Managing Hive Slowly Changing Dimensions

Carter Shanklin shows how to manage Type 1, 2, and 3 slowly changing dimensions in Hive:

The most common SCD update strategies are:

  • Type 1: Overwrite old data with new data. The advantage of this approach is that it is extremely simple, and is used any time you want an easy to synchronize reporting systems with operational systems. The disadvantage is you lose history any time you do an update.

  • Type 2: Add new rows with version history. The advantage of this approach is that it allows you to track full history. The disadvantage is that your dimension tables grow without limit and may become very large. When you use Type 2 SCD you will also usually need to create additional reporting views to simplify the process of seeing only the latest dimension values.

  • Type 3: Add new rows and manage limited version history. The advantage of Type 3 is that you get some version history, but the dimension tables remain at the same size as the source system. You also won’t need to create additional reporting views. The disadvantage is you get limited version history, usually only covering the most recent 2 or 3 changes.

The Hive solution is getting closer and closer to a traditional relational warehouse solution.  And on the whole, that’s a good thing.

Related Posts

Flink and Stateful Streaming

Himanshu Gupta explains some of the benefits Apache Flink offers for stateful streaming applicatons: The 2 main types of stream processing done are:1. Stateless: Where every event is handled completely independent from the preceding events.2. Stateful: Where a “state” is shared between events and therefore past events can influence the way current events are processed. […]

Read More

Performance Testing Aiven Kafka

Heikki Nousiainen tests the Aiven platform’s Kafka implementation on different cloud providers at different service levels: We used a single topic for our write operations with a partition count set to either 3 or 6, depending on the number of brokers in each test cluster. As the test clusters were regular Aiven services, the partitions […]

Read More

Categories

August 2017
MTWTFSS
« Jul Sep »
 123456
78910111213
14151617181920
21222324252627
28293031