On 19/02/11 10:38, Josh Berkus wrote:
To answer the other question, what happens when the limit is exceeded is
modeled on statement timeout, i.e query is canceled and a message says
why (exceeded temp files size).
When does this happen? When you try to allocate the file, or when it
does the original tape sort estimate?
The disadvantage of the former is that the user waited for minutes in
order to have their query cancelled. The disadvantage of the latter is
that the estimate isn't remotely accurate.
Neither - it checks each write (I think this is pretty cheap - adds two
int and double + operations and a /, > operation to FileWrite). If the
check shows you've written more than the limit, you get canceled. So you
can exceed the limit by 1 buffer size.
Yeah, the disadvantage is that (like statement timeout) it is a 'bottom
of the cliff' type of protection. The advantage is there are no false
positives...
Cheers
Mark
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