Re: [HACKERS] Upgrading (was: now 6.4)

> 
>    I hate to open a potential can of worms here, but here's another
> possibility.  I recall someone telling me about a database (InterBase,
> I believe it was) that could have rows with different structures all
> in the same table.  In other words, they could add a field to the
> table, and any new rows would have it, while the old ones would not,
> and the database would deal with it on the fly.
>    Could we implement some type of "version" field in the table
> structure which would allow this type of thing?  If this is
> reasonable, we could have it in 6.4 and potentially never have to
> worry too much about reloading tables after that.  With version info
> in each tuple, we could convert the table "as we go" or in some other
> gradual way.
>    Of course, the question of how much work it would take to have the
> backend support this needs to be considered, as well as the issue of
> how this would impact performance.

Actually, we already have that.  When you add a column to a table, it
does not re-structure the old rows.  However, system tables do not
always add columns.  Sometimes we change them.  Also there is lots
more/different rows for tables, and keeping that straight would be
terrible.

If we can keep the original data files and require initdb and a
re-index, that would be good.

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