Wrong answer in Data Architect test exam

[jena-savvy007]

Hello everyone,

I was doing the test questions for the Data Architect exam when this question appeared (image below)

First of all, I didn´t know that was even possible, so I did try it myself to check it was true.

I used this script:

T_PAISES:
LOAD * INLINE
[
numero,pais
0,Spain
1,France
2,Italy
3,Poland
4,Portugal
5,Germany
6,Holand
7,China
8,USA
9,Japan
];

T_INFORMACION:
LOAD
(Floor(Rand() * (9+1-0)) + 0) AS numero,
(Floor(Rand() * (5454654-45)) + 45) AS a,
(Floor(Rand() * (7888-0)) + 0) AS b,
(Floor(Rand() * (288-0)) + 0) AS c,
RecNo() AS fila
AutoGenerate 10000000;
INNER JOIN
LOAD
*
RESIDENT T_PAISES;

DROP TABLE T_PAISES;
STORE T_INFORMACION into
[lib://Escritorio/T_INFORMACION.qvd] (qvd);
DROP TABLE T_INFORMACION;

TRACE where original;

T_WHERE_ORIGINAL:
LOAD
pais AS pais_original,
a AS a_original,
b AS b_original,
c AS c_original
FROM [lib://Escritorio/T_INFORMACION.qvd] (qvd)
WHERE pais = 'Spain';

TRACE fin original;

DROP TABLE T_WHERE_ORIGINAL;

TRACE where propuesto;

T1:
LOAD * INLINE
[
pais
Spain
];

T_WHERE_PROPUESTO:
LOAD
pais AS pais_propuesto,
a AS a_propuesto,
b AS b_propuesto,
c AS c_propuesto
FROM [lib://Escritorio/T_INFORMACION.qvd] (qvd)
WHERE Exists(pais);
DROP TABLE T1;

TRACE fin propuesto;
DROP TABLE T_WHERE_PROPUESTO;

The correct method of doing the where clause for qlik was never faster than the other one. Does anyone know why qlik says it's the optimal one?

Thank you very much in advance.

Jose

[tresesco · Accepted solution]

Third option is correct - because with that where clause data is loaded as optimized load, whereas with all the rest cases, the load is unoptimzed and in qlik optimized qvd load is much faster than non-optimzed qvd load.

For further reading: 

https://www.quickintelligence.co.uk/qlikview-optimised-qvd-loads/

https://community.qlik.com/t5/QlikView-App-Development/optimize-and-non-optimze-load-in-qvd/td-p/311...

[jena-savvy007]

Thank you very much, my lack of performance was due to I was renaming the fields on the load.

Thank you for the links, they are very useful!!