Fixed column_info's return value order.

DBI.pm's pod says
> The result set is ordered by TABLE_CAT, TABLE_SCHEM, TABLE_NAME and
> ORDINAL_POSITION.

ref. https://github.com/CaptTofu/DBD-mysql/issues/16

lib/DBD/mysql.pm

@@ -452,6 +452,7 @@ sub column_info {
   }
 
   my $ordinal_pos = 0;
+  my @fields;
   for my $row (@$desc)
   {
     my $type = $row->{type};
@@ -460,6 +461,7 @@ sub column_info {
     my $typemod   = $2;
     my $attr      = $3;
 
+    push @fields, $row->{field};
     my $info = $col_info{ $row->{field} }= {
 	    TABLE_CAT               => $catalog,
 	    TABLE_SCHEM             => $schema,
@@ -583,7 +585,7 @@ sub column_info {
           return $dbh->DBI::set_err($DBI::err, "DBI::Sponge: $DBI::errstr"));
 
   my $sth = $sponge->prepare("column_info $table", {
-      rows          => [ map { [ @{$_}{@names} ] } values %col_info ],
+      rows          => [ map { [ @{$_}{@names} ] } map { $col_info{$_} } @fields ],
       NUM_OF_FIELDS => scalar @names,
       NAME          => \@names,
       }) or

t/40catalog.t

@@ -22,7 +22,7 @@ eval {$dbh= DBI->connect($test_dsn, $test_user, $test_password,
 if ($@) {
     plan skip_all => "ERROR: $DBI::errstr. Can't continue test";
 }
-plan tests => 77;
+plan tests => 78;
 
 ok(defined $dbh, "connecting");
 
@@ -281,6 +281,13 @@ SKIP: {
   ($info)= $sth->fetchall_arrayref({});
   is(scalar @$info, 1);
 
+  #
+  # The result set is ordered by TABLE_CAT, TABLE_SCHEM, TABLE_NAME and ORDINAL_POSITION.
+  #
+  $sth= $dbh->column_info(undef, undef, "t1", undef);
+  my ($info)= $sth->fetchall_arrayref({});
+  is(join(' ++ ', map { $_->{COLUMN_NAME} } @{$info}), "a ++ b ++ a_ ++ a'b ++ bar");
+
   ok($dbh->do(qq{DROP TABLE IF EXISTS t1}), "cleaning up");
   $dbh->disconnect();
 };