Re: Questions about indexes with text_pattern_ops

Gregory Stark <stark@enterprisedb.com> writes:
> "Tom Lane" <tgl@sss.pgh.pa.us> writes:
>> How so?  If you think this change is a bad idea you'd better speak up
>> PDQ.

> Well I think it's fine for 'foo ' != 'foo' even if they sort similarly. 

> But I'm not sure it makes sense for <'foo ','a'> to sort after <'foo','b'> if
> the locale says that 'foo ' should be compare "equal" to 'foo' and 'a' before
> 'b'.

I don't think we can concern ourselves with that; it would require
allowing different columns of an index to interact, which would be
impossibly messy.  What's more, it'd destroy the property that a btree
index is sorted by its leading column(s) as well as by all its columns.

> Perhaps we should always generate those inequalities even if there's no index
> that can use them.

Hmmm ... we intentionally don't do that, but the constraint exclusion
code might be a sufficient reason to reconsider.
        regards, tom lane