Thread

1. BUG #18868: /src/backend/optimizer/path/joinrels.c list_head can be NULL

   PG Bug reporting form <noreply@postgresql.org> — 2025-03-26T10:16:53Z

   The following bug has been logged on the website:
   
   Bug reference:      18868
   Logged by:          Daniel Elishakov
   Email address:      dan-eli@mail.ru
   PostgreSQL version: 17.4
   Operating system:   ubuntu 20.04
   Description:        
   
   Pointers, returned from function 'list_head' at joinrels.c:1527 and 1528,
   may be NULL and is dereferenced at joinrels.c:1550 and 1551.
   
   

2. Re: BUG #18868: /src/backend/optimizer/path/joinrels.c list_head can be NULL

   Euler Taveira <euler@eulerto.com> — 2025-03-26T14:27:43Z

   On Wed, Mar 26, 2025, at 7:16 AM, PG Bug reporting form wrote:
   > Pointers, returned from function 'list_head' at joinrels.c:1527 and 1528,
   > may be NULL and is dereferenced at joinrels.c:1550 and 1551.
   
   joinrels.c:
   
       compute_partition_bounds(root, rel1, rel2, joinrel, parent_sjinfo,
                                &parts1, &parts2);
   
       if (joinrel->partbounds_merged)
       {    
           lcr1 = list_head(parts1);
           lcr2 = list_head(parts2);
       }    
   
   Did you read compute_partition_bounds()?
   
           if (joinrel->partbounds_merged)
           {
               get_matching_part_pairs(root, joinrel, rel1, rel2,
                                       parts1, parts2);
               Assert(list_length(*parts1) == joinrel->nparts);
               Assert(list_length(*parts2) == joinrel->nparts);
           }
   
   parts1 and parts2 uses the same condition. I expect that if there is any bug
   related to pointer deference, the assert(s) should report. Do you have a test
   case that exposes this issue?
   
   
   --
   Euler Taveira
   EDB   https://www.enterprisedb.com/