http://www.perlmonks.org?node_id=479084

Tatnall has asked for the wisdom of the Perl Monks concerning the following question:

Updated below: I've got over 1 million records to go through as I normalize tables, which means I need to use DBI's fetchall_arrayref $max_size to keep memory usage in check unless there is a better way.

In my loop, I'm getting this error: Can't coerce array into hash at line 44. and can't figure out why since the same code worked minus the while statement for $max_size.

# Assuming: # # Table1 # +-----+-----------+ # | id | Name | # +-----+-----------+ # | 1 | Bill | # +-----+-----------+ # | 2 | Bob | # +-----+-----------+ # | 3 | Mike | # +-----+-----------+ # # Table2 before # +-----+-----------+ # | id | Name | # +-----+-----------+ # | ? | Mike | # +-----+-----------+ # | ? | Bob | # +-----+-----------+ # | ? | Bill | # +-----+-----------+ # # Table2 after # +-----+-----------+ # | id | Name | # +-----+-----------+ # | ? | 3 | # +-----+-----------+ # | ? | 2 | # +-----+-----------+ # | ? | 1 | # +-----+-----------+
#!/usr/local/bin/perl -w # print "Content-type: text/html\n\n"; use lib "/home/champ1/public_html/cgi-bin"; use warnings; use CGI::Carp qw(fatalsToBrowser); use strict; use CGI qw/:cgi/; use Data::Dumper; use Common; use Validate; use HTML::Template; use HTML::FillInForm; $|=1; #------------------------- declare -------------------------- my $query = new CGI; my ($sth, $stmt, $template, $hdrflg, $fvalues); #$hdrflg = + is set when a header is first written my ($dbh, $keylock, $basehref) = dbconnect(); #f $stmt = "SELECT id, name FROM table1"; $sth = execute_it($dbh,$stmt); my $table1 = $sth->fetchall_arrayref({}); my $max_rows = 2; my ($i, $j); $stmt = "SELECT id, name FROM table2"; $sth = $dbh->prepare($stmt); $sth->execute(); while (my $table2 = $sth->fetchall_arrayref(undef, $max_rows)) { for $i ( 0 .. $#$table2 ) { for $j ( 0 .. $#$table1 ) { ###line 44### if ( $table2->[$i]{'name'} eq $table1->[$j]{'name'} ) { $stmt = ("UPDATE table2 SET name = ? WHERE id = '$ +table2->[$i]{'id'}'"); $sth = $dbh->prepare($stmt); $sth->execute ( $table1->[$j]{'id'}); } } } }; close_db(); exit();

I used the super search and found one node, which wasn't very helpful. http://www.perlmonks.com/index.pl?node_id=320547

Update:

Thanks to gmax here is the code I ended up using.

It's currently running through the rows. :)

$stmt = "SELECT id, name FROM table1"; $sth = execute_it($dbh,$stmt); my $table1 = $sth->fetchall_arrayref({}); my ($i, $j, $sth2); $stmt = "SELECT id, name FROM table2"; $sth = $dbh->prepare($stmt); $sth->execute(); print "Content-type: text/plain \n\n"; my $max_rows = 500; my $rows = []; # cache for batches of rows while ( my $row = ( shift( @$rows ) || shift( @{$rows=$sth->fe +tchall_arrayref({},$max_rows) || []} ) ) ) { for ( $row ) { for $j ( 0 .. $#$table1 ) { if ( $row->{'name'} eq $table1->[$j]{'name'} ) { $stmt = qq/UPDATE table2 SET name = ? WHERE id = " +$row->{id}"/; print "Here.$j".Dumper ($stmt)."\n"; $sth2 = $dbh->prepare($stmt); $sth2->execute ( $table1->[$j]{'id'}); } } } }; close_db(); exit();

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