Size of the NULL bitmap

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.

Can anyone confirm / deny?

asked Apr 21 '11 at 02:04 AM in Default

Matt Whitfield ♦♦
29.2k ● 56 ● 63 ● 87

I'm sure Klaus covered this in his talk at SQLBits... but I can't remember

Apr 21 '11 at 02:20 AM ThomasRushton ♦

(comments are locked)

1 answer:

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

answered Apr 21 '11 at 02:47 AM

Pavel Pawlowski
20.3k ● 5 ● 10 ● 20

Awesome, cheers - was clearly having an information finding fail day :)

Apr 21 '11 at 05:12 AM Matt Whitfield ♦♦

(comments are locked)

Your answer

Follow this question

By Email:

Once you sign in you will be able to subscribe for any updates here

By RSS:

Answers

Answers and Comments

Follow @Ask_SSC

Follow Ask SSC on Facebook

Find Ask SSC on Google+

Find us on LinkedIn

Topics:

storage x24
size x12

asked: Apr 21 '11 at 02:04 AM

Seen: 762 times

Last Updated: Apr 21 '11 at 02:04 AM

Size of the NULL bitmap

Follow this question

Related Questions