高健 escribió: > ... > Checkpoints are fairly expensive, first because they require writing out > all currently dirty buffers, and second because they result in extra > subsequent WAL traffic as discussed above. > ... > > What confused me is that: (checkpoint)result in extra subsequent WAL > traffic as discussed above... > > I haven't found any more information can describe it in the "above" of that > page.
It means that the first change following the checkpoint that affects any particular page will require a full page image of that page to be written to WAL. See the discussion in the preceding paragraph about "full_page_writes". It's not the checkpoint itself that writes this extra WAL, but the rest of the system. -- Álvaro Herrera http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services -- Sent via pgsql-general mailing list (pgsql-general@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
