On Tue, May 11, 2021 at 5:38 PM Bharath Rupireddy <bharath.rupireddyforpostg...@gmail.com> wrote: > > I was going through the parallel vacuum docs and code. I found below > things, please someone clarify: > > 1) I see that a term "parallel degree" is used in the docs, code > comments, error messages "parallel vacuum degree must be a > non-negative integer", "parallel vacuum degree must be between 0 and > %d". Is there any specific reason to use the term "parallel degree"? > In the docs and code comments we generally use "parallel workers". >
The parallel degree term is used here to indicate that we compute how much parallelism we can achieve based on the indexes. > 2) The error messages "parallel vacuum degree must be between 0 and > %d" and "parallel option requires a value between 0 and %d" look > inconsistent. > I think we can make them consistent. > 5) Can the parallel_workers in below condition ever be negative in > begin_parallel_vacuum? I think we can just have if (parallel_workers > == 0). > /* Can't perform vacuum in parallel */ > if (parallel_workers <= 0) Even if it can't go negative in the current code, I don't see a problem with the current code. It seems safe like this. > 6) I think, instead of saying "using integer background workers", we > can just say "using specified or lesser number of background workers". > From the docs: Perform index vacuum and index cleanup phases of VACUUM > in parallel using integer background workers > We can say "workers specified will be used during execution" > From the docs: workers specified in integer will be used during execution > The docs here refer to "PARALLEL integer" specified in specs, so not sure if the proposed text is better. -- With Regards, Amit Kapila.
