What is the execution process of MapReduce tasks in Hive
The execution process of MapReduce tasks in Hive is as follows:
- Hive queries are translated into HiveQL and then transformed into MapReduce jobs.
- Hive submits MapReduce jobs to the YARN ResourceManager of the Hadoop cluster.
- The YARN ResourceManager allocates resources for the job and initiates the corresponding Map and Reduce tasks.
- The Map task reads input data from HDFS, splits it, and then passes it to the Map function for processing.
- The Map function transforms input data into key-value pairs, processes them to generate intermediate results, and then writes these intermediate results to the local disk.
- The Reduce task reads data from intermediate results generated by Map tasks, merges and summarizes values for the same key, and writes the final result to HDFS.
- The final result will be returned to the Hive client, allowing users to access the query results through Hive.
Overall, the execution process of MapReduce tasks in Hive is similar to regular MapReduce tasks. The difference lies in the fact that in Hive, users can write query statements using HiveQL, which are then converted by Hive into MapReduce jobs for execution.
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