What is the data model of the database?

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Data model (Data Model)

Storm uses tuple as its data model. Each tuple is a pile of values, each value has a name, and each value can be of any type. In my understanding, a tuple can be seen as a java object with no methods. Overall, storm supports all basic types, strings, and byte arrays as value class types for tuple. You can also use your own defined types as value types, as long as you implement the corresponding serializer (serializer).

Each node in the topology must define each field of the tuple it wants to emit. For example, the following bolt defines that the tuple emitted by its lock contains two fields of type doble and triple.

Publicclass DoubleAndTripleBolt implements IRichBolt {private OutputCollectorBase _ collector; @ Override

Publicvoid prepare (Map conf, TopologyContext context, OutputCollectorBase collector) {

_ collector = collector;}

@ Override

Publicvoid execute (Tuple input) {int val = input.getInteger (0)

_ collector.emit (input, new Values (val*2, val*3)); _ collector.ack (input);}

@ Override

Publicvoid cleanup () {}

@ Override

Publicvoid declareOutputFields (OutputFieldsDeclarer declarer) {

Declarer.declare (new Fields ("double", "triple");}}

The declareOutputFields method defines the fields to output: ["double", "triple"]. We'll explain the rest of this bolt later.

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