diff options
Diffstat (limited to 'src/backend/access/heap/heapam.c')
| -rw-r--r-- | src/backend/access/heap/heapam.c | 52 |
1 files changed, 47 insertions, 5 deletions
diff --git a/src/backend/access/heap/heapam.c b/src/backend/access/heap/heapam.c index 0c0f640f640..52dda41cc43 100644 --- a/src/backend/access/heap/heapam.c +++ b/src/backend/access/heap/heapam.c @@ -2074,8 +2074,7 @@ heap_hot_search_buffer(ItemPointer tid, Relation relation, Buffer buffer, * broken. */ if (TransactionIdIsValid(prev_xmax) && - !TransactionIdEquals(prev_xmax, - HeapTupleHeaderGetXmin(heapTuple->t_data))) + !HeapTupleUpdateXmaxMatchesXmin(prev_xmax, heapTuple->t_data)) break; /* @@ -2261,7 +2260,7 @@ heap_get_latest_tid(Relation relation, * tuple. Check for XMIN match. */ if (TransactionIdIsValid(priorXmax) && - !TransactionIdEquals(priorXmax, HeapTupleHeaderGetXmin(tp.t_data))) + !HeapTupleUpdateXmaxMatchesXmin(priorXmax, tp.t_data)) { UnlockReleaseBuffer(buffer); break; @@ -2293,6 +2292,50 @@ heap_get_latest_tid(Relation relation, } /* end of loop */ } +/* + * HeapTupleUpdateXmaxMatchesXmin - verify update chain xmax/xmin lineage + * + * Given the new version of a tuple after some update, verify whether the + * given Xmax (corresponding to the previous version) matches the tuple's + * Xmin, taking into account that the Xmin might have been frozen after the + * update. + */ +bool +HeapTupleUpdateXmaxMatchesXmin(TransactionId xmax, HeapTupleHeader htup) +{ + TransactionId xmin = HeapTupleHeaderGetXmin(htup); + + /* + * If the xmax of the old tuple is identical to the xmin of the new one, + * it's a match. + */ + if (TransactionIdEquals(xmax, xmin)) + return true; + + /* + * If the Xmin that was in effect prior to a freeze matches the Xmax, + * it's good too. + */ + if (HeapTupleHeaderXminFrozen(htup) && + TransactionIdEquals(HeapTupleHeaderGetRawXmin(htup), xmax)) + return true; + + /* + * When a tuple is frozen, the original Xmin is lost, but we know it's a + * committed transaction. So unless the Xmax is InvalidXid, we don't know + * for certain that there is a match, but there may be one; and we must + * return true so that a HOT chain that is half-frozen can be walked + * correctly. + * + * We no longer freeze tuples this way, but we must keep this in order to + * interpret pre-pg_upgrade pages correctly. + */ + if (TransactionIdEquals(xmin, FrozenTransactionId) && + TransactionIdIsValid(xmax)) + return true; + + return false; +} /* * UpdateXmaxHintBits - update tuple hint bits after xmax transaction ends @@ -5712,8 +5755,7 @@ l4: * end of the chain, we're done, so return success. */ if (TransactionIdIsValid(priorXmax) && - !TransactionIdEquals(HeapTupleHeaderGetXmin(mytup.t_data), - priorXmax)) + !HeapTupleUpdateXmaxMatchesXmin(priorXmax, mytup.t_data)) { result = HeapTupleMayBeUpdated; goto out_locked; |