Can someone through some light , in case we get 5-6hrs downtime for this change , then what method should we choose for this Alter operation?
We can't really answer that. Only you know what resources you have, what risk/reward you are willing to handle, and how long things may take. For that latter item, your best bet is to try this out on the same/similar hardware and see how long it takes. Do a smaller table and extrapolate if you need to.
Hello Greg,
In terms of testing on sample data and extrapolating, as i picked the avg partition sizeof the table (which is ~20GB) and i created a non partitioned table with exactly same columns and populated with similar data and also created same set of indexes on it and the underlying hardware is exactly same as its on production. I am seeing it's taking ~5minutes to alter all the four columns on this table. So we have ~90 partitions in production with data in them and the other few are future partitions and are blank. (Note- I executed the alter with "work_mem=4GB, maintenance_work_mem=30gb, max_parallel_worker_per_gather=8, max_parallel_maintenance_worker =16" )
So considering the above figures , can i safely assume it will take ~90*5minutes= ~7.5hours in production and thus that many hours of downtime needed for this alter OR do we need to consider any other factors or activity here?
