On Fri, Feb 24, 2017 at 8:49 AM, Amit Kapila <amit.kapil...@gmail.com> wrote: >> IIUC, I think that we need to have the number of half-dead pages in meta >> page. > > Don't you think we need to consider backward compatibility if we want > to do that?
Yeah, that would be an on-disk format break. I think this thread is pretty short on evidence that would let us make a smart decision about what to do here. I see three possibilities. The first is that this patch is a good idea whether we do something about the issue of half-dead pages or not. The second is that this patch is a good idea if we do something about the issue of half-dead pages but a bad idea if we don't. The third is that this patch is a bad idea whether or not we do anything about the issue of half-dead pages. Unfortunately, we have no evidence at all that would let us figure out which of those three things is true. The original post didn't include any relevant benchmarks or test results. Simon's reply, which suggested that the problem of half-dead pages, didn't include any benchmarks or test results. In fact, in neither place were any tests suggested, even hypothetically, which would help us decide what to do. I had a hunch when I saw this thread that it was a good idea, and Simon has a hunch that this btree page recycling thing needs to be fixed first, and he might be right. Or we might both be wrong. Or ... who knows, really? I think we need to come up with some set of tests to figure out what actually works well in practice here. Theories are a good starting point, but good vacuum behavior is really important, and a patch that changes it ought to be backed up by at least some experimental evidence. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company -- Sent via pgsql-hackers mailing list (firstname.lastname@example.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers