On Mon, Dec 18, 2017 at 1:03 PM, Rob Nikander <rob.nikan...@gmail.com> wrote:
> Hi, > > I've got a large table from which I'd like to completely reclaim space. I > read the docs and it sounds like I can’t run `vacuum full`, because this > table is accessed constantly and can’t have downtime. Assuming that’s true, > what do you think of the following idea? Is there a better alternative? > > 1. Replace the table T with two tables T1 and T2 and a view T that is > `select * from T1 union T2`. > 2. Write only to T1, and slowly move records from T2 to T1. > 3. When T2 is empty, redefine the view T to be simply `select * from T1`. > 4. Recreate or vacuum full T2, so space is fully reclaimed. > 5. Redefine view as the union select and repeat process going other > direction from T1 to T2, as needed. > > I guess one question is whether I can do 1 and 3 (renaming tables, > redefining views) atomically without disturbing concurrent select queries. > > This is what you want: https://github.com/reorg/pg_repack This has been around for many years and is a very trusted extension (when will it be in core????). > Rob > > >
