Hive如何执行查询？

Question

Hive接受SQL之类的查询。在幕后，如何执行查询？它与RDBMS如何执行SQL查询相同吗？

Answer 1

Hive查询处理与标准RDBMS有很大的相似之处和不同之处。

一些关键的相似之处：

Support for a SQL  grammar. Though not full ANSI SQL 92 it is a fair subset.
Query Parser
Query Optimizer
Execution planner

一些关键的差异：

Support for HDFS loading and features
Hive specific functions such as explode, regexp_*, split
Accepting/ processing Hadoop / Cluster configuration/tuning parameters
Managing Input/Output Formats such as for HDFS, S3, Avro, etc
Creation of DAG of Map/Reduce stages/jobs
Coordination with JobTracker for Management of Map/Reduce jobs including job lifecyle: submission /monitoring /