Re: Re: PDF book July 2, 2000 version

Bruce Momjian wrote:
> Can someone comment on this? Why doesn't OID work in foreign keys.
> Seems this is a bug.

The RI triggers check for attribute existance by looking up
in the relations descriptor via SPI_fnumber(). Since OID is a
system attribute, it returns SPI_ERROR_NOATTRIBUTE and that
causes the error.

Later on, I'm not sure that it is possible to use SPI
functions to obtain the OID of a given trigger tuple. So it'd
be a little more to fix it.

Jan

>
> > First off I want to say thank your for creating a sorely needed reference and
> > sharing it with the online world via the PDF document.
> >
> > I do have one minor complaint though. I'm learning Postgres from your book
> > although I'm familiar with the basics of SQL. I was at first excited then
> > discouraged by the OID section of your book. I think a much needed
> > addition to the OID limitations section is that the OID field can not be
> > referenced in a foreign key. IE
> >
> > CREATE TABLE t1( i INTEGER);
> > CREATE TABLE t2( id OID REFERENCES t1(oid));//dose not work
> >
> > You use the OID is a foreign key of sorts in the example, but you never qualify
> > that using the foreign key constraint system in Postgres will not allow you to
> > automate this. I realize the OID section comes long before the constraints
> > chapter, but a quick qualification would still make things clearer. Without
> > the ability to use the OID field as a reference for foreign keys, it's
> > usefulness is very limited.
> >
> > Keep up the good work, I can't wait to buy the finished product!
> >
> > _________________________
> > Richard Rowell
> > rrowell(at)shreve(dot)net
> >
> > Perl is the unix world's equivalent of VB - and just as much of an abomination.
> >
>
>
> --
> Bruce Momjian | http://www.op.net/~candle
> pgman(at)candle(dot)pha(dot)pa(dot)us | (610) 853-3000
> + If your life is a hard drive, | 830 Blythe Avenue
> + Christ can be your backup. | Drexel Hill, Pennsylvania 19026
>

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