Re: Buglist

Tom Lane wrote:
> Jan Wieck <JanWieck@Yahoo.com> writes:
> 
>>What about a little hint to the buffer management that if it has to 
>>evict another buffer to physically read this one (meaning the buffer 
>>pool was full already) then it will not put this buffer at the top of 
>>the LRU chain but rather at it's end? This way a vacuum on a large table 
>>will not cause a complete cache eviction.
> 
> 
> I think what we really need is a way to schedule VACUUM's I/O at a lower
> priority than normal I/Os.  Wouldn't be very portable :-( ... but if the
> OS offers a facility for requesting this, it'd be worth experimenting
> with.

Whatever priority it has, I think the fact that a VACUUM is kicking 
everything out of a carefully populated buffer cache and possibly 
replacing it with data of low to no interest at all should have some 
space for improvement. And that one single optimizer mistake choosing a 
seqscan over an index scan for a huge table does the same doesn't strike 
me as smart either.


Jan

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