On Tue, Jun 23, 2020 at 11:53 PM David Rowley <dgrowle...@gmail.com> wrote: > In summary, based on these tests, I don't think we're making anything > worse in regards to synchronize_seqscans if we cap the maximum number > of blocks to allocate to each worker at once to 8192. Perhaps there's > some argument for using something smaller than that for servers with > very little RAM, but I don't personally think so as it still depends > on the table size and It's hard to imagine tables in the hundreds of > GBs on servers that struggle with chunk allocations of 16MB. The > table needs to be at least ~70GB to get a 8192 chunk size with the > current v2 patch settings.
Nice research. That makes me happy. I had a feeling the maximum useful chunk size ought to be more in this range than the larger values we were discussing before, but I didn't even think about the effect on synchronized scans. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company
