Re: String Translation

On Thursday, October 16, 2003, at 11:01 AM, Dror Matalon wrote:

> 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.

Looking at it, I realized what the problem is. It's really dumb. Recall
that the code looked 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);
}
}

The upshot is that $table may have many rows with the same value in the
name column! For example, I have over 2200 rows in the table, but when
I do "SELECT DISTINCT name", there are only 24!! So it was getting all
2200 rows, and thinking it was changing them one at a time, but it was
actually changing them over and over again!

So my solution is just to add the DISTINCT.

Naturally, after doing this, the whole thing took only a second to run!

Sorry for sharing this blunder with you all and wasting all of our time!

Regards,

David

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