Kevin Grittner wrote: > Ofer Israeli <oferi@xxxxxxxxxxxxxx> wrote: >> Kevin Grittner wrote: >>> Ofer Israeli <oferi@xxxxxxxxxxxxxx> wrote: >>>> Anyone have any ideas on why the empty db is giving worse results?? >>> >>> Besides the HOT updates being fast, there is the issue of having >>> space already allocated and ready for the database to use, rather >>> than needing to make calls to the OS to create and extend files >>> as space is needed. >> >> I thought about this direction as well, but on UPDATES, some of them >> will need to ask the OS for more space anyhow at least at the >> beginning of the run, additional pages will be needed. Do you expect >> that the OS level allocations are so expensive as to show an ~%40 >> increase of processing time in average? > > Gut feel, 40% does seem high for just that; but HOT updates could > easily account for that, especially since you said that the tables > are "heavily indexed". That is, as long as there are enough updates > which don't modify indexed columns. Most, if not all of our UPDATEs, involve updating an indexed column, so HOT updates are actually not performed at all :( -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
