[Melbourne-pm] An article on session storage in perl weekly newsletter

[Toby Corkindale]

On 18/02/14 15:06, Tim Connors wrote:
> On Tue, 18 Feb 2014, Toby Corkindale wrote:
>
>> On 18/02/14 14:22, Tim Connors wrote:
>> [snip]
>>> (I still don't get the point of databases.  perl storables were always
>>> good enough for me and my tens of millions of objects in galaxy simulations)
>>
>> How did you manage multiple processes simultaneously wanting access to update
>> different parts of the same file?
>>
>> How did you handle cases where you wanted a process to guarantee that either
>> all of none of its changes were stored, but never some? (Whilst still allowing
>> simultaneous access by multiple processes)
>
> Filesystem is a database, and atomic renames :P

So a file per row?
That must perform amazingly when you want to do something like this 
across a million tiny files:
SELECT SUM(x) WHERE y > z

I guess you have to open every single file in order to flock() them so 
you get an internally consistent view. How many file handles are your 
processes allowed?