If I just need 2/3 columns and I query
SELECT * instead of providing those columns in select query, is there any performance degradation regarding more/less I/O or memory?
The network overhead might be present if I do select * without a need.
But in a select operation, does the database engine always pull atomic tuple from the disk, or does it pull only those columns requested in the select operation?
If it always pulls a tuple then I/O overhead is the same.
At the same time, there might be a memory consumption for stripping out the requested columns from the tuple, if it pulls a tuple.
So if that's the case, select someColumn will have more memory overhead than that of select *