why ROS_COUNT is 2

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why ROS_COUNT is 2

Post by Mrao » Wed Feb 12, 2014 9:28 pm


I inserted data into a table from another table using the below statement. The table structure and rowcount of both the structures is the same, but ros_count on projection_storage is different. The source table ros_count is 1 and the target tbale ros_count is 2. Any idea why it is different?

insert /* + direct */ into test.online_sales_fact select * from online_sales.online_sales_fact

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Re: why ROS_COUNT is 2

Post by NorbertKrupa » Wed Feb 12, 2014 9:33 pm

Are the projections identical? It seems to me that the number of ROS containers would be optimized based on the number of projections. Some other thoughts from the documentation:
A ROS (Read Optimized Store) container is a set of rows stored in a particular group of files. ROS containers are created by operations like Moveout or COPY DIRECT, and can be observed in the STORAGE_CONTAINERS system table. The ROS container layout can differ across nodes due to data variance. Segmentation can deliver more rows to one node than another. Two loads could fit in the WOS on one node and spill on another.
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