How does JanusGraph/Titan Database interact with cassandra?

[i...@zju.edu.cn]

I'm trying to understand how JanusGraph/Titan interact with Cassandra. Specifically, I want to know what Cassandra tables does JanusGraph/Titan create, what contents are in them and what happens to them when I mutate the graph, e.g. adding a vertex, adding an edge, create an index...

After connecting to Cassandra using code below, I notice that there're 9 tables under 'titan' keyspace in Cassandra (I'm experimenting using Titan):

g=TitanFactory.build().set("storage.backend", "cassandra").set("storage.hostname","127.0.0.1").open();

Those tables are:

titan_ids

edgestore

edgestore_lock_

system_properties

system_properties_lock_

graphindex

graphindex_lock_

txlog

systemlog

I added a vertex:

john=g.addVertex("John");

And then I notice that titan_ids contains 5 new rows, and each time I add another vertex, 2 more rows appear. No other tables are affected. But if I drop any of the vertices, the rows does not disappear.

I want to know the content of those new rows, but 

select * from titan_ids;

gives:

 key                | column1

               | value

--------------------+-----------------------------------------------------------

---------------+-------

 0x0000000000000003 | 0xfffffffffffec77f00055f5c22db84f8643232303931343031323230

302d6972697331 |    0x

 0x5000000000000000 | 0xffffffffffffd8ef00055f5c22e1b300643232303931343031323230

302d6972697331 |    0x

 0x0000000000000004 | 0xffffffffffffff9b00055f5c22d658c0643232303931343031323230

302d6972697331 |    0x

 0x0000000000000004 | 0xffffffffffffffcd00055f5c22d11518643232303931343031323230

302d6972697331 |    0x

 0xe800000000000000 | 0xffffffffffffd8ef00055f5c6c828bb0643232303931343031323230

302d6972697331 |    0x

 0x5000000000000003 | 0xfffffffffffec77f00055f5c22e6df38643232303931343031323230

302d6972697331 |    0x

 0xe800000000000003 | 0xfffffffffffec77f00055f5c6c87b400643232303931343031323230

302d6972697331 |    0x

 0xa000000000000000 | 0xffffffffffffd8ef00055f5c6381f708643232303931343031323230

302d6972697331 |    0x

 0xa000000000000003 | 0xfffffffffffec77f00055f5c63872340643232303931343031323230

302d6972697331 |    0x

(9 rows)

which is not for human to read, so I have no idea what JanusGraph/Titan ask Cassandra to store. I expect to see some literals like "John".

So my question is, what do those 9 tables store? Is there any documentation about it? How can I read the contents in them so that when I experiment with Cassandra, I can understand what's going on for each table?

[Ankur Goel]

Right now deep detail is missing in doc, only information only thing available is http://docs.janusgraph.org/latest/data-model.html

 Which only talk about graph storage at high concept level  more on adjacency list concept.

Other way is to look source code.

~

[i...@zju.edu.cn]

Thanks for your reply, I'm referring to source code now.

在 2017年12月4日星期一 UTC+8下午1:14:57，Ankur Goel写道：

[Ankur Goel]

Don't forgot to share your findings here.

~

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[shivanjal arora]

Hi,

I was able to decode the edge store table data.

I have written a java code for decoding the edge store table.

The code basically connects to Cassandra Database and also creates opens a Janusgraph Instance.

Details for Cassandra server(hostname, port and keyspace) are hard coded in the file CassandraReadEdgeStoreTable.java.

Janusgraph properties are stored in a properties file and the path has to be provided at run time via command line argument.

Note:If there are partitioned vertices in your graph, this code may not work.

I have used snippets from JanusGraphVertexDeserializer class from Janusgraph project.

I have attached two files:

1. CassandraReadEdgeStoreTable.java

2. test.properties

Hope It helps!

On Saturday, December 2, 2017 at 9:22:38 PM UTC+5:30, i...@zju.edu.cn wrote:

[dengzim...@gmail.com]

you are great!

so can you give more code for decoding the graph index table and janusgraph_ids table.

[learnin...@gmail.com]

I too am interested for having a plain text visibility toggle. Is this something that must not be exposed for app developers? Am not sure or can't find good supporting information.

On Saturday, December 2, 2017 at 9:22:38 PM UTC+5:30, i...@zju.edu.cn wrote: