On Fri, 2009-09-18 at 10:47 +0900, Itagaki Takahiro wrote: > Simon Riggs <si...@2ndquadrant.com> wrote: > > > * compact - page selection specifically attempts to find the lowest > > numbered blocks, so that the table will naturally shrink over time. > > We cannot shrink the table if one tuple remains at the end of table > and the tuple is always HOT-updated, because we put a new tuple into > the same page where the old tuple is placed if possible. > > In addition to your intelligent FSM search modes, > do we need another algorithm to make the compaction to work better?
Perhaps we can have an additional piece of information about a table. Something like target_size, so that normal updaters that attempt HOT updates on blocks greater than target_size would know to avoid that block and to seek a new location for the row lower in the table. Perhaps such information could be reset and then sent via invalidation mechanisms. I'm thinking along the lines of a "fire alarm". An occasional mechanism by which we can inform users of the need to evacuate certain blocks. -- Simon Riggs www.2ndQuadrant.com -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
