Quoting "wiki.postgresql.org/wiki/Alter_column_position"
:
"The idea of allowing re-ordering of column position is not one the postgresql developers are against, it is more a case where no one has stepped forward to do the work."
Well, a hard journey starts with a single step.
Why not, in the next release that requires to run initdb, add a
attraw column (a better name is welcome) in the catalog that stores the physical position of column forever, i.e., the same semantics of
attnum?
Then, in a future release - 9.1 for example - the postgres team can make
attnum changeable using something like ALTER COLUMN POSITION?
Pros:
- Requires only a couple of changes in main postgreSQL code. It seems to be very simple.
- Allows a smooth and decentralized rewrite of the whole code that may needs the
attraw attribute - postgreSQL, contribs, pgAdmin, drivers, tools etc.
This will give time to developers of that code to detect the impact of semantics change, make the arrangements necessary and also allow the release of production level software using the new feature before attnum becomes changeable.
So, when
attnum becomes read/write, all that software will be ready.
Cons
- More 4 bytes in each row of the catalog.
Nilson
