NAME

REST::Neo4p::Batch - Mixin for batch processing

SYNOPSIS

use REST::Neo4p;
use REST::Neo4p::Batch;
use List::MoreUtils qw(pairwise);

my @bunch = map { "new_node_$_" } (1..100);
my @nodes;
batch {
 my $idx = REST::Neo4p::Index->new('node','bunch');
 @nodes = map { REST::Neo4p::Node->new({name => $_}) } @bunch;
 pairwise { $idx->add_entry($a, name => $b) } @nodes, @bunch;
 $nodes[$_]->relate_to($nodes[$_+1],'next_node') for (0..$#nodes-1);
} 'keep_objs';

$idx = REST::Neo4p->get_index_by_name('node','bunch');
($the_99th_node) = $nodes[98];
($points_to_100th_node) = $the_99th_node->get_outgoing_relationships;
($the_100th_node) = $idx->find_entries( name => 'new_node_100');

DESCRIPTION

REST::Neo4p::Batch adds some syntactic sugar allowing ordinary REST::Neo4p code to be processed through the Neo4j REST batch API.

Batch mode is not supported in Neo4j version 4.0+. The methods in this module will barf.

batch {} ($action)

To execute server calls generated by REST::Neo4p code, wrap the code in a batch block:

batch {
 # create and manipulate REST::Neo4p objects
} $action;

The $action parameter must be (there is no default) one of

• 'keep_objs'

  If keep_objs is specified, any nodes, relationships or indexes returned in the server reponse will be created in memory as REST::Neo4p objects.

• 'discard_objs'

  If discard_objs is specified, Neo4j entities in the server response will not be automatically registered as REST::Neo4p objects. Of course, these objects can be retrieved from the server through object creation and other methods, outside of the batch block.

  #!perl
  # loader...
  use REST::Neo4p;
  use REST::Neo4p::Batch;
  
  open $f, shift() or die $!;
  batch {
    while (<$f>) {
     chomp;
     ($name, $value) = split /\t/;
     REST::Neo4p::Node->new({name => $name, value => $value});
    } 'discard_objs';
  exit(0);

Errors in batch jobs

batch{}() returns returns an array of REST::Neo4p::Exceptions error objects for each job that returns a server-generated error. If no errors were encountered, it returns undef.

foreach ( batch { _do_stuff() } 'discard_objs' ) {
  print STDERR $_->message, "(", $_->code, ")\n";
}

batch will warn() for each error immediately if $REST::Neo4p::VERBOSE is set.

CAVEATS

• No call to the server is made until after the block is executed. There is some magic provided, but not all object functionality is available to REST::Neo4p entities obtained within the batch block.

  For example, this works:

  my $idx = REST::Neo4p::Index->new('node' => 'pals_of_bob');
  my $name = 'fred'
  batch {
   my $node = REST::Neo4p::Node->new({name => $name});
   $idx->add_entry($node, name => $name);
  } 'keep_objs';

  but this does not:

  my $idx = REST::Neo4p::Index->new('node' => 'pals_of_bob');
  my $name = 'fred';
  batch {
   my $node = REST::Neo4p::Node->new({name => $name});
   $idx->add_entry($node, name => $node->get_property('name'));
  } 'keep_objs';

  because $node has not been created on the server at the time that add_entry() is executed, so get_property('name') fails.

SEE ALSO

REST::Neo4p, REST::Neo4p::Agent

AUTHOR

Mark A. Jensen
CPAN ID: MAJENSEN
majensen -at- cpan -dot- org

LICENSE

Copyright (c) 2012-2021 Mark A. Jensen. This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.