I am trying to learn memcached, so I installed it on my laptop and fired it up. I also created a simple SQLite db 'mem.sqlite' like so 

CREATE TABLE t (id INTEGER PRIMARY KEY, str TEXT)

[download]

and filled the table with 20_000 random strings. Then I used the following simplistic script to benchmark. 

use Cache::Memcached;
my $memd = new Cache::Memcached {'servers' => [ "localhost:11212" ]};

use DBI qw(:sql_types);
my $dbh = DBI->connect("dbi:SQLite:dbname=mem.sqlite");

use Benchmark qw(:all);
my $count = 40_000;

cmpthese($count, {
    'query_dbh' =>     sub {
        my $id = int(rand(20_000));
        my $sth = $dbh->prepare("SELECT str FROM t WHERE id = ?");
        $sth->execute($id);
        my ($str) = $sth->fetchrow_array;
        
        open F, ">", "foo.txt" or die $!;
        print F "id: $id, str: $str\n";
        close F;
    },
    'query_mem' =>     sub {
        my $id = int(rand(20_000));
    
        open F, ">", "foo.txt" or die $!;
        my $str = $memd->get($id);
        unless ($str) {
            my $sth = $dbh->prepare("SELECT str FROM t WHERE id = ?");
            $sth->execute($id);
            ($str) = $sth->fetchrow_array;
            
            $memd->set($id, $str);
        }
        print F "id: $id, str: $str\n";
        close F;
    }
});

            Rate query_mem query_dbf
query_mem 2723/s        --      -29%
query_dbh 3846/s       41%        --

[download]

I consistently get results such as above, while I expected the memcache to slowly fill up and speed up the queries way faster than only accessing the file based db. What am I doing wrong, or are my expectations wrong?



when small people start casting long shadows, it is time to go to bed

In reply to learning memcached by punkish

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.