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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