DRILL-8513: Right Hash Join with empty Left table ruturns 0 result

[rymarm]

DRILL-8513: Right Hash Join with empty Left table ruturns 0 result

Description

Drill returns no results on the right Hash Join if the probe(left) table is empty.

The root cause is simple. Stack-trace of the point of failure:

changeToFinalProbeState:123, HashJoinProbeTemplate (org.apache.drill.exec.physical.impl.join)
setup:105, ProbeTemplate (org.apache.drill.exec.physical.impl.join) <---- The issue comes from here. Because the changeToFinalProbeState() is called before all necessary variables are initialized by the HashJoinProbeTemplate#setup() method.  
setup:45, HashJoinProbeTemplate (org.apache.drill.exec.physical.impl.join) 
setupProbe:108, HashJoinBatch (org.apache.drill.exec.physical.impl.join)
innerNext:585, AbstractHashBinaryRecordBatch (org.apache.drill.exec.physical.impl.join)

HashJoinProbeTemplate#setup() calls it's super #setup() before joinType set and it makes #changeToFinalProbeState() set incorrect ProbeState. This code change comes from #2599

The solution is as simple as the bug: to call ProbeTemplate#setup() at the end of HashJoinProbeTemplate#setup().

Documentation

-

Testing

New unit test with an empty left input for HashJoin.

[cgivre]

LGTM +1