Re: scalability bottlenecks with (many) partitions (and more)

On 9/22/24 17:45, Tom Lane wrote:
> Tomas Vondra <tomas@vondra.me> writes:
>> I've finally pushed this, after many rounds of careful testing to ensure
>> no regressions, and polishing.
> 
> Coverity is not terribly happy with this.  "Assert(fpPtr = fpEndPtr);"
> is very clearly not doing what you presumably intended.  The others
> look like overaggressive assertion checking.  If you don't want those
> macros to assume that the argument is unsigned, you could force the
> issue, say with
> 
>  #define FAST_PATH_GROUP(index)    \
> -    (AssertMacro(((index) >= 0) && ((index) < FP_LOCK_SLOTS_PER_BACKEND)), \
> +    (AssertMacro((uint32) (index) < FP_LOCK_SLOTS_PER_BACKEND), \
>       ((index) / FP_LOCK_SLOTS_PER_GROUP))
> 

Ah, you're right. I'll fix those asserts tomorrow.

The first is clearly wrong, of course.

For the (x >= 0) asserts, doing it this way relies on negative values
wrapping to large positive ones, correct? AFAIK it's guaranteed to be a
very large value, so it can't accidentally be less than the slot count.


regards

-- 
Tomas Vondra