presto-main/src/main/java/io/prestosql/operator/OperatorContext.java/OperatorContext/recordAddInput
class OperatorContext:    void recordAddInput(OperationTimer operationTimer, Page page)
    {
        operationTimer.recordOperationComplete(addInputTiming);
        if (page != null) {
            inputDataSize.update(page.getSizeInBytes());
            inputPositions.update(page.getPositionCount());
        }
    }