On 6/1/05, Hugo Ahlenius <[EMAIL PROTECTED]> wrote: > | > Let's say you're building a data warehouse -- doubling the > | size of the > | > text columns in the fact tables (from varchar to nvarchar) to make > | > them unicode as opposed to using the correct character set makes a > > To add to Paul's informative post -- with the price of disk space today, > space shouldn't be such a big problem, and with a good RDBMS, it > shouldn't matter (as long as the indexes placed correctly).
In a data warehouse, disk space *does* become an issue. Managing 2-8TB is not all that easy. Indexes on the text field become correspondingly larger as well. The math's not all that hard -- take 8 billion rows (Cox Cable's MySQL customer database for example) and double the size of a varchar(10) by making it nvarchar(10). Add in the increased size on the index. A fair number of extra disks to buy... And while disk space is *relatively* cheap, it gets worse from there from a performance perspective -- the change will half the number of pages the database can load into memory, which in the worst case doubles the disk I/0 or requires double the memory. It halves the load speed for disk I/O since the same record is twice as long. You start adding up the performance degredation on a datawarehouse that operates on billions of rows and ironically the bytes become important. Similar things happen for MS-SQL or any database platform. Data warehouses are a different animal from OLTP systems. -- John Paul Ashenfelter CTO/Transitionpoint (blog) http://www.ashenfelter.com (email) [EMAIL PROTECTED] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~| Find out how CFTicket can increase your company's customer support efficiency by 100% http://www.houseoffusion.com/banners/view.cfm?bannerid=49 Message: http://www.houseoffusion.com/lists.cfm/link=i:4:208191 Archives: http://www.houseoffusion.com/cf_lists/threads.cfm/4 Subscription: http://www.houseoffusion.com/lists.cfm/link=s:4 Unsubscribe: http://www.houseoffusion.com/cf_lists/unsubscribe.cfm?user=89.70.4 Donations & Support: http://www.houseoffusion.com/tiny.cfm/54
