Hi, On 20 September 2011 18:16, Simon Riggs <simon@xxxxxxxxxxxxxxx> wrote: > It would be useful to get some balanced viewpoints on this. I see you > have Alterian experience, so if you are using both it could be > valuable info. I've never heard anyone describe the downsides of > columnar datastores, presumably there are some? Inserts are slower. I haven't done proper benchmark because there is no need for thousands inserts per sec in our database. > My understanding is that columnar will work well for queries like this > > SELECT count(*) > FROM table > WHERE col1 AND col2 AND col3 > > but less well when we include the columns in the SELECT clause. Columnar store is good if: - you are selecting less than 60% of the total row size (our table has 400 cols and usual query needs 5 - 10 cols) - aggregates: count(*), avg(), ... In some cases columnar store is able to beat Postgres + High IOPS (250k+) SSD card > Would you be able to give some viewpoints and measurements on that? Check this: http://www.greenplum.com/community/forums/showthread.php?499-enable_mergejoin-and-random_page_cost&p=1553#post1553 -- Ondrej Ivanic (ondrej.ivanic@xxxxxxxxx) -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
