On Fri, Jun 7, 2024 at 4:36 AM Sam Kidman <sam@fresho.com> wrote:
> This is due to the way that RDS restores snapshots.
Thanks, I never would have guessed. Would vacuum analyze be sufficient to defeat the lazy loading or would we need to do something more specific to our application? (for example. select(*) on some commonly used tables)
pg_prewarm is probably what you want. Don't know if RDS Postgresql supports it or not, though.
I think vacuum full would certainly defeat the lazy loading since it would copy all of the table data, but that may take a very long time to run. I think vacuum analyze only scans a subset of rows but I might be wrong about that.
Best, Sam
On Wed, Jun 5, 2024 at 10:09 PM Jeremy Smith <jeremy@musicsmith.net> wrote: > > On Wed, Jun 5, 2024 at 4:23 AM Sam Kidman <sam@fresho.com> wrote: > > > We get very poor performance in the staging environment after this > > restore takes place - after some usage it seems to get better perhaps > > because of caching. > > > > This is due to the way that RDS restores snapshots. > > From the docs (https://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/USER_RestoreFromSnapshot.html): > > You can use the restored DB instance as soon as its status is > available. The DB instance continues to load data in the background. > This is known as lazy loading. > > If you access data that hasn't been loaded yet, the DB instance > immediately downloads the requested data from Amazon S3, and then > continues loading the rest of the data in the background. > > > > -Jeremy
