// for projection
this.projector = new Projector(inSchema, outSchema, plan.getTargets());
this.evalContexts = projector.renew();
// for join
frameTuple = new FrameTuple();
outTuple = new VTuple(outSchema.getColumnNum());
leftKeyTuple = new VTuple(leftKeyList.length);
leftNumCols = leftChild.getSchema().getColumnNum();
rightNumCols = rightChild.getSchema().getColumnNum();