[HIVE-4960] lastAlias in CommonJoinOperator is not used

• Type: Improvement
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Fix Version/s: 0.12.0
• Assignee: Yin Huai
• Reporter: Yin Huai
• Created: 30/Jul/13 20:18
• Updated: 15/Oct/13 23:29
• Resolved: 01/Aug/13 16:10

Description

In CommonJoinOperator, there is object called lastAlias. The initial value of this object is 'null'. After tracing the usage of this object, I found that there is no place to change the value of this object. Also, it is only used in processOp in JoinOperator and MapJoinOperator as

if ((lastAlias == null) || (!lastAlias.equals(alias))) {
  nextSz = joinEmitInterval;
}

Since lastAlias will always be null, we will assign joinEmitInterval to nextSz every time we get a row. Later in processOp, we have

nextSz = getNextSize(nextSz);

Because we reset the value of nextSz to joinEmitInterval every time we get a row, seems that getNextSize will not be used as expected.