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

Thank you for the report.  I looked at this a little bit and I think
here is what happened.  In deconstruct_distribute_oj_quals we call
distribute_quals_to_rels using the uncopied sjinfo->syn_lefthand as
outerjoin_nonnullable, which eventually becomes rinfo->outer_relids.
Later on, when we remove useless left joins, we modify
sjinfo->syn_lefthand using bms_del_member and recycle
sjinfo->syn_lefthand.  And that causes the rinfo->outer_relids becomes
invalid, and finally triggers this issue in join_clause_is_movable_to.

Maybe we want to bms_copy sjinfo->syn_lefthand first before using it as
nonnullable_rels.

--- a/src/backend/optimizer/plan/initsplan.c
+++ b/src/backend/optimizer/plan/initsplan.c
@@ -1888,7 +1888,7 @@ deconstruct_distribute_oj_quals(PlannerInfo *root,
    qualscope = bms_union(sjinfo->syn_lefthand, sjinfo->syn_righthand);
    qualscope = bms_add_member(qualscope, sjinfo->ojrelid);
    ojscope = bms_union(sjinfo->min_lefthand, sjinfo->min_righthand);
-   nonnullable_rels = sjinfo->syn_lefthand;
+   nonnullable_rels = bms_copy(sjinfo->syn_lefthand);

I will take a closer look in the afternoon.

Thanks
Richard