Re: record identical operator

Kevin,

On Wednesday, September 18, 2013, Kevin Grittner wrote:

> Stephen Frost <sfrost(at)snowman(dot)net <javascript:;>> wrote:
>
> > If it's not actually *changing* (wrt its value), then I'm not at
> > all impressed with the notion that it's going to get updated
> > anyway.
>
> But PostgreSQL very specifically (and as far as I can tell
> *intentionally*) allows you to *change* a value and have it still
> be considered *equal*.

I'm curious where you're going with that- of course you can update a value
and have the same value (and possibly the same byte representation) stored
over the old.

> The concept of equal values really means
> more like "equivalent" or "close enough" for common purposes. It
> very specifically does *not* mean the same value.

I'm really curious about your thoughts on unique indexes then. Should two
numerics which are the same value but different byte representations be
allowed in a unique index?

> As just one example, think how much easier the citext type would be
> to implement if it folded all values to lower case as they were
> input, rather than preserving the data as entered and considering
> different capitalizations as "equal".

If the type operator says they're equal, then I think we need to consider
them as equal. If an update happens with a conditional of:

where col1 = 'Abc'

When col1 is 'ABC' using citext, should we still issue the update?

The notion that in PostgreSQL a value has not changed if the new
> value is equal to the old is just flat out wrong.

The value *can* be changed to be equal to the existing value but that
doesn't make the two values *not equal*.

Thanks,

Stephen