Re: BUG #18885: ERROR: corrupt MVNDistinct entry - 2

On 4/14/25 16:41, Andrei Lepikhov wrote:
> On 4/12/25 00:30, Alexander Korotkov wrote:
>> When you use add_unique_group_var() which keeps varinfos unique then
>> you can no longer expect that varinfos have the same order as
>> origin_rinfos.
> Ok, here is a patch that considers this issue. Now GroupVarInfo tracks 
> source RestrictInfo. Not sure it is an ideal approach, but we don't need 
> to synchronise the restrictions and corresponding varinfos.
This is the new version of the patch.
I don't like the previous version because it was too invasive. Also, 
add_unique_group_var checks "known equal" keys. It is not applicable in 
the current case, of course, but it still seems suspicious: equality 
expressions may be applied at an upper level of the join tree, and 
equality doesn't exist at this specific place yet. Being correct in the 
case of GROUP-BY operator estimation, such conjecture may distort 
estimation in the middle of the join tree.
With the current patch, we just stay away from that doubtful code.

-- 
regards, Andrei Lepikhov