I can UNLOAD data from RAM to persistance storage using the command
and I can reload it using the command
load schema.tablename1 ALL ; or load schema.tablename1 column1, column 2 ..)
Is there any way I do selective LOAD of data based on a condition ...
LOAD schema.table1 column 1, column2 where column2='2010'
If you execute the statement SELECT column 1, column 2 from table where 'condition'; then it will partially load the table to the memory.
You can check this in the m_cs_tables in main memory size and loaded column.
For the partially loaded memory, the loaded column will contain value as PARTIAL.
what you say is CORRECT , but would prefer a more elegant way to doing it rather than running a actual select query.
The idea is suppose we load data for the last 10 years at the begining and then after doing some initial sampling and reports , we only use the current and past 4 years of historical data .
Just so we dont run out of RAM space , we dont want to load the first 5 years , but just the last 5 years into the RAM but nor do we want to delete them from the persistence storage area .
why would you want to partially unload data from RAM?
Do you do that on other DBMS as well? Removing cached blocks from the db cache?
Also, be aware that once you start modifying data in any column store table and eventually a delta merge needs to be performed, the unloaded data needs to be re-loaded to memory again.
Apart from that, HANA already employs a automatic unloading of less used data in case of memory shortage.