On 4/4/25 02:41, Tomas Vondra wrote: > On 4/4/25 01:43, Tomas Vondra wrote: >> On 4/4/25 00:57, David Rowley wrote: >>> On Thu, 3 Apr 2025 at 04:16, Tomas Vondra <tomas.von...@postgresql.org> >>> wrote: >>>> Improve accounting for memory used by shared hash tables >>> >>> I've not looked into why, but this is causing an issue in the >>> join_rel_hash during add_join_rel(). See the attached script. >>> >>> ERROR: pfree called with invalid pointer 0x60a15edc44e0 (header >>> 0x0000002000000008) >>> >> >> Thanks for the report and reproducer. I'll take a look tomorrow. >> > > I took a quick look, and I think the reason is fairly simple - the > commit allocates the header and the directory as a single chunk. And for > shared hash tables that's fine, because those have non-expandable > directory. But the patch does the same thing for non-shared hash tables > (not intentionally), which means that if we end up expanding the hash, > it fails in dir_realloc(). Because hashp->dir is not a separately > allocated chunk. > > This is clearly a bug in the patch, I should have caught this during a > review. But I'm also quite surprised none of the regression tests seems > to expand the hash table ... > > I'll think about a way to fix this tomorrow. >
I ended up reverting this. Unfortunately, the patch assumed the directory is pre-allocated and not expanding in more places. I wasn't sure how long would it take me to fix this, or how invasive the fix would be. It seems more appropriate to revert and then maybe apply a reworked patch (not going to happen for PG18). Thanks for the report, sorry for missing the issue in the first place. -- Tomas Vondra
