presto-main/src/main/java/io/prestosql/operator/scalar/MapElementAtFunction.java/MapElementAtFunction/elementAt
class MapElementAtFunction:    @UsedByGeneratedCode
    public static Object elementAt(MethodHandle keyEqualsMethod, Type keyType, Type valueType, Block map, Object key)
    {
        SingleMapBlock mapBlock = (SingleMapBlock) map;
        int valuePosition = mapBlock.seekKeyExact((Block) key);
        if (valuePosition == -1) {
            return null;
        }
        return readNativeValue(valueType, mapBlock, valuePosition);
    }