On Mon, Dec 18, 2017 at 1:03 PM, Rob Nikander <rob.nikander@xxxxxxxxx> 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
