On Wed, Oct 27, 2010 at 2:14 PM, Divakar Singh <dpsmails@xxxxxxxxx> wrote: > yes this is a very clearly visible problem. > The difference b/w oracle and PG increases with more rows. > when oracle takes 3 GB, PG takes around 6 GB. > I only use varchar. > I will try to use your tips on "smart table layout, toast compression". > Assuming these suggested options do not have any performance penalty? These will only be helpful in particular cases, for example if your layout is bad :-). toast compression is for dealing with large datums (on by default iirc). Also it's very hard to get apples to apples comparison test via synthetic insertion benchmark. It's simply not the whole story. The deal with postgres is that things are pretty optimized and fairly unlikely to get a whole lot better than they are today. The table layout is pretty optimal already, nulls are bitmaps, data lengths are using fancy bitwise length mechanism, etc. Each record in postgres has a 20 byte header that has to be factored in to any storage estimation, plus the index usage. Postgres indexes are pretty compact, and oracle (internals I am not familiar with) also has to do MVCC type management, so I am suspecting your measurement is off (aka, operator error) or oracle is cheating somehow by optimizing away storage requirements somehow via some sort of tradeoff. However you still fail to explain why storage size is a problem. Are planning to port oracle to postgres on a volume that is >50% full? :-) merlin -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
