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Re: dbi_query_iterator and my misunderstanding the $row

by japhy (Canon)
on Mar 01, 2007 at 04:02 UTC ( #602643=note: print w/ replies, xml ) Need Help??


in reply to dbi_query_iterator and my misunderstanding the $row

I think this is because fetchrow_arrayref uses the same location in memory every time, as the DBI docs state: Note that the same array reference is returned for each fetch, so don't store the reference and then use it after a later fetch. Also, the elements of the array are also reused for each row, so take care if you want to take a reference to an element.


Jeff japhy Pinyan, P.L., P.M., P.O.D, X.S.: Perl, regex, and perl hacker
How can we ever be the sold short or the cheated, we who for every service have long ago been overpaid? ~~ Meister Eckhart


Comment on Re: dbi_query_iterator and my misunderstanding the $row
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Re^2: dbi_query_iterator and my misunderstanding the $row
by jfroebe (Vicar) on Mar 01, 2007 at 22:04 UTC
      Oh, sorry. Maybe I misunderstood. Does the code actually work, and you want to know why it works?

      $oldrow is the previous row. The function that builds the iterator stores the first row before it creates the iterator function:

      sub dbi_query_iterator { my ($sth, @params) = @_; $sth->execute(@params) or return; # get the first row of results NOW my $row = $sth->fetchrow_arrayref(); return Iterator { my $action = shift() || 'nextval'; if ($action eq 'exhausted?') { return ! defined $row; } elsif ($action eq 'nextval') { # save the current row of results my $oldrow = $row; # get the next row of results $row = $sth->fetchrow_arrayref; # return the previous row (before we advanced) return $oldrow->[0]; } } }

      Jeff japhy Pinyan, P.L., P.M., P.O.D, X.S.: Perl, regex, and perl hacker
      How can we ever be the sold short or the cheated, we who for every service have long ago been overpaid? ~~ Meister Eckhart

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