Re: BUG #18170: Unexpected error: no relation entry for relid 3

Vik Fearing <vik@postgresfriends.org> writes:
> On 10/26/23 16:01, PG Bug reporting form wrote:
>> My fuzzer finds a bug in Postgres, which triggers an unexpected error.

> This bisects to d3d55ce571369dad6e1d582f1655e5a3fbd8594a, Remove useless
> self-joins.

I wonder if that new code thinks it can remove ref_2 from the query,
even though ref_2 is used in the targetlist.  I'm not seeing
control reach remove_leftjoinrel_from_query, though.

Also, while nosing around in this, I tried to pprint(root) at the
point of the error, and got

2023-10-26 12:48:37.852 EDT [1186007] WARNING:  could not dump unrecognized node type: 37413808

This happens because the patch changed RelOptInfo.unique_for_rels from
a list of Bitmapsets into a list of UniqueRelInfo, even though it did
not bother to make UniqueRelInfo be a Node type (much less document
the change in globally-visible data structures: pathnodes.h still says
it's a list of Relid sets).  This is not acceptable.

I'm getting the distinct impression that this patch wasn't
ready for prime time.

            regards, tom lane