Re: A simple question about text fields

On Fri, 2021-06-18 at 10:28 +1000, Gavan Schneider wrote:
> On 18 Jun 2021, at 9:34, David G. Johnston wrote:
> > On Thursday, June 17, 2021, Gavan Schneider <list(dot)pg(dot)gavan(at)pendari(dot)org> wrote:
> >
> > > My approach is to define such fields as ‘text’ and set a constraint using
> > > char_length(). This allows PG to do the business with the text in native
> > > form, and only imposes the cost of any length check when the field is
> > > updated… best of both worlds.
> > >
> >
> > Those are basically the same world…your alternative probably is strictly
> > worse than varchar(n) because of its novel way of implementing the same
> > functionality.
>
> Not sure if this is strictly true. Novelty per se is not always worse. :)

True in general, but not in this case.

There is no advantage in a "text" with a check constraint on the length,
that is, no added functionality.

And it is worse for these reasons:

- the performance will be worse (big reason)

- the length limit is less obvious if you look at the table definition
(small reason)

Yours,
Laurenz Albe
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