Re: Comment - uniqueness of relfilenode

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.

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
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