> It's not in C89 but look up "alloca".
I know about alloca...
> We don't use it anywhere in postgres currently so it's kind of unlikely we
> would start now.
:-(
>> Obviously this is a bad plan if x can be a big number because you
>> might crash your stack, but suppose we know that's not an issue? It
>> seems a shame to have to do palloc/pfree in a situation like this.
>
> palloc really isn't that expensive, unless you're allocating tons of tiny
> objects or you're in a tight loop it's not worth worrying about.
Yeah... but...
It really depends on what you compare it to. It's cheap compared to
99% of the functions in the code base - perhaps so. But it's darn
expensive compared to moving the stack pointer. I have seen profiles
for PostgreSQL and other systems where memory management is a sizable
percentage of the CPU time, so it is not silly to worry about
economizing.
...Robert
