Re: CTIDs invalidations and dropping columns.

On Tue, Jul 11, 2006 at 01:50:40AM +0300, Tzahi Fadida wrote:
> As i understand rowids, i.e ctids, are supposed to allow for fast access to
> the tables. I don't see the rational, for example, when casting some
> attributes, to blank the ctid. So it is not exactly the same, but it still
> came from the same tuple. What will happen if for read only SPI queries
> it will not be blank?

Did you read the email Tom sent?

I worked out the exact issue with your example btw. It's because of the
DROP COLUMN. After dropping the column the tuples on disk have 3
columns and you only asked for 2, so an extra step has to be taken.
This extra step copies the two values, creating a new tuple, which has
no CTID.

If you're tying yourself this tightly to the backend, maybe you should
just use index_beginscan/heap_beginscan/etc which return actual tuples.

Have a nice day,
--
Martijn van Oosterhout <kleptog(at)svana(dot)org> http://svana.org/kleptog/
> From each according to his ability. To each according to his ability to litigate.