Re: Revert: Remove useless self-joins *and* -DREALLOCATE_BITMAPSETS make server crash, regress test fail.

I also think it seems better to do bms_copy in separate steps, not only
because this keeps consistent with the existing code in
remove_rel_from_restrictinfo, but also because we need to do
bms_del_member twice for each lefthand/righthand relid set.

Speaking of consistency, do you think it would improve the code's
readability if we rearrange the code in remove_rel_from_query so that
the modifications of the same relid set are grouped together, just like
what we do in remove_rel_from_restrictinfo?  I mean something like:

   sjinf->min_lefthand = bms_copy(sjinf->min_lefthand);
   sjinf->min_lefthand = bms_del_member(sjinf->min_lefthand, relid);
   sjinf->min_lefthand = bms_del_member(sjinf->min_lefthand, ojrelid);

   ...

Thanks
Richard