I'm probably missing something fundamentally simple here, but I can't work it out....

I'm trying to cache database results by putting the return of fetchrow_hashref into a hash, single thread works fine but when I share the cache hash I'm getting an "Invalid value for shared scalar" error...

Example of what I'm trying:

my (%aCache)    : shared;
my ($cacheHit)  : shared = 0;
my ($cacheMiss) : shared = 0;

sub Do_Stuff () {
    my ($Id,
        $aDate,
        $aValue) = @_;
    
    my ($dbh, $sth, $row);
    # Check if the required information is in the cache before doing a
+nything else.
    my ($cacheKey) = sprintf("%s:%s:%s", $Id, $aDate, $aValue);
    if (exists $aCache{$cacheKey}) {
        lock ($cacheHit);
        $cacheHit++;
        #
        #  Put cached data in $row
        #
        $row = $aCache{$cacheKey};
    } else
    {
        {
            lock ($cacheMiss);
            $cacheMiss++;
        }

        my $dbh = DBI->connect("Whatever DB",'Default', '')
            or die "Can't connect to Whatever DB database: $DBI::errst
+r\n";
    
        $sth = $dbh->prepare(
            "SELECT a, "
                 . "b, "
                 . "c "
           . "FROM mytable "
           . "WHERE a = ? ")
            or die "Couldn't prepare statement: $dbh->errstr";

    
        $sth->bind_param(1, $Id);
        $sth->execute();
        #
        # Store new row in the cache.
        #  This causes an "Invalid value for shared scalar error:
        $aCache{$cacheKey} = $sth->fetchrow_hashref();
        #
        #  Put the result in $row
        #
        $row = $aCache{$cacheKey};
        $sth->finish();
        $dbh->disconnect();
    }
}

[download]

In reply to threads::shared and DBI fetchrow_hashref by matonb

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.