> push(@results,%$hash_ref);
I do not think this does what you think it does.
It will push an array of values (key1, value1, key2, value2, ...)
onto the @results array.
And I don't think pushing onto the @results array was the problem,
it was just the allRecords array you needed to worry about.
BTW, are all of the sql statements returning rows? If one or more
does not, then you would be pushing an undefined value like the
warning message says. And is it an error, or just a warning?
-----Original Message-----
From: STAFF [mailto:[EMAIL PROTECTED]]
Sent: Friday, May 25, 2001 10:02 AM
To: Mr. Sunray; [EMAIL PROTECTED]
Subject: Re: DBI, fork and IPC-Shareable - having problems
Indeed, you are passing references ..Shouldn't your dereference when you
push
onto @results like this:
$sth=$dbh->prepare($query);
$sth->execute();
while(my $hash_ref=$sth->fetchrow_hashref()){
push(@results,%$hash_ref);
}
Thus making an array of hashes instead of an array of hash_references?
It apparently sometimes works because your child get's to the reference
before
the Automatic garbage collection does and I don't think you can reference a
non-shared memory object from within a shared memory object which is what
you
would be doing by passing references instead of actual results.
(Correct me if I'm wrong on this, I'm not an expert on FORKing or Shared
memory, but I have learned quite a bit about Referencing and dereferencing
data
this last week, in the Perl Developer's Guide by Ed Peschko & Michele
DeWolfe,
Osborne publishing.)
On Fri, 25 May 2001 08:37:37 -0500, Mr. Sunray said:
> Hi all,
>
> Perl 5.6 on bughat 6.2, using DBI 1.14, DBD-Oracle 1.06.
>
> Ok - I thought I'd try and optimize a series of sql SELECT statements by
>
> forking each one and storing the results in a shared memory object.
>
> Here's the code - I'm reading a series of sql select statements from a
> file, fork'ing a child for each one, executing the 'fetch' within the
> child and trying to store the results in an array for later retrieval.
>
> The problem seems to be with the shared memory objects. Either the
> array of results grows each time I run the program or else I get "Can't
> use an undefined value as an ARRAY reference at
> /usr/local/lib/perl5/site_perl/5.6.0/IPC/Shareable.pm line 446, <GEN1>
> chunk whatever".
>
> Now, I've been told that part of the problem (at least) is that I'm
> trying
> to store references, which probably won't work (though it seems to
> work sometimes).
>
> I guess my big question is how can I use fork to speed up my queries
> *and*
> store the results in the parent (without using a text file)? Should I
> be
> looking at threads instead? Is there a *standard idiom*?
>
> Thanks in advance for any help.
>
> WARNING - be prepared to use 'ipcs' and 'ipcrm' if you want to play with
>
> this script! You may have stray memory objects floating around
> afterwards.
>
> Be sure to run this/your program at least twice to make sure your shared
>
> memory objects aren't "collecting".
>
> #!/usr/local/bin/perl -w
>
> use strict;
> use DBI;
> use DBD::Oracle;
> use IPC::Shareable;
> use IO::File;
> use POSIX qw(WNOHANG);
>
> use constant DB => 'myDB';
> use constant USER => 'user';
> use constant PASSWD => 'passwd';
> use constant DRIVER => 'Oracle';
>
> #+++++++++++++++++++++++++++++++++++++++++++++
> # File contains 4 sql SELECT statements.
> # Use "select sysdate from dual" if you like, so long as it works.
> #+++++++++++++++++++++++++++++++++++++++++++++
> use constant SQLFILE => 'file.sql';
>
> # Child handler
> $SIG{CHLD} = \&reapChild;
>
> my($dbh, $sth, @results, @allRecords);
> my $if = IO::File->new(SQLFILE) or die "Couldn't open file: $!\n";
>
> #+++++++++++++++++++++++++++++++++++++++++++++++++
> # I am not entirely sure what the proper settings for these should be.
> # I've tried various combinations with no (or bad) luck.
> #+++++++++++++++++++++++++++++++++++++++++++++++++
> my $glue = 'data';
> my %options = (create => 'yes', exclusive => 0, destroy=>1)
> tie @allRecords, 'IPC::Shareable', $glue, { %options } or die "Tie
> failed: $!\n";
>
> $/ = ""; # We're going to read each 'select' statement as an input
> record
> while(my $query = <$if>){
> chomp($query);
>
> my $child = fork();
> die "Can't fork: $!\n" unless defined $child;
>
> if($child == 0){
>
> # Not sure if I need 'InactiveDestroy' here or not
> $dbh = DBI->connect(DB,USER,PASSWD,DRIVER,
> {RaiseError=>1,PrintError=>1,InactiveDestroy=>1}
> );
>
> $sth = $dbh->prepare($query);
> $sth->execute();
> while( my $hash_ref = $sth->fetchrow_hashref() ){
> push(@results, $hash_ref);
> }
>
> #+++++++++++++++++++++++++++++++++++++++++++++
> # '@allRecords' should contain a reference to an array of hash
> # reference for each select statement (thus, four total).
> #+++++++++++++++++++++++++++++++++++++++++++++
> push(@allRecords, \@results);
>
> $sth->finish();
> $dbh->disconnect();
> exit 0;
> }
> }
>
> close($if) or die "Unable to close input file: $!\n";
>
> #+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> # I expect to see four array references here. When I try this, I either
>
> # get "Can't use undefined value as an array reference" warnings
> # from the 'Shareable.pm' module or the list keeps growing and growing
> # each time I run the program. What do I need to do?
> #+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> foreach my $ref(@allRecords){
> print "Ref is: $ref\n";
> }
>
> sub reapChild{ do {} while waitpid(-1, WNOHANG) > 0 }
>
>
>
>
>
>
--
Michael Wray
Network Administrator
FamilyConnect, Inc.
