Partitions and ROS containers

SRA1

What is the relation between Partitions and ROS containers?

How will it impact performance of database

eli_revach

Hi In short ,

Partition gave you addition slice to your data , in Vertica the data is segmented (divided ) a cross the nodes , partition gave addition   slice storage  capability’s in level of host .

 

In some case it can improved  your query performances . The main used of  them is for purging data as Vertica is not so optimized for deletes .

 

Amount of partitions is limited  (up to the maximum amount of ROS containers- 1024)  , but in fact it should be much more less , best practices is around  200-300   .

 

ROS files are manage per partitions , Mergout have different roles with regard to active and none active partitions

 

 

  Thanks

SRA1

Thanks but I wanted to know how the partitioned created in vertica has to do with ROS container and What happens when a new ROS container created from move out has to follow up with partition.

eli_revach

See more info about Partition  & ROS file 

https://community.dev.hpe.com/t5/Vertica-Forum/Understanding-table-partitions-and-ROS-containers/td-p/206021

 

 

About MoveOut  - its in the same game , if your data in the WOS  belong  to specific partition the MoveOut  will create ROS file for this partition  and will increases your total ROS file per projection  

 

I hope it answer your question

 

Thanks

 

SRA1

I have a table with year-week combination as partition which means there will be 54 partitions per year.

The current date is 12-jan-2016 the partition would be 201603 .

we have some data for current partition and ROS file associated with that.

If I load data say 1000 records using 10 inserts (100 in each insert) in WOS.

Will the moveout move all 1000 records in the existing ROS for the partition or creates a new ROS file?

How the moveout will copy the 10 bits of data to ROS?

eli_revach

Hi ,

In Vertica Transactions  never update existing ROS files , MoveOut will create new ROS file for all the 10 different transactions  on the 201603 partition .

 

You can see MoveOut as a process that do WOS Mergout and create singel ROS file  as an output .

 

I hope this answer your question

Thanks 

 

SRA1

Hi , Thanks for answering patiently .

So You are mentioning that the 1000 records will be moved to One newly created ROS container file.

in that case there will be morethan one ROS file for one partition.

  Now the new question in that case is "Will the mergeout merge the 2 ROS files and combine it to one or the multi ROS for one partiotion still persists"

eli_revach

Correct , you can have  more than one ROS  file in an active partition , for none active partition , you will have only one .

During the life of the partition (the time its in active partition mode) Mergout will try to merge the ROS files to minimum amounts ( Its more of the algorithm of the Mergout) , but it not necessarily  that you will have only one.

 

Thanks  

 

SRA1

wonderful.. Thankyou Verymuch :-)