On Wednesday, March 26, 2025, Tom Lane <t...@sss.pgh.pa.us> wrote: > jian he <jian.universal...@gmail.com> writes: > > the attached patch is to implement $subject. > > Why would this be a good idea? I don't see any principled fallback > definition of the column. (No, "NULL" is not that.) Certainly we > should support ALTER TABLE DROP COLUMN, but removing the expression > and not providing a substitute seems semantically nonsensical. >
I don’t follow how NULL got involved in this discussion. The proposal is basically: turn the virtual expression into an equivalent stored expression, then drop the expression. I suppose it would make sense to first add an alter table command to allow the user to do a virtual/stored mode swap manually before adding this, which then just becomes a convenient way to specify swap-and-drop as a single command. David J.
