Monday, 11 January 2016

The GraphBlogGraph: 2nd blogpost out of 3

Importing the GraphBlogGraph into Neo4j

In the previous part of this blog-series about the GraphBlogGraph, I talked a lot about creating the dataset for creating what I wanted: a graph of blogs about graphs. I was able to read the blog-feeds of several cool graphblogs with a Google spreadsheet function called “ImportFEED”, and scrape their pages using another function using “ImportXML”. So now I have the sheet ready to go, and we also know that with a Google spreadsheet, it is really easy to download that as a CSV file:

You then basically get a URL for the CSV file (from your browser’s download history):

and that gets you ready to start working with the CSV file:

I can work with that CSV file in Cypher’s LOAD CSV command, as we know. All we really need is to come up with a solid Graph Model to do what we want to do. So I went to Alistair’s Arrows, and drew out a very simple graph model:



So that basically get’s me ready to start working with the CSV files in Cypher. Let’s run through the different import commands that I ran to do the imports. All of those are on github of course, but I will take you through them here too...

First create the indexes

create index on :Blog(name);
create constraint on (p:Page) assert p.url is unique;

Then manually create the blog-nodes:

create (b:Blog {name:"Bruggen", url:"http://blog.bruggen.com"});
create (n:Blog {name:"Neo4j Blog", url:"http://neo4j.com/blog"});
create (n:Blog {name:"JEXP Blog", url:"http://jexp.de/blog/"});
create (n:Blog {name:"Armbruster-IT Blog", url:"http://blog.armbruster-it.de/"});
create (n:Blog {name:"Max De Marzi's Blog", url:"http://maxdemarzi.com/"});
create (n:Blog {name:"Will Lyon's Blog", url:"http://lyonwj.com/"});

I could have done that from a CSV file as well, of course. But hey - I have no excuse - I was lazy :) … Again…

Then I can start with importing the pages and links for the first (my own) blog, which is at blog.bruggen.com and has a feed at blog.bruggen.com/feeds/posts/default:

//create the Bruggen blog entries
load csv with headers from "https://docs.google.com/a/neotechnology.com/spreadsheets/d/1LAQarqQ-id74-zxV6R4SdG7mCq_24xACXO5WNOP-2_w/export?format=csv&id=1LAQarqQ-id74-zxV6R4SdG7mCq_24xACXO5WNOP-2_w&gid=0" as csv
match (b:Blog {name:"Bruggen", url:"http://blog.bruggen.com"})
create (p:Page {url: csv.URL, title: csv.Title, created: csv.Date})-[:PART_OF]->(b);

This just creates the 20 leaf nodes from the Blog node. The fancy styff happens next, when I then read from the “Links” column, holding the “****”-separated links to other pages, split them up into individual links, and merge the pages and create the links to them. I use some fancy Cypher magic that I have also used before for Graph Karaoke: I read the cell, and then split the cell into parts and put them into a collection, and then unwind the collection and iterate through it using an index:

//create the link graph
load csv with headers from "https://docs.google.com/a/neotechnology.com/spreadsheets/d/1LAQarqQ-id74-zxV6R4SdG7mCq_24xACXO5WNOP-2_w/export?format=csv&id=1LAQarqQ-id74-zxV6R4SdG7mCq_24xACXO5WNOP-2_w&gid=0" as csv
with csv.URL as URL, csv.Links as row
unwind row as linklist
with URL, [l in split(linklist,"****") | trim(l)] as links
unwind range(0,size(links)-2) as idx
MERGE (l:Page {url:links[idx]})
WITH l, URL
MATCH (p:Page {url: URL})
MERGE (p)-[:LINKS_TO]->(l);

So this first MERGEs the new pages (finds them if they already exist, creates them if they do not yet exist) and then MERGEs the links to those pages. This creates a LOT of pages and links, because of course - like with every blog - there’s a lot of hyperlinks that are the same on every page of the blog (essentially the “template” links that are used over and over again).
And as you can see it looks a little bit like a hairball when you look at it in the Neo4j Browser:
So in order to make the rest of our GraphBlogGraph explorations a bit more interesting, I decided that it would be useful to do a bit of cleanup on this graph. I wrote a couple of Cypher queries that remove the “uninteresting”, redundant links from the Graph:

//remove the redundant links
//linking to pages with same url (eg. archive pages, label pages...)
match (b:Blog {name:"Bruggen"})<-[:PART_OF]-(p1:Page)-[:LINKS_TO]->(p2:Page)
where p2.url starts with "http://blog.bruggen.com"
and not ((b)<-[:PART_OF]-(p2))
detach delete p2;
//linking to other posts of the same blog
match (p1:Page)-[:PART_OF]->(b:Blog {name:"Bruggen"})<-[:PART_OF]-(p2:Page),
(p1)-[lt:LINKS_TO]-(p2)
delete lt;

//linking to itself
match (p1:Page)-[:PART_OF]->(b:Blog {name:"Bruggen"}),
(p1)-[lt:LINKS_TO]-(p1)
delete lt;

//linking to the blog provider (Blogger)
match (p:Page)
where p.url contains "//www.blogger.com"
detach delete p;

Which turned out to be pretty effective. When I run these queries I weed out a lot of “not so very useful” links between nodes in the graph.
And the cleaned-up store looks a lot better and workable.

If you take a look at the import script on github, you will see that there’s a similar script like the one above for every one of the blogs that we set out to import. Copy and paste that into the browser one by one, the neo4j shell, or use LazyWebCypher, and have fun:
So that’s it for the import part. Now there’s only one thing left to do, in Part 3/3 of this blogpost series, and that is to start playing around with some cool queries. Look that post in the next few days.

Hope this was interesting for you.

Cheers

Rik

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