Re: regexp_replace grief

On Wed, Apr 10, 2013 at 4:59 PM, Armin Resch <reschab(at)gmail(dot)com> wrote:

> Not sure this is the right list to vent about this but here you go:
>
> I) select regexp_replace('BEFORE.AFTER','(.*)\..*','\1','g') "Substring"
> II) select regexp_replace('BEFORE.AFTER','(.*)\\..*','\\1','g') "Substring"
>
> Executing (II) against pg 8.4.4 or 9.0.4 yields 'BEFORE', but in order for
> 9.1.7 to yield the same one has to execute (I) .. bummer
>

This has nothing to do with regexp's. It's a change in how '\' is
interpreted in any quoted string. The change came with Postgres 9.x and is
documented in the release notes. It brings Postgres into compliance with
the SQL standard.

In Perl, I do something like this:

my $pg_bs_char;
if ($dbh->get_info($GetInfoType{SQL_DBMS_VER}) gt "09.00.00") {
$pg_bs_char = "\\"; # a single '\' for PG 9.1 and higher
} else {
$pg_bs_char = "\\\\"; # a double '\\' for PG up to 9.0
}

You can also revert to the old 8.x interpretation; see

http://www.postgresql.org/docs/9.1/static/runtime-config-compatible.html

Craig

>
> -ar
>