DynamicCompositeType with templates

Introduction

To get a brief background see http://www.anuff.com/2010/07/secondary-indexes-in-cassandra.html. DynamicCompositeType lets you create column name or value using multiple columns. You can also do it using String concatenation but it's just stored as UTF8Type or ByteType. Better way is to create sub columns with it's own comparators. DynamicCompositeType lets you do just that. You can do something like c.addUTF8("john").addUTF8("smith").addLong(System.currentTimeMillis()).

DynamicCompositeType with Templates

Templates are easy representation of Hector API. It's easy to use and you like it once you start using it and start comparing your existing code with template code.

Create Column Family

 create column family Composite with comparator ='DynamicCompositeType   
  (a=>AsciiType,b=>BytesType,i=>IntegerType,x=>LexicalUUIDType,l=>LongType,t=>TimeUUIDType,s=>UTF8Type,u=>UUIDType)' 
   and default_validation_class=UTF8Type and key_validation_class=UTF8Type;

"a","b" are short notation which tells Thrift which comparatorType to use. You can use all the types as mentioned above or only the ones applicable to you.

Let's Code

Create Template Object

private ColumnFamilyTemplate<String, DynamicComposite> compTemplate  =	
	         new ThriftColumnFamilyTemplate<String, DynamicComposite>(NoSQLDAOFactory.getInstance().getKeyspace(),
		"CompositeTest", StringSerializer.get(), new DynamicCompositeSerializer());

Mutations

	ColumnFamilyUpdater<String, DynamicComposite> updater = compTemplate
			.createUpdater(entity.getKey()); //get Key and create updater object

	DynamicComposite ce = null;
	
	
	for (String col : entity.getCols().keySet()) { // For all the columns for your entity
		ce = new DynamicComposite(entity.getCols().get(col).getName(), NoSQLUtils.newTimeUUID()); //create DynamicComposite object. In this case UTF8Type, UUIDType
		updater.setString(ce, entity
				.getCols().get(col).getValue());
	}
			ce = new DynamicComposite(ColumnNameType.ENTITY_TYPE.name());
			updater.setString(ce,
					EntityType.COMPOSITE.name());
	try {
		compTemplate.update(updater); //Do Final Update
		Log.info("Entity COMPOSITE " + entity.getKey());
	} catch (HectorException e) {
		e.printStackTrace();
		throw new DataSourceException(Errors.HECTOR_EXCEPTION);
	} finally {

	}

How does it look in the CLI

 => (column=s@DOB:u@bed2e481-ba35-11e0-b239-005056c00008, value=123456789, timestamp=1311980081864001)
 => (column=s@ENTITY_TYPE, value=COMPOSITE, timestamp=1311980081864002)
 => (column=s@ENTITY_TYPE:u@bed2e480-ba35-11e0-b239-005056c00008, value=COMPOSITE, timestamp=1311980081864000)

Note how it prefixes with the types defined when column family was created.

Get Call

	try {
		ColumnFamilyResult<String, DynamicComposite> res = compTemplate
				.queryColumns(entity.getKey());
		if (null == res || !res.hasResults()) {
			throw new DataSourceException(Errors.NO_RESULT);
		}
		DynamicComposite ce  = new DynamicComposite(ColumnNameType.ENTITY_TYPE.name());
		String value = null;
		value = res.getString(ce);
		
		if (!EntityType.COMPOSITE.name().equalsIgnoreCase(value)){
			throw new DataSourceException(Errors.INALID_ENTITY_KEY);
		}
		
		entity.seteType(EntityType.COMPOSITE);
		String name = null;
		for (DynamicComposite dce : res.getColumnNames()) {
		       value = res.getString(dce);
		       name = dce.getComponent(0).toString();
		       Log.info("Composite Key " + name);
		       entity.getCols().put(name,new BigTableColumn<String>(name, value));
		}
	} catch (HectorException e) {
		// do something ...
		e.printStackTrace();
		throw new DataSourceException(Errors.HECTOR_EXCEPTION);
	} finally {

	}

.getComponent(index) gets the sub column that was created in mutation step.

That's it!!

If you are not using templates and want to use them with Hector's mutators and Column Slice directly see https://github.com/edanuff/CassandraIndexedCollections. This will help you in understanding how it actually works.