Re: [HACKERS] 'a' == 'a '

Dann,

> I think that whatever is done ought to be whatever the standard says.
> If I misinterpret the standard and PostgreSQL is doing it right, then
> that is fine.  It is just that PostgreSQL is very counter-intuitive
> compared to other database systems that I have used in this one
> particular area.  When I read the standard, it looked to me like
> PostgreSQL was not performing correctly.  It is not unlikely that I read
> it wrong.

AFAIT, the standard says "implementation-specific". So we're standard.

The main cost for comparing trimmed values is performance; factoring an
rtrim into every comparison will add significant overhead to the already
CPU-locked process of, for example, creating indexes. We're looking for
ways to make the comparison operators lighter-weight, not heavier.

My general perspective on this is that if trailing blanks are a significant
hazard for your application, then trim them on data input. That requires
a *lot* less peformance overhead than doing it every time you compare
something.

Changing the behaviour would break backwards compatibility for some users.
For that matter, I've been subscribed to 8 PostgreSQL mailing lists since
1999, and this is the first time I can recall someone complaining about
this comparison behavior. So it's obviously not a widespread issue.

--
--Josh

Josh Berkus
Aglio Database Solutions
San Francisco