Which statements are true about a prejoin projection? (Select three.)
A.
A prejoin projection enforces primary and foreign key constraints.
B.
A prejoin projection does not increase the storage footprint.
C.
A prejoin projection slows down data loading.
D.
A prejoin projection can process any type of join.
E.
A prejoin projection adds no limitations to the tables in the join.
F.
A prejoin projection improves query run time performance.
Explanation:
I am sure 2 correct answers here are:
A – https://my.vertica.com/docs/7.1.x/HTML/index.htm#Authoring/AnalyzingData/Queries/Pre-joinProjectionsAndJoinPredicates.htm?Highlight=pre-join
F – https://my.vertica.com/docs/7.1.x/HTML/index.htm#Authoring/Glossary/Pre-joinProjection.htm?Highlight=pre-join
For the 3rd one,
I know it is not D, because the only INNER JOINs are allowed – https://my.vertica.com/docs/7.1.x/HTML/index.htm#Authoring/Glossary/Pre-joinProjection.htm?Highlight=pre-join
I believe it is not E, because at least one of limitation is – Do not apply partitioning to tables used as dimension tables in pre-join projections –
https://my.vertica.com/docs/7.1.x/HTML/index.htm#Authoring/AdministratorsGuide/Partitions/DefiningPartitions.htm?Highlight=pre-join
I do believe B is not as well true – It should increase the storage footprint, because it is materialization of join in fact.
So finally I have A, C, F
Any thoughts ?
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A and F exactly correct.
I think so the other correct option C.
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