Re: Use generation context to speed up tuplesorts

Hi,

On 2022-02-18 12:10:51 +1300, David Rowley wrote:
> The other way I thought to fix it was by changing the logic for when
> generation blocks are freed.  In the problem case mentioned above, the
> block being freed is the current block (which was just allocated).  I
> made some changes to adjust this behaviour so that we no longer free
> the block when the final chunk is pfree()'d. Instead, that now lingers
> and can be reused by future allocations, providing they fit inside it.

That makes sense to me, as long as we keep just one such block.


> The problem I see with this method is that there still could be some
> pathological case that causes us to end up storing just a single tuple per
> generation block.

Crazy idea: Detect the situation, and recompact. Create a new context, copy
all the tuples over, delete the old context. That could be a win even in less
adversarial situations than "a single tuple per generation block".


Greetings,

Andres Freund