On Tue, Sep 6, 2016 at 11:13 PM, Masahiko Sawada <sawada.m...@gmail.com> wrote: > I understood, thank you. > > I've measured the performance benefit of this patch by following steps. > 1. Create very large table and set all-visible flag to all blocks. > 2. Measure the execution time of vacuum that skips to scan all heap pages. > > * 1TB Table(visibility map size is 32MB) > HEAD : 11012.274 ms (00:11.012) > Patched : 6742.481 ms (00:06.742) > > * 8TB Table(visibility map size is 64MB) > HEAD : 69886.605 ms (01:09.887) > Patched : 35562.131 ms (00:35.562) > > * 32TB Table(visibility map size is 258MB) > HEAD: 265901.096 ms (04:25.901) > Patched: 131779.082 ms (02:11.779) > > Since current HEAD could scan visibility map twice, the execution time > of Patched is approximately half of HEAD. > But when table is several hundreds gigabyte, performance benefit would > not be large.
Wow, those are surprisingly good results. Interesting. -- 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