Обсуждение: Perl error: fetchrow_hashref failed

Hi, I wonder if I might tap the vast knowledge here againg.

I have a perl script that is looping through a statement handle like this.

$statement = "select * from sometable";
$sth=$dbh->prepare($statement);
$sth->execute();

# here is the part I have a question about.
while (%hash_ref = %{$sth->fetchrow_hashref}) {

    while (($k,$v) = each (%hash_ref)) {
        print ("\n$k == $v"); }
}

The problem is that when I have exhausted the statement handle in the first
while statement I get this error.

DBD::Pg::st fetchrow_array failed: no statement executing

It's not fatal, but it is filling my error log. Is there a way I can suppers
this?

Does it hurt anything for me to be loop through the statement like this?


Thanks in advance
Jeff Seese

----- Original Message -----
From: "Jeffrey" <seesej@uswest.net>
To: <pgsql-general@postgresql.org>
Sent: Wednesday, April 12, 2000 10:05 AM
Subject: [GENERAL] Perl error: fetchrow_hashref failed


> Hi, I wonder if I might tap the vast knowledge here againg.
>
> I have a perl script that is looping through a statement handle like this.
>
> $statement = "select * from sometable";
> $sth=$dbh->prepare($statement);
> $sth->execute();
>
> # here is the part I have a question about.
> while (%hash_ref = %{$sth->fetchrow_hashref}) {
>
>     while (($k,$v) = each (%hash_ref)) {
>         print ("\n$k == $v"); }
> }

I don't think your first loop will work because the %{$b} where $b is undef
will not produce an undef - I think.

See if this works? It ought to be more efficient anyway, because you only
need one hash in my version, not two like your routine (that created by the
fetchrow_hashref call and the hash %hashref itself.

while (defined $hash_ref=$sth->fetchrow_hashref) {
    while (($k,$v)=each %$hashref) {
        print ("\n$k==$v");
    }
}

Your script works fine, but I still get the same error.

I can duplicate this same error with a non-hash ref like this.

$sth=$dbh->prepare("select param1,param2 from sometable");
$sth->execute;

while (($param1,$param2) = $sth->fetchrow_array) {
    ...... do something with them .
  }

My concern is, does the error fetchrow_hashref or _array cause any problems
with the server, postmaster, postgres, etc. I am about to turn a site on
with lots of traffic and I don't want to crash because of these errors.

Thank you
js

> From: "Moray McConnachie" <moray.mcconnachie@computing-services.oxford.ac.uk>
> Date: Wed, 12 Apr 2000 12:45:42 +0100
> To: "Jeffrey" <seesej@uswest.net>, " " <pgsql-general@postgresql.org>
> Subject: Re: [GENERAL] Perl error: fetchrow_hashref failed
>
>
> ----- Original Message -----
> From: "Jeffrey" <seesej@uswest.net>
> To: <pgsql-general@postgresql.org>
> Sent: Wednesday, April 12, 2000 10:05 AM
> Subject: [GENERAL] Perl error: fetchrow_hashref failed
>
>
>> Hi, I wonder if I might tap the vast knowledge here againg.
>>
>> I have a perl script that is looping through a statement handle like this.
>>
>> $statement = "select * from sometable";
>> $sth=$dbh->prepare($statement);
>> $sth->execute();
>>
>> # here is the part I have a question about.
>> while (%hash_ref = %{$sth->fetchrow_hashref}) {
>>
>> while (($k,$v) = each (%hash_ref)) {
>> print ("\n$k == $v"); }
>> }
>
> I don't think your first loop will work because the %{$b} where $b is undef
> will not produce an undef - I think.
>
> See if this works? It ought to be more efficient anyway, because you only
> need one hash in my version, not two like your routine (that created by the
> fetchrow_hashref call and the hash %hashref itself.
>
> while (defined $hash_ref=$sth->fetchrow_hashref) {
> while (($k,$v)=each %$hashref) {
> print ("\n$k==$v");
> }
> }
>
>
>
>

All I can say is I get no errors of this kind in my code, which runs

 $sth=$dbh->prepare("select param1,param2 from sometable");
 $sth->execute;

 while (@resultset = $sth->fetchrow_array) {
     ...... do something with them .
   }
$sth->finish;


I don't think calling $sth-finish should make the difference, but maybe if
you have already used $sth once there is a problem?
Try it anyway :->
----------------------------------------------------------------
Moray.McConnachie@computing-services.oxford.ac.uk
----- Original Message -----
From: "Jeffrey" <seesej@uswest.net>
To: "Moray McConnachie" <moray.mcconnachie@computing-services.oxford.ac.uk>;
<pgsql-general@postgresql.org>
Sent: Wednesday, April 12, 2000 12:57 PM
Subject: Re: [GENERAL] Perl error: fetchrow_hashref failed


> Your script works fine, but I still get the same error.
>
> I can duplicate this same error with a non-hash ref like this.
>
> $sth=$dbh->prepare("select param1,param2 from sometable");
> $sth->execute;
>
> while (($param1,$param2) = $sth->fetchrow_array) {
>     ...... do something with them .
>   }
>
> My concern is, does the error fetchrow_hashref or _array cause any
problems
> with the server, postmaster, postgres, etc. I am about to turn a site on
> with lots of traffic and I don't want to crash because of these errors.
>
> Thank you
> js
>
> > From: "Moray McConnachie"
<moray.mcconnachie@computing-services.oxford.ac.uk>
> > Date: Wed, 12 Apr 2000 12:45:42 +0100
> > To: "Jeffrey" <seesej@uswest.net>, " " <pgsql-general@postgresql.org>
> > Subject: Re: [GENERAL] Perl error: fetchrow_hashref failed
> >
> >
> > ----- Original Message -----
> > From: "Jeffrey" <seesej@uswest.net>
> > To: <pgsql-general@postgresql.org>
> > Sent: Wednesday, April 12, 2000 10:05 AM
> > Subject: [GENERAL] Perl error: fetchrow_hashref failed
> >
> >
> >> Hi, I wonder if I might tap the vast knowledge here againg.
> >>
> >> I have a perl script that is looping through a statement handle like th
is.
> >>
> >> $statement = "select * from sometable";
> >> $sth=$dbh->prepare($statement);
> >> $sth->execute();
> >>
> >> # here is the part I have a question about.
> >> while (%hash_ref = %{$sth->fetchrow_hashref}) {
> >>
> >> while (($k,$v) = each (%hash_ref)) {
> >> print ("\n$k == $v"); }
> >> }
> >
> > I don't think your first loop will work because the %{$b} where $b is
undef
> > will not produce an undef - I think.
> >
> > See if this works? It ought to be more efficient anyway, because you
only
> > need one hash in my version, not two like your routine (that created by
the
> > fetchrow_hashref call and the hash %hashref itself.
> >
> > while (defined $hash_ref=$sth->fetchrow_hashref) {
> > while (($k,$v)=each %$hashref) {
> > print ("\n$k==$v");
> > }
> > }
> >
> >
> >
> >
>
>
>

I think the cleanest way to handle this is:

while ($Rhash = $sth->fetchrow_hashref) {
  do something with %$Rhash or just refer to $Rhash->{fieldname}
}

The array-based version below, if I remember correctly, can fail in
certain cases, including if both params are undefined.  The code above
succeeds because the assignment is always either a hashref or undefined,
never an array partially consisting of undefined values.

BTW, the DBI docs suggest that the *fastest* way to do it is with
$sth->fetchrow_arrayref.

Cheers,
Andy Perrin

> All I can say is I get no errors of this kind in my code, which runs
>
>  $sth=$dbh->prepare("select param1,param2 from sometable");
>  $sth->execute;
>
>  while (@resultset = $sth->fetchrow_array) {
>      ...... do something with them .
>    }
> $sth->finish;
>
>
> I don't think calling $sth-finish should make the difference, but maybe if
> you have already used $sth once there is a problem?
> Try it anyway :->
> ----------------------------------------------------------------
> Moray.McConnachie@computing-services.oxford.ac.uk
> ----- Original Message -----
> From: "Jeffrey" <seesej@uswest.net>
> To: "Moray McConnachie" <moray.mcconnachie@computing-services.oxford.ac.uk>;
> <pgsql-general@postgresql.org>
> Sent: Wednesday, April 12, 2000 12:57 PM
> Subject: Re: [GENERAL] Perl error: fetchrow_hashref failed
>
>
> > Your script works fine, but I still get the same error.
> >
> > I can duplicate this same error with a non-hash ref like this.
> >
> > $sth=$dbh->prepare("select param1,param2 from sometable");
> > $sth->execute;
> >
> > while (($param1,$param2) = $sth->fetchrow_array) {
> >     ...... do something with them .
> >   }
> >
> > My concern is, does the error fetchrow_hashref or _array cause any
> problems
> > with the server, postmaster, postgres, etc. I am about to turn a site on
> > with lots of traffic and I don't want to crash because of these errors.
> >
> > Thank you
> > js
> >
> > > From: "Moray McConnachie"
> <moray.mcconnachie@computing-services.oxford.ac.uk>
> > > Date: Wed, 12 Apr 2000 12:45:42 +0100
> > > To: "Jeffrey" <seesej@uswest.net>, " " <pgsql-general@postgresql.org>
> > > Subject: Re: [GENERAL] Perl error: fetchrow_hashref failed
> > >
> > >
> > > ----- Original Message -----
> > > From: "Jeffrey" <seesej@uswest.net>
> > > To: <pgsql-general@postgresql.org>
> > > Sent: Wednesday, April 12, 2000 10:05 AM
> > > Subject: [GENERAL] Perl error: fetchrow_hashref failed
> > >
> > >
> > >> Hi, I wonder if I might tap the vast knowledge here againg.
> > >>
> > >> I have a perl script that is looping through a statement handle like th
> is.
> > >>
> > >> $statement = "select * from sometable";
> > >> $sth=$dbh->prepare($statement);
> > >> $sth->execute();
> > >>
> > >> # here is the part I have a question about.
> > >> while (%hash_ref = %{$sth->fetchrow_hashref}) {
> > >>
> > >> while (($k,$v) = each (%hash_ref)) {
> > >> print ("\n$k == $v"); }
> > >> }
> > >
> > > I don't think your first loop will work because the %{$b} where $b is
> undef
> > > will not produce an undef - I think.
> > >
> > > See if this works? It ought to be more efficient anyway, because you
> only
> > > need one hash in my version, not two like your routine (that created by
> the
> > > fetchrow_hashref call and the hash %hashref itself.
> > >
> > > while (defined $hash_ref=$sth->fetchrow_hashref) {
> > > while (($k,$v)=each %$hashref) {
> > > print ("\n$k==$v");
> > > }
> > > }
> > >
> > >
> > >
> > >
> >
> >
> >
>