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.\" ========================================================================
.\"
.IX Title "DBIAgent::Helper 3pm"
.TH DBIAgent::Helper 3pm "2018-07-08" "perl v5.26.2" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
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.SH "NAME"
POE::Component::DBIAgent::Helper \- DBI Query Helper for DBIAgent
.SH "SYNOPSYS"
.IX Header "SYNOPSYS"
.Vb 2
\& use Socket qw/:crlf/;
\& use POE qw/Filter::Line Wheel::Run Component::DBIAgent::Helper/;
\&
\& sub _start {
\&     my $helper = POE::Wheel::Run \->new(
\&             Program     => sub {
\&                 POE::Component::DBIAgent::Helper\->run($self\->{dsn},
\&                                                       $self\->{queries}
\&                                                      );
\&             },
\&             StdoutEvent => \*(Aqdb_reply\*(Aq,
\&             StderrEvent => \*(Aqremote_stderr\*(Aq,
\&             ErrorEvent  => \*(Aqerror\*(Aq,
\&             StdinFilter => POE::Filter::Line\->new(),
\&             StdoutFilter => POE::Filter::Line\->new( Literal => CRLF),
\&             StderrFilter => POE::Filter::Line\->new(),
\&            )
\&      or carp "Can\*(Aqt create new DBIAgent::Helper: $!\en";
\&
\& }
\&
\& sub query {
\&      my ($self, $query, $package, $state, @rest) = @_;
\&
\&      $self\->{helper}\->put(join \*(Aq|\*(Aq, $query, $package, $state, @rest);
\& }
\&
\& sub db_reply {
\&    my ($kernel, $self, $heap, $input) = @_[KERNEL, OBJECT, HEAP, ARG0];
\&
\&    # $input is either the string \*(AqEOF\*(Aq or a Storable object.
\&
\& }
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
This is our helper routine for DBIAgent.  It accepts queries on \s-1STDIN,\s0
and returns the results on \s-1STDOUT.\s0  Queries are returned on a
row-by-row basis, followed by a row consisting of the string '\s-1EOF\s0'.
.PP
Each row is the return value of \f(CW$sth\fR\->fetch, which is an arrayref.
This row is then passed to Storable for transport, and printed to
\&\s-1STDOUT.\s0  \s-1HOWEVER,\s0 Storable uses newlines (\*(L"\en\*(R") in its serialized
strings, so the Helper is designed to use the \*(L"network newline\*(R" pair
\&\s-1CR LF\s0 as the line terminator for \s-1STDOUT.\s0
.PP
When \fIfetch()\fR returns undef, one final row is returned to the calling
state: the string '\s-1EOF\s0'.  Sessions should test for this value \s-1FIRST\s0
when being invoked with input from a query.
.SS "Initialization"
.IX Subsection "Initialization"
The Helper has one public subroutine, called \f(CW\*(C`run()\*(C'\fR, and is invoked
with two parameters:
.IP "The \s-1DSN\s0" 4
.IX Item "The DSN"
An arrayref of parameters to pass to \s-1DBI\-\s0>connect (usually a dsn,
username, and password).
.IP "The Queries." 4
.IX Item "The Queries."
A hashref of the form Query_Name => \*(L"$SQL\*(R".  See
POE::Component::DBIAgent for details.
.SH "BUGS"
.IX Header "BUGS"
I have \s-1NO\s0 idea what to do about handling signals intelligently.
Specifically, under some circumstances, Oracle will refuse to
acknowledge \s-1SIGTERM\s0 (presumably since its libraries are non-reentrant)
so sometimes \s-1SIGKILL\s0 is required to terminate a Helper process.
.SH "AUTHOR"
.IX Header "AUTHOR"
This module has been fine-tuned and packaged by Rob Bloodgood
<robb@empire2.com>.  However, most of the code came directly
from Fletch <fletch@phydeaux.org>, either directly
(Po:Co:DBIAgent:Queue) or via his ideas.  Thank you, Fletch!
.PP
However, I own all of the bugs.
.PP
This module is free software; you may redistribute it and/or modify it
under the same terms as Perl itself.