public void setNextSpillPartition(int nextSpillPartition) {
    this.nextSpillPartition = nextSpillPartition;
  }
This conf class is a wrapper of a list of HybridHashTableContainers and some common info shared
among them, which is used in n-way join (multiple small tables are involved).
ql/src/java/org/apache/hadoop/hive/ql/exec/persistence/HybridHashTableConf.java