Hi,
I am fairly new to SAP Hana and am trying to implement an Analytical/Reporting solution on it. I have a use case for updating data in my fact table but I am facing performance issues with respect to the memory usage and execution time. Details as follows...
Fact table - Tab_A; Record Count - 1 Billion; # of columns - 70
Detail table - Tab_B; Record count - 20 million; # of columns - 5
Now I need to update the data in my Tab_A using the data from my Tab_B. Data in Tab_A is at an Order Number, Item Number granularity where as the data in Tab_B is at an Order Number granularity. For the update I need to join these two tables on Order Number and update 4 columns in Tab_A. Something like this...
UPDATE Tab_A FROM Tab_B SET Tab_A.Col1 = Tab_B.Col1..... WHERE Tab_A.OrderNumber = Tab_B.OrderNumber.
Now the size of Tab_A is 150 GB in the Memory. But as soon as I execute the UPDATE statement the delta store starts increasing and eventually goes beyond 500 GB which is the Memory size on the system. Due to this the UPDATE fails with "Out of Memory" exception. And like this I have several updates that need to be part of my process.
Request some one please help me out with this issue...