On Thu, Dec 27, 2018, at 5:23 PM, Bhavin Gandhi wrote: > Hello, > I'm trying to understand for a given unlogged table of a specific size > and # of rows, if I do "alter table" on it to convert it to logged > table, is there a performance difference between 9.5, 9.6 and 10? in > other words are there specific improvements in this area that may not > be available in all Postgres versions?>
Unlogged tables are not stored in the catalog like a regular table. When it is converted to a logged table , the entire operation is logged (goes into wal logs) in one single transaction, blocking the entire table during the process. IMO this makes unlogged -> logged workflow not a right fit for large tables. In other products I have used, large tables are set to unlogged mode before bulk load and then set back to normal logged mode.
