Re: Backend-internal SPI operations

Tom Lane wrote:
> "Mark Hollomon" <mhh@nortelnetworks.com> writes:
> > Just out of curiousity, is there technical reason there isn't
> > a (say) relisview attribute to pg_class?
>
> That might indeed be the most reasonable way to attack it, rather
> than having to go messing about looking for a matching rule.
> (Jan, any thoughts here?)

    The  right  way  IMHO would be to give views another relkind.
    Then we could easily

    1.  detect if the final query after rewriting still tries  to
        INSERT/UPDATE/DELETE  a  view  -  i.e.  "missing  rewrite
        rule(s)".

    2.  disable things like LOCK etc.

    The problem here is, that the relkind  must  change  at  rule
    creation/drop  time.  Fortunately rules on SELECT are totally
    restricted to VIEW's since 6.4, and I don't see any reason to
    change this.

    And  it's time to make more use of the relkind attribute. For
    7.2, when we want to have tuple-set returns for functions, we
    might  want  to have structures as well (we talked about that
    already, Tom). A structure is just a row/type description.  A
    function, returning a tuple or set of tuples, can return this
    type or set of type as well as any other existing  table/view
    structure. So to create a function returning a set of tuples,
    which have a structure different  from  any  existing  table,
    someone   creates   a  named  structure,  then  the  function
    returning tuples of that type.   These  structures  are  just
    entries  in  pg_class, pg_attribute and pg_type.  There is no
    file or any rules, triggers etc. attached to them. They  just
    describe a typle that can be built in memory.

> Adding a column to a core system table like pg_class is a good
> exercise for the student ;-) ... it's not exactly automated,
> and you have to find all the places that need to be updated.
> You might want to keep notes and prepare a writeup for the
> developer's FAQ.  I thought of that the last time I did something
> similar, but it was only at the end that I realized I should've
> been keeping notes to start with.

    Meetoo :-}


Jan

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