When working out the storage requirements on a per-row basis, how is the size of the NULL bitmap determined?
I know that there are CEILING(n / 8) bytes of NULL bitmap per n columns - but what I don't know is whether there are always two column count bytes or not.
CEILING(n / 8)
Can anyone confirm / deny?
Apr 21, 2011 at 02:04 AM
Matt Whitfield ♦♦
I'm sure Klaus covered this in his talk at SQLBits... but I can't remember
According the MSDN, there are the 2 bytes alwas: Null_Bitmap = 2 + ((Num_Cols + 7) / 8)
Estimating the Size of a Heap
Estimating the Size of a Clustered Index
Apr 21, 2011 at 02:47 AM
Awesome, cheers - was clearly having an information finding fail day :)
Up to 2 attachments (including images) can be used with a maximum of 524.3 kB each and 1.0 MB total.
Once you sign in you will be able to subscribe for any updates here
Answers and Comments
Need long-form SQL discussion? SQLserverCentral.com is the place.
asked: Apr 21, 2011 at 02:04 AM
Seen: 2189 times
Last Updated: Apr 21, 2011 at 02:04 AM
Does a persisted computed column need to be deterministic?
How Data is stored inside SQL Server? What order is it stored?
What counters should I baseline before moving to a SAN?
Handeling Databases larger than the 2Tb LUN Allotment.
could not allocate space but 2nd file has enough space
SQL Server cluster with shared storage
Asking for storage and SQL Server: how and what to do
LOB data on a different filegroup - performance issues/gains?
how to get top 10 tables in size in a database in a sql server ?
SQL Server to store article