Re: [GENERAL] do delete/insert instead of update if name changes

amy cheng wrote:
>
> hi, all experts there,
>
> I'm studying the example in postgresql-6.5.1/src/pl/plpgsql/test.
> I do not understand why we need "do delete/insert instead of update if name
> changes". Is it ONLY for the test, or, there is some
> reason for doing that in practical use?
>
> I cut/paste part of it below.
>
iirc, slotname is the primary key, and an update on a primary key might
be a "bad thing"
- e.g. I dunno if when changing only the key field, the index is updated
automagically -
so maybe a proper INSERT statement is the right way to do it.

> amy
> ########################################
> -- ************************************************************
> -- * BEFORE UPDATE on PHone
> -- *    - do delete/insert instead of update if name changes
> -- ************************************************************
> create function tg_phone_bu() returns opaque as '
> begin
>     if new.slotname != old.slotname then
>         delete from PHone where slotname = old.slotname;
>         insert into PHone (
>                     slotname,
>                     comment,
>                     slotlink
>                 ) values (
>                     new.slotname,
>                     new.comment,
>                     new.slotlink
>                 );
>         return null;
>     end if;
>     return new;
> end;
> ' language 'plpgsql';
>
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