Lonely Rogue (9/16/2014)
and what happens with INSERT & DELETE?
The same.
further, isn't it an unnecessary effort to write back the unmodified rows too.. I wonder.
Hmm... What's more effort...
Write 8kb of data to disk at a standard offset in the file?
or
figure out what part of the of the page the changed row is on, write the row (a variable amount of data at a not standard offset in the file)
then figure out what portion of the page header has changed, write that (a variable amount of data at a not standard offset in the file)
then figure out what portion of the page footer has changed, write that (a variable amount of data at a not standard offset in the file)
and then hope and pray that all three writes succeeded otherwise it's a guaranteed corrupt page and data loss?
And that's not even touching compressed pages...
Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability