoke problems in administration tools (at least in pgAdmin3, which will try to refresh its display with the formerly known oid/attnum af ter executing a change), and maybe other places too.
To put it differently: a ALTER COLUMN command may never-ever change the identifier of the column, i.e. attrelid/attnum.
Regards, Andreas
---------------------------(end of broadcast)--------------------------- TIP 9: the planner will ignore your desire to choose an index scan if your joining column's datatypes do not match
