On Thu, Jun 15, 2006 at 10:26:59AM +0530, Praveen Kumar N wrote: > I have observed that the size of data (for example size of > table in a database) stored by database system on physical storage is > more than actual datasize.It seems database is storing data in some > format.For example i have created a table with data 15MB considering each > INTEGER of 4bytes.But after loading this data into database i have > observed that database system is storing this table in 45MB memory.So can > anybody tell me what is the reason to use so much memory? Is there any > relation between actual dataset size and size of data stored on physical > storage system. Each row has storage overhead such as values that determine which transactions can see the row. If rows have only a small amount of data then the overhead is a large proportion of the storage space. If a table has indexes then there's even more overhead. For more information see the "Database Physical Storage" chapter in the documentation, in particular the "Database Page Layout" section: http://www.postgresql.org/docs/8.1/interactive/storage-page-layout.html -- Michael Fuhr
