=?utf-8?q?PG_Doc_comments_form?= <noreply(at)postgresql(dot)org> writes:
> What does a table rewrite do? Does it drop and recreate the table?
> Everywhere I look people describe it with fear and trepedation as if it was
> some catastrophically dangerous operation to perform. What is it?
It means reading the whole table and writing it out in some modified
form (for instance, with some column transformed into a new datatype).
It's not "dangerous" in any way ... but if you've got many GB of data in
the table and you can't afford to have the table locked for a long time,
then it's something to avoid.
regards, tom lane