|From:||Kyotaro HORIGUCHI <horiguchi(dot)kyotaro(at)lab(dot)ntt(dot)co(dot)jp>|
|Cc:||andres(at)2ndquadrant(dot)com, robertmhaas(at)gmail(dot)com, tgl(at)sss(dot)pgh(dot)pa(dot)us, pgsql-hackers(at)postgresql(dot)org|
|Subject:||Re: How about to have relnamespace and relrole?|
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Hello, I attached the latest patches missing in the previous mail.
Thanks for pointing Jeevan.
Jim> BTW, I think the potential for MVCC issues should be mentioned in the
Jim> docs (http://www.postgresql.org/docs/devel/static/datatype-oid.html).
The first patch of the aboves contains doc patch which adds the
following note to html/datatype-oid.html. Does it make sense?
> Note: The OID alias types don't sctrictly comply the transaction
> isolation rules so do not use them where exact transaction
> isolation on the values of these types has a
> significance. Likewise, since they look as simple constants to
> planner so you might get slower plans than the queries joining
> the system tables correnspond to the OID types.
At Mon, 2 Mar 2015 17:50:37 -0600, Jim Nasby <Jim(dot)Nasby(at)BlueTreble(dot)com> wrote in <54F4F74D(dot)8000003(at)BlueTreble(dot)com>
> On 3/2/15 3:56 PM, Andres Freund wrote:
> > On 2015-03-02 16:42:35 -0500, Robert Haas wrote:
> >> >On Tue, Feb 3, 2015 at 10:12 AM, Tom Lane<tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> >>> > >Two reasons this isn't terribly compelling are (1) it's creating a
> >>> > >join in a place where the planner can't possibly see it and optimize
> >>> > >it, and (2) you risk MVCC anomalies because the reg* output routines
> >>> > >would not be using the same snapshot as the calling query.
> >>> > >
> >>> > >We already have problem (2) with the existing reg* functions so I'm
> >>> > >not that excited about doubling down on the concept.
> >> >
> >> >I think I agree. I mean, I agree that this notation is more
> >> >convenient, but I don't really want to add a whole new slough of types
> >> >--- these will certainly not be the only ones we want once we go down
> >> >this path --- to the default install just for notational convenience.
> >> >It's arguable, of course, but I guess I'm going to vote against this
> >> >patch.
> > That's a justifyable position. I don't think there are other catalogs
> > referenced as pervasively in the catalog though.
> > There's one additional point: Using reg* types in the catalog tables
> > themselves can make them*much* easier to read. I personally do look at
> > the catalogs a awful lot, and seing names instead of oids makes it
> > much
> > easier. And adding regtype/role would allow to cover nearly all types
> > containing oids.
> +1. Constantly joining catalog tables together is a royal PITA, and
> regnamespace is the biggest missing part of this (I typically don't
> look at roles too much, but I can certainly see it's importance).
> If we had more user friendly views on the catalogs maybe this wouldn't
> be an issue... but that's a much larger project.
> BTW, I think the potential for MVCC issues should be mentioned in the
> docs (http://www.postgresql.org/docs/devel/static/datatype-oid.html).
NTT Open Source Software Center
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