Limit for Projections

NarayanV

Hi,

 

   In the vertica knowldge base, I got the pdf which talks TUPLE  MOVER . In the   best practice for Mergeout section  , I see th below statments "Do not have more than two projection sets anchored on the same table.". What is the exact meaning of this, is it recommending that we should not create more than two projections for a table. Please clarify.

 

Link I refered as below

https://community.dev.hpe.com/t5/Vertica-Knowledge-Base/Tuple-Mover-Best-Practices/ta-p/235261#_Toc445990864

eli_revach

HI ,

There is no hard limit on the amount of projections per table , in most of the cases 2 (super)  projections per table  can address most of the use cases . however each projection had an overhead to database in required more cluster resources , some examples :

1. Data load – Like indexes in other databases , projections  are full  sync within the commit  ,   more projections will required  more  CPU , memory and IO for doing that  .
2. TUPLE MOVER and Mergeout  are the background process that normalized the underline  data files , more projections = more data files = more resource .

 To summertize , you can have more then 2 projections per table ,  but be careful  , your cluster is going to work hard , and you will not necessarily  gain many .

 

I hope you will find it useful

 

Thanks

NarayanV

Hi ,

 

  Thanks for your explanation.