Pavel Stehule <pavel.stehule@gmail.com> wrote:
> I would to repeatably update non indexed column of temp table. I
> expected cheap operation, but it isn't true.
You're updating the row 100000 times within a single transaction. I
don't *think* HOT will reclaim a version of a row until the
transaction which completed it is done and no other transactions can
see that version any longer. It does raise the question, though --
couldn't a HOT update of a tuple *which was written by the same
transaction* do an "update in place"? I mean, the updating
transaction doesn't need to see the old row after this, and other
transactions shouldn't see it either.
I suspect that somewhere in the subtransaction or referential
integrity areas there may be some issues with that, but it would be
a clever optimization if it could be pulled off.
-Kevin