+1 for AS DEFAULT syntax if it helps in improving readability specially in following case
CREATE TABLE p1 PARTITION OF test AS DEFAULT PARTITION BY LIST(a); Thank you, Rahila Syed On Tue, May 9, 2017 at 1:13 AM, Robert Haas <robertmh...@gmail.com> wrote: > On Thu, May 4, 2017 at 4:40 PM, Sven R. Kunze <srku...@mail.de> wrote: > > It yields > > > > CREATE TABLE p1 PARTITION OF test DEFAULT PARTITION BY LIST(b); > > > > This reads to me like "DEFAULT PARTITION". > > > > I can imagine a lot of confusion when those queries are encountered in > the > > wild. I know this thread is about creating a default partition but I > were to > > propose a minor change in the following direction, I think confusion > would > > be greatly avoided: > > > > CREATE TABLE p1 PARTITION OF test AS DEFAULT PARTITIONED BY LIST(b); > > > > I know it's a bit longer but I think those 4 characters might serve > > readability in the long term. It was especially confusing to see > PARTITION > > in two positions serving two different functions. > > Well, we certainly can't make that change just for default partitions. > I mean, that would be non-orthogonal, right? You can't say that the > way to subpartition is to write "PARTITION BY strategy" when the table > unpartitioned or is a non-default partition but "PARTITIONED BY > strategy" when it is a default partition. That would certainly not be > a good way of confusing users less, and would probably result in a > variety of special cases in places like ruleutils.c or pg_dump, plus > some weasel-wording in the documentation. We COULD do a general > change from "CREATE TABLE table_name PARTITION BY strategy" to "CREATE > TABLE table_name PARTITIONED BY strategy". I don't have any > particular arguments against that except that the current syntax is > more like Oracle, which might count for something, and maybe the fact > that we're a month after feature freeze. Still, if we want to change > that, now would be the time; but I favor leaving it alone. > > I don't have a big objection to adding AS. If that's the majority > vote, fine; if not, that's OK, too. I can see it might be a bit more > clear in the case you mention, but it might also just be a noise word > that we don't really need. There don't seem to be many uses of AS > that would pose a risk of actual grammar conflicts here. I can > imagine someone wanting to use CREATE TABLE ... PARTITION BY ... AS > SELECT ... to create and populate a partition in one command, but that > wouldn't be a conflict because it'd have to go AFTER the partition > specification. In the DEFAULT case, you'd end up with something like > > CREATE TABLE p1 PARTITION OF test AS DEFAULT AS <query> > > ...which is neither great nor horrible syntax-wise and maybe not such > a good thing to support anyway since it would have to lock the parent > to add the partition and then keep the lock on the parent while > populating the new child (ouch). > > So I guess I'm still in favor of the CREATE TABLE p1 PARTITION OF test > DEFAULT syntax, but if it ends up being AS DEFAULT instead, I can live > with that. > > Other opinions? > > -- > Robert Haas > EnterpriseDB: http://www.enterprisedb.com > The Enterprise PostgreSQL Company >
