Does fetch plan actually have any effect when working with OrientVertex/ODocument in remote mode?

[Jan Plaček]

Consider tree like graph represented by "Node" verticies and "childOf" edges (oriented from child to parent) and command:

Iterable<OrientVertex> roots = (Iterable<OrientVertex>) graph.command(new OCommandSQL("select from Node where key = 'root'  fetchplan in_childOf:-1")).execute();

Now when I traverse the tree by Vertex.getVerticies(Direction.IN, "childOf")/ODocument.field("in_childOf") I expect there won't be any further remote lookup calls, because verticies have been already fetched by fetch plan.

But is it really the case?

I was trying to find out how accessing related records (edges) works:

The edges are represented as ORidBag:

ORidBag ridBag = (ORidBag) root.getRecord().field("in_childOf");

The ORidBag is a collection of OIdentifiable implemented by ORecordId:

ORecordId rid = (ORecordId) ridBag.iterator().next();

Now I can access the record (implemented by ODocument) representing the edge:

ODocument inChild = (ODocument) rid.getRecord();

The implementation of ORecordId.getRecord() is quite simple. It basically delegates the record retrieval to current ODatabaseDocument implemented by ODatabaseDocumentTx:

return (T) db.load(this);

There the things are getting complicated, but if I summarize my foundings, the record is either taken from local cache or requested to be fetched by OStorageRemote.

As you can see I was able to find out only one place where the related record is not requested from the storage again and that is obtaining a record from local cache by ODatabaseDocumentTx.

However I checked that the related records are not present in local cache after the command is executed, so local cache also isn't responsible for accessing eagerly fetched records.

So am I really working with fetched records or are they fetched again when traversing graph with Document/Graph API in remote mode?

Which component (ODocument/ORidBag/ODatabase/OStorage) is responsible for obtaining a record which is possibly loaded eagerly via fetch plan? 

And is there a way to tell if the related record (represented for example by ORecordId) is already fetched?

UPDATE:

According to some forum posts the eagerly fetched records should be stored in 2nd level client cache, I wonder how do I access that cache?

UPDATE2:

Since orientdb 2.0, there is only one local cache, but as I mentioned earlier, it does not contain the verticies/edges after the command is executed (they are present in the cache only after I visit them manually - via traversal methods), is this unexpected behavior?

[Jan Plaček]

Can someone please test and confirm that using fetchplan does not place any additional records into a local cache? (with transacational database in remote mode).

You can test for record presence in a local cache like this:

graph.getRawGraph().getLocalCache().findRecord(new ORecordId("#11:0")) != null;

Dne středa 23. září 2015 23:52:13 UTC+2 Jan Plaček napsal(a):

Consider tree like graph represented by "Node" verticies and "childOf" edges (oriented from child to parent) and command:

Iterable<OrientVertex> roots = (Iterable<OrientVertex>) graph.command(new OCommandSQL("select from Node where key = 'root'  fetchplan in_childOf:-1")).execute();

Now when I traverse the tree by Vertex.getVerticies(Direction.IN, "childOf")/ODocument.field("in_childOf") I expect there won't be any further remote lookup calls, because verticies have been already fetched by fetch plan.

But is it really the case?

I was trying to find out how accessing related records (edges) works:

The edges are represented as ORidBag:

ORidBag ridBag = (ORidBag) root.getRecord().field("in_childOf");

The ORidBag is a collection of OIdentifiable implemented by ORecordId:

ORecordId rid = (ORecordId) ridBag.iterator().next();

Now I can access the record (implemented by ODocument) representing the edge:

ODocument inChild = (ODocument) rid.getRecord();

The implementation of ORecordId.getRecord() is quite simple. It basically delegates the record retrieval to current ODatabaseDocument implemented by ODatabaseDocumentTx:

return (T) db.load(this);

There the things are getting complicated, but if I summarize my foundings, the record is either taken from local cache or requested to be fetched by OStorageRemote.

As you can see I was able to find out only one place where the related record is not requested from the storage again and that is obtaining a record from local cache by ODatabaseDocumentTx.

However I checked that the related records are not present in local cache after the command is executed, so local cache also isn't responsible for accessing eagerly fetched records.

So am I really working with fetched records or are they fetched again when traversing graph with Document/Graph API in remote mode?

If yes, which component (ODocument/ORidBag/ODatabase/OStorage) is responsible for obtaining a record which is possibly loaded eagerly via fetch plan?