Re: String Translation

Hey David,

I would try the standard tuning things:

1. Run VACUUM ANALYZE on the table.
2. Run reindex on the table
2. Print out the query and then do a explain analyze of the query in
psql and see how long it takes, and if so why.

If it's still slow, provide the explain analyze here, and we can take a
look at it.

Dror

On Wed, Oct 15, 2003 at 05:21:14PM -0700, David Wheeler wrote:
> Hi All,
>
> I have an upgrade script for the forthcoming version of Bricolage. It
> has a function that looks like this:
>
> sub update_all {
> my ($table) = @_;
> my $get_name = prepare("SELECT name FROM $table");
> my $set_key_name = prepare("UPDATE $table SET key_name=? WHERE
> name=?");
>
> my $name;
> execute($get_name);
> bind_columns($get_name, \$name);
>
> while (fetch($get_name)) {
> my $key_name = lc($name);
> $key_name =~ y/a-z0-9/_/cs;
> execute($set_key_name, $key_name, $name);
> }
> }
>
> Now, this is all well and good, except that it takes _forever_ to run!
> I have it running now on a database with two tables to be updated, with
> a total of 2213 rows, and it has been running for about 30 mins. And
> yes, it's a fast server with a reasonably tuned database.
>
> Now, I could speed this up if it could just run in a single query,
> rather than with a big select and 2213 UPDATEs. The trouble is, I don't
> know of an SQL equivalent to y/a-z0-9/_/cs, which translates any non
> alphanumeric characters to underscores. I see that there's a
> substring() function that supports POSIX regular expressions, but that
> doesn't do a substitution.
>
> So my question is, does anyone know of a way I could do this in the
> database (and it is a one-time change [I hope!])? And if there is one,
> will it be faster?
>
> Many TIA,
>
> David
>
> --
> David Wheeler AIM: dwTheory
> david(at)kineticode(dot)com ICQ: 15726394
> http://www.kineticode.com/ Yahoo!: dew7e
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>

--
Dror Matalon
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