Re: add function argument name to substring and substr

On Tue, Feb 18, 2025 at 6:13 AM David G. Johnston
<david(dot)g(dot)johnston(at)gmail(dot)com> wrote:
>
> Table 9.9 limits itself to those functions defined in the SQL standard; which are basically the ones that use keywords instead of commas.
>
> The substring(string, start, count) function you note is already covered in Table 9.10 but we spell it substr(...)
>
> I don't think adding yet more spellings of this same function is warranted or desirable at this point.

ok.

> I'd maybe add a note if substring(,,,) works to substr saying that substring is a valid alias. I could be convinced to just document though.
>
it seems already in the doc.

substr ( string text, start integer [, count integer ] ) → text
Extracts the substring of string starting at the start'th character,
and extending for count characters if that is specified. (Same as
substring(string from start for count).)

substr ( bytes bytea, start integer [, count integer ] ) → bytea
Extracts the substring of bytes starting at the start'th byte, and
extending for count bytes if that is specified. (Same as
substring(bytes from start for count).)

new patch attached.
main changes:
1. change 3 argument func argument from
(string text, pattern text, escape_character text)
to
(string text, pattern text, escape text)

2. add synopsis section in 9.7.3. POSIX Regular Expressions for
function substring.
we only have the synopsis section for function substring in 9.7.2
section, now add it to 9.7.3.
also add an example about using named natation call substring:
substring(string=>'foobar', pattern=> 'o.b')

the patch is small, I just put the
\df substring
\df substr
(before and after patch) output into the commit message.