On Mon, Dec 6, 2010 at 07:20, Tim Bunce <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
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 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 line 8
>> fetchall_arrayref DISPATCH (DBI::st=HASH(0x1009177a8) rc1/1 @3 g2
ima1 pid#74162) at fetchall_maxrows_bug.pl line 16
-> fetchall_arrayref for DBD::Informix::st
(DBI::st=HASH(0x1009177a8)~0x1009176d0 undef 50)
<- fetchall_arrayref= ( undef ) [1 items] row-1 at
fetchall_maxrows_bug.pl line 16
>> disconnect DISPATCH (DBI::db=HASH(0x1009175c8) rc1/1 @1 g2 ima10c01
pid#74162) at 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 line 8
>> fetchall_arrayref DISPATCH (DBI::st=HASH(0x1009177d8) rc1/1 @2 g2
ima1 pid#74507) at 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 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 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.
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> #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."
dbi.trace.9
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