MCE and DBI - [SOLVED]

[pmamatsis]

Hello everybody, i would like to seek some advice for the MCE parallel library.
I have an assignment at the office that i need to use it along with one database connection per worker process.
What i am doing is...i am creating a database connection into the "main" body of my perl script in order to construct an array and then i am passing this array into the 'worker' sub.
The problem rises when into the 'worker' sub i am trying to connect to the database again in order to execute a stored procedure based on the arguments provided by the main process...i am getting a series of errors about re-defining some functions from the DBI. One of the errors is the following:

Subroutine DBI::st::ora_stmt_type redefined at C:/Perl64/site/lib/DBI.
+pm line 1405, <__ANONIO__> line 2.

What am i missing about the use of the MCE library ? Any kind of advice of what i am doing wrong ?

Best regards and
thank you in advance,
Panos.

[marioroy]

Hi Panos,

Thank you for providing a code sample. I added user_begin and user_end options. In MCE, workers call user_begin and user_end one time (before and after running). Thus, reconnecting to the DB each time is not necessary.

e.g. { user_begin } { user_func chunk_1 } { user_func chunk_2 } ... { user_func chunk_N } { user_end }

#!/usr/bin/perl -w
use strict;

use MCE;
use DBD::Oracle;
use DBI;

sub myBegin {
    my ($mce) = @_;
    $mce->{db} = DBI->connect(
       "dbi:Oracle:<SERVER_NAME>", "<USERID>", "<PASSWORD>"
    ) || die($DBI::errstr . "\n");
    return;
}

sub myEnd {
    my ($mce) = @_;
    $mce->{db}->disconnect;
    return;
}

sub mySub {
    my ($mce, $chunk_ref, $chunk_id) = @_;
    my $db = $mce->{db};

    return;
}

my (@array, $mceObj, $db);

$db = DBI->connect(
   "dbi:Oracle:<SERVER_NAME>", "<USERID>", "<PASSWORD>"
) || die($DBI::errstr . "\n");

...do some work with the database in order to fill up
...the @array variable...

$db->disconnect;

$mceObj = MCE->new(max_workers => 4,
                   input_data => \@array,
                   user_begin => \&myBegin,
                   user_func => \&mySub,
                   user_end => \&myEnd);

$mceObj->run;

From reading your code, am still not sure the reason for the ora_stmt_type redefined errors stated in the initial post. Connecting one time may solve the issue.

[pmamatsis]

Hi @marioroy,
let me thank you once more for your quick reply and assistance.
I have tried your suggestion and it works like a charm! I am also not quite sure about the 'why' the perl runtime complaints about the DBI ora_stmt_type redefined errors but anyway...for the time being this solution is perfect !

Best regards,
Panos.

[marioroy]

That is great, especially no more DBI ora_stmt_type redefined errors.

[marioroy]

Without a code sample in question am not sure what to suggest other than MCE includes DBI examples (MCE-1.608/examples/sampledb/) which may be helpful.

[pmamatsis]

Hi @marioroy,
thank you so much for your quick reply. I am sorry for not posting any code online but i didn't want for people to think that i just need somebody else to resolve my problem. :)
The full source code for my little program is as following:



#!/usr/bin/perl -w

use strict;<br>

use MCE;
use DBD::Oracle;
use DBI;

sub mySub {
    my $db;
    $db=DBI->connect("dbi:Oracle:<SERVER_NAME>", "<USERID>", "<PASSWOR
+D>") || die($DBI::errstr . "\n");
    $db->disconnect;

    return;
}

my (@array, $mceObj, $db);

$db=DBI->connect("dbi:Oracle:<SERVER_NAME>", "<USERID>", "<PASSWORD>")
+ || die($DBI::errstr . "\n");<br>
...do some work with the database in order to fill up the @array varia
+ble...

$db->disconnect;<br>

$mceObj = MCE->new(max_workers => 4,
                   input_data => \@array,
                   user_func => \&mySub);
$mceObj->run;

Best regards,
and thank you in advance
Panagiotis Mamatsis.