public List<RexNode> getJoinExprs(int input) {
      return this.joinKeyExprs.get(input);
    }
JoinLeafPredicateInfo represents leaf predicate in Join condition
(conjuctive lement).<br>
<p>
JoinLeafPredicateInfo:<br>
1. Stores list of expressions from left and right child which is part of
equi join keys.<br>
2. Stores set of projection indexes from left and right child which is part
of equi join keys; the indexes are both in child and Join node schema.<br>
ql/src/java/org/apache/hadoop/hive/ql/optimizer/calcite/HiveCalciteUtil.java