On 4/21/15 4:45 PM, Jim Nasby wrote:
> This comment made me wonder... has anyone considered handing the pruning
> work off to a bgworker, at least for SELECTs? That means the selects
> themselves wouldn't be burdened by the actual prune work, only in
> notifying the bgworker. While that's not going to be free, presumably
> it's a lot cheaper...
The nice thing about having foreground queries to the light cleanup is
that they can work in parallel and naturally hit the interesting parts
of the table first.
In order for a background worker to keep up with some of the workloads
that have been presented as counterexamples, you'd need multiple
background workers operating in parallel and preferring to work on
certain parts of a table. That would require a lot more sophisticated
job management than we currently have for, say, autovacuum.