public Map<Operator<? extends Serializable>, Map<ColumnInfo, ExprNodeDesc>> getOpToConstantExprs() {
    return opToConstantExprs;
  }
This class implements the processor context for Constant Propagate.

ConstantPropagateProcCtx keeps track of propagated constants in a column-&gt;const map for each
operator, enabling constants to be revolved across operators.
ql/src/java/org/apache/hadoop/hive/ql/optimizer/ConstantPropagateProcCtx.java