Justin Blank writes:
> My idea had been that even if the custom plans average higher cost
> than the generic plan, it is still worth considering custom plans. If
> 1 time in 5, the custom plan is 10% of the cost of the generic plan,
> it doesn't matter if the average custom plan is worse, you shou
On Sat, Mar 15, 2025 at 10:42 AM Justin Blank
wrote:
> My idea had been that even if the custom plans average higher cost
> than the generic plan, it is still worth considering custom plans. If
> 1 time in 5, the custom plan is 10% of the cost of the generic plan,
> it doesn't matter if the avera
I've been looking into the way that postgres decides whether to use a
custom or generic plan. I believe I understand how, but I have
confused myself about the why.
In plancache.c, the code always executes a custom plan for the first
five iterations, and afterwards, it compares the average cost of
