org.apache.hadoop.hive.ql.optimizer.unionproc
Class UnionProcFactory.UnionNoProcessFile

java.lang.Object
  org.apache.hadoop.hive.ql.optimizer.unionproc.UnionProcFactory.UnionNoProcessFile

All Implemented Interfaces:

NodeProcessor

Enclosing class:

UnionProcFactory

public static class UnionProcFactory.UnionNoProcessFile
extends Object
implements NodeProcessor

Union followed by no processing. This is to optimize queries of the type: select * from (subq1 union all subq2 ...)x; where at least one of the queries involve a map-reduce job. There is no need for a union in this scenario - it involves an extra write and read for the final output without this optimization. Queries of the form: select x.c1 from (subq1 union all subq2 ...)x where filter(x.c2); can be transformed to: select * from (subq1 where filter union all subq2 where filter ...)x; and then optimized.

Constructor Summary

UnionProcFactory.UnionNoProcessFile()

Method Summary

Object

process(Node nd, Stack<Node> stack, NodeProcessorCtx procCtx, Object... nodeOutputs) Generic process for all ops that don't have specific implementations.

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

UnionProcFactory.UnionNoProcessFile

public UnionProcFactory.UnionNoProcessFile()

Method Detail

process

public Object process(Node nd,
                      Stack<Node> stack,
                      NodeProcessorCtx procCtx,
                      Object... nodeOutputs)
               throws SemanticException

Description copied from interface: NodeProcessor

Generic process for all ops that don't have specific implementations.

Specified by:

process in interface NodeProcessor

Parameters:

nd - operator to process

procCtx - operator processor context

nodeOutputs - A variable argument list of outputs from other nodes in the walk

Returns:

Object to be returned by the process call

Throws:

SemanticException