Am Freitag, den 24.03.2017, 19:32 +0100 schrieb Michael Banck: > On Thu, Mar 23, 2017 at 12:41:54PM +0100, Magnus Hagander wrote: > > On Tue, Mar 21, 2017 at 8:34 PM, Robert Haas <robertmhaas@gmail.com> wrote: > > > So I tend to think that there should always be some explicit user > > > action to cause the creation of a slot, like --create-slot-if-needed > > > or --create-slot=name. That still won't prevent careless use of that > > > option but it's less dangerous than assuming that a user who refers to > > > a nonexistent slot intended to create it when, perhaps, they just > > > typo'd it. > > > > Well, the explicit user action would be "--slot". But sure, I can > > definitely live with a --create-if-not-exists. > > Can we just make that option create slot and don't worry if one exists > already? CreateReplicationSlot() can be told to not mind about already > existing slots, and I don't see a huge point in erroring out if the slot > exists already, unless somebody can show that this leads to data loss > somehow. > > > The important thing, to me, is that you can run it as a single > > command, which makes it a lot easier to work with. (And not like we > > currently have for pg_receivewal which requires a separate command to > > create the slot) > > Oh, that is how it works with pg_receivewal, I have to admit I've never > used it so was a bit confused about this when I read its code. > > So in that case I think we don't necessarily need to have the same user > interface at all. I first thought about just adding "-C, --create" (as > in "--create --slot=foo"), but this on second thought this looked a bit > shortsighted - who knows what flashy thing pg_basebackup might create in > 5 years... So I settled on --create-slot, which is only slightly more to > type (albeit repetive, "--create-slot --slot=foo"), but adding a short > option "-C" would be fine I thinkg "-C -S foo". > > So attached is a patch with adds that option. If people really think it > should be --create-slot-if-not-exists instead I can update the patch, of > course. > > I again added a second patch with some further refactoring which makes > it print a message on temporary slot creation in verbose mode.
Rebased, squashed and slighly edited version attached. I've added this to the 2017-07 commitfest now as well: