Neo4j的Perl语言OGM映射工具——REST::Neo4p

jieforest

Retrieve and query

The REST::Neo4p module itself contains a few methods for retrieving database items directly. The most useful is probably get_index_by_name. Index objects have find_entries for retrieving the items in the index.

1. 1.use REST::Neo4p;
   
2. 2.use strict;
   
3. 3.use warnings;
   
4. 4.
   
5. 5.REST::Neo4p->connect('http://127.0.0.1:7474');
   
6. 6.my $idx = REST::Neo4p->get_index_by_name('nt_names','node');
   
7. 7.my ($node) = $idx->find_entries(fullname => 'adenine');
   
8. 8.my @nodes = $idx->find_entries('fullname:*');

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jieforest

Note that find_entries always returns an array, and it supports either an exact search or a lucene search.

REST::Neo4p also supports the CYPHER query REST API. Entities are returned as REST::Neo4p objects. Query results are always sent to disk, and results are streamed via an iterator that is meant to imitate the commonly used Perl database interface, DBI.

Here we print a table of nucleotide pairs that are involved in transversions:

1. 01.my $query = REST::Neo4p::Query->new(
   
2. 02.'START r=relationship:nt_mutation_types(mut_type = "transversion")
   
3. 03.MATCH a-[r]->b
   
4. 04.RETURN a,b'
   
5. 05.);
   
6. 06.$query->execute;
   
7. 07.while (my $result = $query->fetch) {
   
8. 08.print $result->[0]->get_property('name'),'->',
   
9. 09.$result->[1]->get_property('name'),"\n";
   
10. 10.}

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The query is created with the CYPHER code, then executed. The fetch iterator retrieves the returned rows (as array references) one at a time until the result is exhausted. Again, the result is not held in memory, so queries returning many rows should not present a big problem.

jieforest

Production-quality Features

My goal for REST::Neo4p is to go beyond the Perl experiments with Neo4j that are out there to create modules that are robust enough for production use (yes, people DO use Perl in production!). This meant a couple of things:

1. Be robust and feature-rich enough that people will want to try it.

2. Be responsive enough to bugs that people will see it maintained.

3. Incorporate unit and integration tests into the user installation.

4. Have complete documentation with tested examples.

5. Create bindings to as many of the Neo4j REST API functions as is possible for a guy with a real job.

6. Be concerned with performance by being sensitive to memory use, and taking advantage of streaming and batch capabilities.

7. Capture both Perl and Neo4j errors in a catchable way.

jieforest

There isn't space here to discuss these points in detail, but here are some highlights and links:

1. REST::Neo4p::Agent is the class where the REST calls get done and the endpoints are captured. It subclasses the widely-used LWP::UserAgent and can be used completely independently of the object handling modules, if you want to roll your own Neo4j REST interface.

2. The batch API can be used very simply by including the REST::Neo4p::Batch mixin. Visit the link for detailed examples.

3. When paths are returned by CYPHER queries, they are rolled up into their own simple container object REST::Neo4p::Path that collects the nodes and relationships with some convenience methods.

jieforest

You can choose to have REST::Neo4p create property accessors automatically, allowing the following:

1. 1.$node->set_property( name => 'Fred' );
   
2. 2.print "Hi, I'm ".$node->name;

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REST::Neo4p::Index allows index configuration (e.g., fulltext lucene) as provided by the Neo4p REST API.

I hope Perlers will give REST::Neo4p a try and find it useful. Again, I appeciate the time you take to report bugs.

jieforest

over.