On 06/12/10 16:12, Jonathan Leffler wrote:
>
> On Mon, Dec 6, 2010 at 07:20, Tim Bunce <tim.bu...@pobox.com
> <mailto:tim.bu...@pobox.com>> wrote:
>
> On Mon, Dec 06, 2010 at 12:54:57AM -0800, Jonathan Leffler wrote:
> > Two related questions (prompted by a question from people using
> > DBD::Informix):
> >
> > 1. Are there any known problems with $sth->fetchall_arrayref({}, 50);?
>
> Nope.
>
>
> OK - thanks for the quick look, Tim (and Martin). That quickly isolates the
> problem to DBD::Informix.
>
>
> > 2. Are there any requirements on a DBD module to make the limit on
> > fetchall_arrayref({}, 50) notation work, or is it purely a DBI feature?
>
> The DBI provides a default fetchall_arrayref method in DBI.pm that
> implements fetching, slicing and maxrows.
>
> There's also a fetchall_arrayref method in Driver.xst for added speed.
> That one falls-back to the perl version if a slice is specified, but
> otherwise expects dbdxst_fetchall_arrayref() to handle maxrows.
> dbdxst_fetchall_arrayref() is defined in Driver_xst.h
>
>
> AFAIK, I'm using the DBI-provided fetchall; the only reference to fetchall in
> Informix.pm is in POD. It appears in Informix.xsi and Informix.c, but that
> is stuff from DBI and the driver support code.
>
> I've attached the output of:
>
> DBI_TRACE=9 perl fetchall_maxrows_bug.pl <http://fetchall_maxrows_bug.pl>
>
> The fetchall_arrayref call was:
>
> fetchall_arrayref(undef, 50);
>
> I'm not sure how many problems that is revealing. The most immediately
> relevant section looks like:
>
> >> execute DISPATCH (DBI::st=HASH(0x1009177a8) rc1/1 @1 g2 ima1041
> pid#74162) at fetchall_maxrows_bug.pl <http://fetchall_maxrows_bug.pl> line 8
> -> execute for DBD::Informix::st (DBI::st=HASH(0x1009177a8)~0x1009176d0)
> -->> DBD::Informix::dbd_ix_st_execute()
> -->> DBD::Informix::dbd_ix_open()
> <<-- DBD::Informix::dbd_ix_open()
> <<-- DBD::Informix::dbd_ix_st_execute()
> <- execute= ( '0E0' ) [1 items] at fetchall_maxrows_bug.pl
> <http://fetchall_maxrows_bug.pl> line 8
> >> fetchall_arrayref DISPATCH (DBI::st=HASH(0x1009177a8) rc1/1 @3 g2 ima1
> pid#74162) at fetchall_maxrows_bug.pl <http://fetchall_maxrows_bug.pl> line 16
> -> fetchall_arrayref for DBD::Informix::st
> (DBI::st=HASH(0x1009177a8)~0x1009176d0 undef 50)
dbd_st_fetch should get called here via $sth->fetch.
The code in DBI seems fairly straight forward:
sub fetchall_arrayref { # ALSO IN Driver.xst
my ($sth, $slice, $max_rows) = @_;
# when batch fetching with $max_rows were very likely to try to
# fetch the 'next batch' after the previous batch returned
# <=$max_rows. So don't treat that as an error.
return undef if $max_rows and not $sth->FETCH('Active');
my $mode = ref($slice) || 'ARRAY';
my @rows;
my $row;
if ($mode eq 'ARRAY') {
# we copy the array here because fetch (currently) always
# returns the same array ref. XXX
if ($slice && @$slice) {
$max_rows = -1 unless defined $max_rows;
push @rows, [ @{$row}[ @$slice] ]
while($max_rows-- and $row = $sth->fetch);
}
elsif (defined $max_rows) {
push @rows, [ @$row ]
while($max_rows-- and $row = $sth->fetch); <---- why didn't
you get here?
}
else {
push @rows, [ @$row ] while($row = $sth->fetch);
}
}
Is your $sth Active?
> <- fetchall_arrayref= ( undef ) [1 items] row-1 at
> fetchall_maxrows_bug.pl <http://fetchall_maxrows_bug.pl> line 16
> >> disconnect DISPATCH (DBI::db=HASH(0x1009175c8) rc1/1 @1 g2 ima10c01
> pid#74162) at fetchall_maxrows_bug.pl <http://fetchall_maxrows_bug.pl> line 30
> -> disconnect for DBD::Informix::db
> (DBI::db=HASH(0x1009175c8)~0x1009174c0)
>
> It seems that the DISPATCH code is doing something, but not reaching
> DBD::Informix code (the DBD::Informix debugging usually has the double-headed
> arrows (-->> or <<--) but it doesn't show any activity.
>
> By contrast, when I used the variant with just a slice
> (fetchall_arrayref([0,1,2])), I get to see:
>
> <- execute= ( '0E0' ) [1 items] at fetchall_maxrows_bug.pl
> <http://fetchall_maxrows_bug.pl> line 8
> >> fetchall_arrayref DISPATCH (DBI::st=HASH(0x1009177d8) rc1/1 @2 g2 ima1
> pid#74507) at fetchall_maxrows_bug.pl <http://fetchall_maxrows_bug.pl> line 12
> -> fetchall_arrayref for DBD::Informix::st
> (DBI::st=HASH(0x1009177d8)~0x100917700 ARRAY(0x1009174a8))
> >> fetch DISPATCH (DBI::st=HASH(0x100917700) rc1/2 @1 g2 ima0
> pid#74507) at
> /Users/jleffler/perl/v5.13.4/lib/site_perl/5.13.4/darwin-2level/DBI.pm line
> 2016 via at fetchall_maxrows_bug.pl <http://fetchall_maxrows_bug.pl> line 12
> 1 -> fetch for DBD::Informix::st (DBI::st=HASH(0x100917700)~INNER)
> -->> DBD::Informix::dbd_ix_st_fetch()
> -->> DBD::Informix::dbd_ix_blobs()
> ---- dbd_ix_blobs(): 0 BYTE/TEXT blobs
> <<-- DBD::Informix::dbd_ix_blobs()
> ---- dbd_ix_st_fetch: FETCH c_000000000 into d_000000000
> dbih_setup_fbav alloc for 7 fields
> dbih_setup_fbav now 7 fields
> ---- dbd_ix_st_fetch colno 1: coltype = 2
> ---- dbd_ix_st_fetch colno 2: coltype = 0
> ---- dbd_ix_st_fetch colno 3: coltype = 0
> ---- dbd_ix_st_fetch colno 4: coltype = 5
> ---- dbd_ix_st_fetch colno 5: coltype = 1
> ---- dbd_ix_st_fetch colno 6: coltype = 0
> ---- dbd_ix_st_fetch colno 7: coltype = 0
> <<-- DBD::Informix::dbd_ix_st_fetch()
> 1 <- fetch= ( [ '1' 'H ' 'Hydrogen ' '1.0079' '1' '1 ' 'Y' ] )
> [1 items] row1 at
> /Users/jleffler/perl/v5.13.4/lib/site_perl/5.13.4/darwin-2level/DBI.pm line
> 2016 via at fetchall_maxrows_bug.pl <http://fetchall_maxrows_bug.pl> line 12
>
> Can you see anything to indicate what I've got mis-initialized that is
> causing the breakage, Tim (or anyone)? Superficially, it looks like DBI
> decided not to call the DBD::Informix fetch functions when maxrows was in
> effect. There must be a reason, but I've no idea what to look for.
Also double-check you rebuilt DBD::Informix after installing DBI 1.615 -
although I think DBI catches that now.
>
> p.s. I took a quick look at DBD::Informix source and ran away fast! :)
>
>
> Fair enough...it probably needs a complete rewrite.
>
> I had been going to release a new DBD::Informix with support for Perl 5.13 /
> 5.14. I probably need to hold off until I've resolved this problem.
>
> Strictly, I'm using DBD::Informix version 2010.0914.20100929; however, it is
> essentially the same as DBD::Informix 2008.0513 - especially in this area.
>
>
> > my $dbh = DBI->connect('dbi:Informix:stores', '', '') or die "Horribly
> 1";
> > my $sth = $dbh->prepare(q{SELECT * FROM Elements}) or die "Horribly 2";
> > $sth->execute;
> >
> > #my $res = $sth->fetchall_arrayref; # Works
> > #my $res = $sth->fetchall_arrayref({}, 50); # Fails: no data
> > #my $res = $sth->fetchall_arrayref([], 50); # Fails: no data
> > #my $res = $sth->fetchall_arrayref([0,1,2]); # Works
> > my $res = $sth->fetchall_arrayref([0,1,2], 50); # Fails: no data
> > #my $res = $sth->fetchall_arrayref({}); # Works
> > #my $res = $sth->fetchall_arrayref(undef, 50); # Fails: no data
> > foreach my $row (@{$res})
> > {
> > # Use this section for printing arrays
> > foreach my $value (@{$row})
> > {
> > printf "%s ", $value;
> > }
> > print "\n";
> > # Use this section for printing hashes
> > #foreach my $key (sort keys %{$row})
> > #{
> > # printf "%-15s = %s\n", $key, $row->{$key};
> > #}
> > }
> >
> > $dbh->disconnect;
> >
> > Choose your own driver and database, etc; choose your own table (my
> table of
> > elements has entries for hydrogen through ununoctium - 1..118; 50 is
> about
> > half the table). It seems that fetchall_arrayref() works fine with no
> > arguments and with slice arguments, but none of the slice versions with
> a
> > maximum count does anything.
> >
> > Am I missing something? Or is there a bug?
> >
> > Perl 5.13.4 on MacOS X 10.6.5; DBI 1.615, DBD::Informix 2008.0513.
>
>
>
> --
> Jonathan Leffler <jonathan.leff...@gmail.com
> <mailto:jonathan.leff...@gmail.com>> #include <disclaimer.h>
> Guardian of DBD::Informix - v2008.0513 - http://dbi.perl.org
> "Blessed are we who can laugh at ourselves, for we shall never cease to be
> amused."
Martin
--
Martin J. Evans
Easysoft Limited
http://www.easysoft.com
