On Tue, Jun 9, 2026 at 6:31 AM Amit Langote <[email protected]> wrote:
> On Mon, Jun 8, 2026 at 5:18 PM Amit Langote <[email protected]> > wrote: > > On Sat, Jun 6, 2026 at 6:13 PM Amit Langote <[email protected]> > wrote: > > > Thanks for the detailed report and reproducers. I’ve started looking > into this. > > > > Continuing to look. Appended this to the open items list: > > > > https://wiki.postgresql.org/wiki/PostgreSQL_19_Open_Items#Open_Issues > > Thanks again, Nik, for the thorough analysis and the reproducers -- > they made all three easy to confirm and pin down. Patches attached: > 0001 for defect 1, 0002 for defects 2 and 3. > > 0001 (defect 1): check and flush before writing the row rather than > after, and add a per-entry "flushing" flag so a re-entrant add on the > same entry during a flush takes the per-row path instead of touching > the mid-flush batch. The flag is cleared in a PG_FINALLY, which also > resets batch_count, so the entry stays reusable if a flush error is > caught by a savepoint. > > 0002 (defects 2 and 3): rather than track subxact membership per row, > confine batching to the top transaction level -- in RI_FKey_check, > when GetCurrentTransactionNestLevel() > 1, use the per-row path. I > went this way because per-entry subxact tracking isn't enough (one > entry's batch can mix rows from several levels, since the cache is > keyed by constraint), and flushing at subxact boundaries doesn't work > for deferred constraints. Once the cache only ever holds top-level > rows, a subxact abort has nothing of its own to discard, so > ri_FastPathSubXactCallback goes away -- that's what fixes your defect > 2 reproducer. For defect 3, which is still reachable at the top level, > the same patch adds a cache-wide flag set while ri_FastPathEndBatch > iterates, so a re-entrant check during the scan takes the per-row path > instead of inserting into the cache being scanned. > > The per-row path still bypasses SPI, so these stay well ahead of the > pre-19 check in terms of performance. I'd like to recover batching > across subtransactions properly in v20 but didn't want to rush it now. > > On defect 3, can you check whether your reproducer still commits the > orphan with 0002 applied, or whether (like on my build) it now raises > the violation? I'd like to be sure the bucket-placement variation you > hit is actually covered. And of course any review of the patches is > welcome. > > -- > Thanks, Amit Langote > Hi Amit, Thanks for the quick fixes. I checked v1-0001 + v1-0002 against current master (e18b0cb7) with an assertion/debug build. - Both apply cleanly to master (in sequence) - Defect 1 same-FK re-entry no longer crashes; the original shape completes and leaves the expected rows - Defect 2 subtransaction-abort case now raises the FK violation instead of committing orphans - For your defect 3 question: with 0002 applied, my reproducer no longer commits the child2 orphan. It raises: ERROR: insert or update on table "child2" violates foreign key constraint "child2_fkey" DETAIL: Key (a)=(999999) is not present in table "parent". After the error, child2_orphans = 0 and child2 is empty in my run. I also ran the regression suite in that tree; foreign_key passed, and the full run reported all 245 tests passed. So v1 looks good to me for the three reported cases. Thanks! Nik
