Does anyone have experience with using postgres for data warehousing? Right, I saw one post suggestion to use mysql for a mostly read-only database ... but anyway, I think it's not a question to change the database platform for this project, at least not today ;-) Ralph Kimball seems to be some kind of guru on data warehousing, and in his books he's strongly recommending to have a date dimension - simply a table describing all dates in the system, and having attributes for what day of the week it is, month, day of the month, week number, bank holiday, anything special, etc. Well, it does make sense if adding lots of information there that cannot easily be pulled out from elsewhere - but as for now, I'm mostly only interessted in grouping turnover/profit by weeks/months/quarters/years/weekdays. It seems so much bloated to store this information, my gut feeling tells it should be better to generate them on the fly. Postgres even allows to create an index on an expression. The question is ... I'm curious about what would yield the highest performance - when choosing between: select extract(week from created), ... from some_table where ... group by extract(week from created), ... sort by extract(week from created), ... and: select date_dim.week_num, ... from some_table join date_dim ... where ... group by date_dim.week_num, ... sort by date_dim, week_num, ... The date_dim table would eventually cover ~3 years of operation, that is less than 1000 rows.
