Re: database physical storage

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Re: database physical storage

От:
Michael Fuhr <mike@fuhr.org>
Дата:
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

database physical storage

От:
Praveen Kumar N <praveen_n@students.iiit.net>
Дата:
hai...

 	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.

thanks in anticipation

regards,
-- 
  N Praveen Kumar

 	Imagination is more important than knowledge...
                                 --Albert Einstein
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