regexp_replace grief

[Armin Resch]

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

-ar

[Craig James]

Post by Armin Resch
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

Post by Armin Resch
-ar

[Armin Resch]

Thx for clarification, Craig. Your Perl snippet comes in handy, too.
-ar

Post by Armin Resch
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.
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

Post by Armin Resch
-ar