$ perl ./tux.pl #  
PostgreSQL 9.4devel_HEAD_20140502_2044_0717748 on x86_64-unknown-linux-gnu, compiled by gcc (GCC) 4.9.0, 64-bit

              prepare  execute  finish
 no where     0.00007  5.52991  0.02707
 no where     0.00005  5.42172  0.03283
 no where     0.00005  5.42320  0.03247

where 0=1     0.00005  0.00049  0.00000
where 0=1     0.00002  0.00013  0.00000
where 0=1     0.00002  0.00012  0.00000


##</code><code>##

use strict;
use warnings;
use DBI;
use Time::HiRes qw/gettimeofday tv_interval/;
my $dbh = DBI->connect or die "oops - $!\n";
print $dbh->selectrow_arrayref('select version()')->[0], "\n\n";
my $sql1 = "select * from foo";
my $sql2 = "select * from foo where 0 = 1";
print "              prepare  execute  finish\n";
time_this( $dbh, $sql1, ' no where' );
time_this( $dbh, $sql1, ' no where' );
time_this( $dbh, $sql1, ' no where' );
print "\n";
time_this( $dbh, $sql2, 'where 0=1');
time_this( $dbh, $sql2, 'where 0=1' );
time_this( $dbh, $sql2, 'where 0=1' );

sub time_this {
	my ($dbh, $sql, $how) = @_;
	my $t0;
	$t0 = [gettimeofday];
	my $sth = $dbh->prepare( $sql );
	print $how, "   ";
	printf("  %7.5f", tv_interval($t0 , [gettimeofday]));
	$t0 = [gettimeofday];
	$sth->execute;
	printf("  %7.5f", tv_interval($t0 , [gettimeofday]));
	my @fld = @{$sth->{NAME}};
	$t0 = [gettimeofday];
	$sth->finish;
	printf("  %7.5f", tv_interval($t0 , [gettimeofday]));
	print "\n";
}