Hitoshi Harada <umi(dot)tanuki(at)gmail(dot)com> writes:
> It looks to me like mergejoin_allowed should be initialized to false.
> If enable_mergejoin is off and jointype != JOIN_FULL then mergejoin is
> not allowed, isn't it? Sorry for noise if it's only my confusing.
No, the code is correct as-is: we need the flag to be set true by
default, because the way that the function is using it, we'll also skip
some nestloop possibilities when it's false. Note the comment for step
2.
It could be that a different name for that flag variable would be a
better idea, but neither Robert nor I could come up with a better one.
regards, tom lane