Hi,
(I might have errors in the CQL, Cassandra schema and the functions need
proper escaping)
Example 1:
Zero depth tree wiht UUID as the rowid or key.
URL /content/cassandra/pictures/13f58d5c95c70b6f
then the column family is pictures and the URL -> ROWID function just
results in the ROWID being 13f58d5c95c70b6f and
String cql = mapOfCassandraMappers.get("pictures").getCQL("pictures", "
13f58d5c95c70b6f")
System.err.println(cql);
where
String getCQL(String cf, String path) {
return "select * from "+cf+" where rowid = '"+path+"'";
}
yields:
select * from pictures where rowid = '13f58d5c95c70b6f'
13f58d5c95c70b6f would be generated by the application when the user
created a new picture (by upload).
Example 2:
User specified
URL /content/cassandra/catalogue/capacitors/electrolytic/axial/16v/10uf
String cql = mapOfCassandraMappers.get("catalogue").getCQL("catalogue", "
capacitors/electrolytic/axial/16v/10uf")
System.err.println(cql);
where
String getCQL(String cf, String path) {
MessageDigest md = MessageDigest.getInstance("SHA1");
String rowID = Base64.encode(md.finish(path.getBytes("UTF-8")));
return "select * from "+cf+" where rowid = '"+rowID+"'";
}
yields
select * from pictures where rowid = 'NzdlZmU4OTZmNGM4MzMwYzZ'
If you want to find the parent then
mapOfCassandraMappers.get("catalogue").getCQL("catalogue", "
capacitors/electrolytic/axial/16v")
select * from pictures where rowid = 'ZGFzZGZzZnNkYWZzYWRmc2R'
And if the parent is stored in the property parent then
select * from pictures where parent = 'ZGFzZGZzZnNkYWZzYWRmc2R'
will generate a list of children. (Not sure about performance)
Example 3:
User is allowed to enter the RowID directly (identical to Example 1
URL
/content/cassandra/cannesfilmfestival/TomCruiseCassino-20130402112345-ieb.jpg
where
String getCQL(String cf, String path) {
return "select * from "+cf+" where rowid = '"+path+"'";
}
yields:
select * from pictures where rowid = '
TomCruiseCassino-20130402112345-ieb.jpg'
Does that make sense ?
Ian
On 25 June 2013 05:29, Dishara Wijewardana <ddwijeward...@gmail.com> wrote:
> On Mon, Jun 24, 2013 at 4:02 AM, Ian Boston <i...@tfd.co.uk> wrote:
>
> > Hi Dishara,
> > Yes. 1 resource == 1 row.
> > The columns within that row represent the properties of the resource.
> > I suggest that you use standard property names where appropriate (eg
> > sling:resourceType is the Resource.resourceType etc)
> >
> > The Resource itself should be adaptable to a generic CassandraResource
> > (which will probably implement Resource) which will have a map of
> > properties containing all the columns of the cassandra row. (optimise
> > later) A CassandraResource might look and feel like a Map<String, Object>
> > or it might have a Map<String, Object> getProperties() method, or better
> > still be adaptable to a Map. The essential think is dont hard code the
> > property names in the interface of CassandraResource for the moment. ie
> no
> > getContentType() and no getMimeType(), as we dont really know what a
> > CassandraResource will store.
> >
> > ResourceMetadata should be built from a subset of the CassandraResource
> > properties.
> >
> > You won't need to implement a ResourceResolver, only a ResourceProvider
> > (and Factory). I would use CQL in preference to other API methods.
> >
> > There is one thing that hasnt been mentioned, and thats the URL ->
> > Cassandra Row mapping.
> > There are several ways of doing this.
> >
> > eg:
> > URL = /content/cassandra/<columnFamily>/<rowID>
> > Cassandra Column Family = columnFamily
> > Cassandra RowID = rowID
> > or
> > URL = /content/cassandra/<columnFamilySelector>/remainder/of/the/path
> > Cassandra Cassandra Column Family =
> > mapOfColumnFamilies.get(columnFamilySelector)
> > Cassandra RowID = function(/remainder/of/the/path)
> >
> > or to take that one stage further
> >
> > public interface CassandraMapper {
> > String getCQL(String columnFamilySelector, String path);
> > }
> >
> Hi Ian
> Thank you for the detailed explanation.
>
> OK. +1 for this approach with the mentioned flexibility.But I need a small
> clarification. With this approach,
>
> URL = /content/cassandra/<columnFamilySelector>ROW-ID
> ROW-ID - function(/remainder/of/the/path).
> So you mean ROW-ID is something we have to programatically uniquely create
> right ? like a UUID.
>
> What is this "/remainder/of/the/path" means ? Can you give an example with
> real values in the context of a user who want to obtain a resource from
> cassandra.
> This is just for my understanding.
>
>
>
> >
> > URL = /content/cassandra/<columnFamilySelector>/<remainderOfPath>
> >
> > String cqlQuery =
> >
> >
> mapOfCassandraMappers.get(columnFamilySelector).getCQL(columnFamilySelector,
> > remainderOfPath);
> >
> > Which would allow us provided one or more implementations of
> > CassandraMapper to map between URL and CQL.
> >
> >
> > HTH
> > Ian
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> > On 23 June 2013 19:29, Dishara Wijewardana <ddwijeward...@gmail.com>
> > wrote:
> >
> > > Hi Ian,
> > >
> > > What is the data mapping should be between Cassandra and Sling
> resource.
> > I
> > > mean is a Sling Resource maps to a Cassandra Column ? Or Column Family
> ?
> > >
> > > Because to get this Cassandra and Sling story correct we need to
> finalize
> > > this.
> > > For an example what we eventually returns is a Sling resource.
> Everything
> > > that needs to fill in to create Sling resource should be stored in
> > > Cassandra.
> > > In a Sling resource,
> > >
> > > - Path - direct sling resource path
> > > - ResourceType - nt:cassandra
> > > - ResourceSuperType - ?
> > > - ResourceMetadata - we can create this on the fly with the data
> from
> > > the corresponding column. At insertion, those need to be stored.
> > > Following
> > > are the ones which I thought might be useful by default to be set
> for
> > > any
> > > node. Please add if we need anything more.
> > > - ContentType
> > > - ContentLength
> > > - CreationTime
> > > - ModificationTime
> > > - ResourceResolver - Do we need a resolver in this case ?
> > >
> > >
> > > So I believe in CQL context, one ROW should represent a Sling
> resource.
> > If
> > > that is the case for ResourceMetadata we might need a separate column
> to
> > > store it since it has multiple values. I am not sure whether we can do
> it
> > > with CQL, but it should be possible with hector APIs may be.
> > >
> > > Appreciate your thoughts ?
> > >
> > >
> > > On Wed, Jun 19, 2013 at 1:19 AM, Dishara Wijewardana <
> > > ddwijeward...@gmail.com> wrote:
> > >
> > > > Hi Ian,
> > > > I am starting this thread to keep track on things related to the GSoC
> > > > project related milestone status updates and related discussions.
> > > > So the first task over view will be as follows as per GSoC proposal
> > > > provided.
> > > >
> > > > 1. Implementing a CassandraResourceProvider to READ from Cassandra.
> > > > Implementation Details [1]
> > > >
> > > >
> > > >
> > > > [1] : Implementation Details:
> > > >
> > > > 1.A) Write a CassanrdaResourceProviderUtil which is basically a
> > > > cassendra client which will facilitate all cassandra related
> operations
> > > > required by other modules (CassandraResourceProvider and
> > > > CassandraResourceResolver).
> > > >
> > > > 1.B) Implementation of CassandraResourceProvider
> > > >
> > > > 1.C) Implementation of CassandraResourceResolver
> > > >
> > > > 1.D) Implementation of CassandraResource
> > > >
> > > >
> > > > And I will start writing the CassanrdaResourceProviderUtil class
> which
> > > > will do basic add and get using hector API. Please provide any
> feedback
> > > > that will be useful to accomplish this task.
> > > > So for this how does path mapping should be done. Because for
> example,
> > > the
> > > > path of the cassendra node will not be same as the jcr node path. i.e
> > > > provider will ask a node path /system/myapps/test/foo and where
> should
> > we
> > > > return it from Cassandra. Aren't we have to first consider the WRITE
> > > aspect
> > > > to Cassandra ?
> > > >
> > > >
> > > > --
> > > > Thanks
> > > > /Dishara
> > > >
> > >
> > >
> > >
> > > --
> > > Thanks
> > > /Dishara
> > >
> >
>
>
>
> --
> Thanks
> /Dishara
>
