Re: Comment - uniqueness of relfilenode

On Mon, Nov 11, 2013 at 05:48:52PM +0100, Antonin Houska wrote:
> On 11/10/2013 12:57 AM, Robert Haas wrote:
> > On Thu, Nov 7, 2013 at 10:56 AM, Antonin Houska
> > <antonin.houska@gmail.com> wrote:
> >> catalog/catalog.c:GetNewRelFileNode() and its calls indicate that the
> >> following change makes sense:
> >>
> >>
> >> diff --git a/src/include/storage/relfilenode.h
> >> b/src/include/storage/relfilenode.h
> >> index 75f897f..7190974 100644
> >> --- a/src/include/storage/relfilenode.h
> >> +++ b/src/include/storage/relfilenode.h
> >> @@ -55,7 +55,7 @@ typedef enum ForkNumber
> >>   * relNode identifies the specific relation.  relNode corresponds to
> >>   * pg_class.relfilenode (NOT pg_class.oid, because we need to be able
> >>   * to assign new physical files to relations in some situations).
> >> - * Notice that relNode is only unique within a particular database.
> >> + * Notice that relNode is only unique within a particular tablespace.
> >>   *
> >>   * Note: spcNode must be GLOBALTABLESPACE_OID if and only if dbNode is
> >>   * zero.  We support shared relations only in the "global" tablespace.
> >>
> >>
> >> // Antonin Houska (Tony)
> > 
> > Technically speaking, I think it's only guaranteed to be unique with a
> > database-tablespace combination.  In other words, the same OID can be
> > reused as a relfilenode if *either* of those two values differs.
> 
> You're right. I missed the fact that Postgres (unlike another DBMS that
> I worked with) allows for tablespace to be shared across databases.

I have update the C comment:
<  * Notice that relNode is only unique within a particular database.--->  * Notice that relNode is only unique within
aparticular tablespace.
 

--  Bruce Momjian  <bruce@momjian.us>        http://momjian.us EnterpriseDB
http://enterprisedb.com
 + Everyone has their own god. +