Re: [PATCH] proposal for regexp_count, regexp_instr, regexp_substr and regexp_replace

Gilles Darold <gillesdarold@gmail.com> writes:
> [ v4-0001-regexp-foo-functions.patch ]

I started to work through this and was distressed to realize that
it's trying to redefine regexp_replace() in an incompatible way.
We already have

regression=# \df regexp_replace
                               List of functions
   Schema   |      Name      | Result data type |  Argument data types   | Type
------------+----------------+------------------+------------------------+------
 pg_catalog | regexp_replace | text             | text, text, text       | func
 pg_catalog | regexp_replace | text             | text, text, text, text | func
(2 rows)

The patch proposes to add (among other alternatives)

+{ oid => '9608', descr => 'replace text using regexp',
+  proname => 'regexp_replace', prorettype => 'text',
+  proargtypes => 'text text text int4', prosrc => 'textregexreplace_extended_no_occurrence' },

which is going to be impossibly confusing for both humans and machines.
I don't think we should go there.  Even if you managed to construct
examples that didn't result in "ambiguous function" failures, that
doesn't mean that ordinary mortals won't get bit that way.

I'm inclined to just drop the regexp_replace additions.  I don't think
that the extra parameters Oracle provides here are especially useful.
They're definitely not useful enough to justify creating compatibility
hazards for.

            regards, tom lane