Does setState re-renders only render() function or whole class is executed once again from scratch?

    class Sample extends Component {
          constructor(props) {
              super(props);
          this.onLoad()
     }
     
     onLoad() {
          //Some Data fetching
     }
    

     render() {
        return <Text>Sample Class</Text>;
     }
  }

if I call setState() at some point in my class is my onLoad() function is going to be called?

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