Thanks, the code is a little mess, here is how I understand it: The executor from `final RexExecutor executor = Util.first(cluster.getPlanner().getExecutor(), RexUtil.EXECUTOR)` is mainly used to construct the RexSimplify, in the RexSimplify, the expression that we evaluate is what we can make sure RexUtil.EXECUTOR can resolve(if you check the code, it only reduce the literals).
But the expressions in the ReduceExpressionsRule may be more complex, somehow we must relay on the engine to plugin their RexExecutor to make a constant reduction(some engine use code generation, some use Java reflection). So, in total, the executor in RexSimplify has a fallback is because it’s expression to reduce is simple enough. Best, Danny Chan 在 2020年3月16日 +0800 PM3:57，JiaTao Tao <[email protected]>，写道： > In method reduceExpressionsInternal, we get RexExecutor from cluster, it can > be null: > <> > > But in the outside(reduceExpressions), `final RexExecutor executor = > Util.first(cluster.getPlanner().getExecutor(), RexUtil.EXECUTOR)`, it can't > be null. > > And reduceExpressions is the only caller of reduceExpressionsInternal, so I > think this is an inconsistent behavior. > > IMHO, we should create RexUtil.EXECUTOR if it is null in > reduceExpressionsInternal, or just get RexExecutor from RexSimplify. > <> > > Regards! > Aron Tao
