diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 2bfe78a92a3c0c809763687b3a2079a6d62fb857..60a2b4e43898e69b3a112f2bd6ac75b2c92bc4be 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -361,6 +361,10 @@ systable_getnext(SysScanDesc sysscan) /* * systable_recheck_tuple --- recheck visibility of most-recently-fetched tuple * + * In particular, determine if this tuple would be visible to a catalog scan + * that started now. We don't handle the case of a non-MVCC scan snapshot, + * because no caller needs that yet. + * * This is useful to test whether an object was deleted while we waited to * acquire lock on it. * @@ -370,30 +374,38 @@ systable_getnext(SysScanDesc sysscan) bool systable_recheck_tuple(SysScanDesc sysscan, HeapTuple tup) { + Snapshot freshsnap; bool result; + /* + * Trust that LockBuffer() and HeapTupleSatisfiesMVCC() do not themselves + * acquire snapshots, so we need not register the snapshot. Those + * facilities are too low-level to have any business scanning tables. + */ + freshsnap = GetCatalogSnapshot(RelationGetRelid(sysscan->heap_rel)); + if (sysscan->irel) { IndexScanDesc scan = sysscan->iscan; + Assert(IsMVCCSnapshot(scan->xs_snapshot)); Assert(tup == &scan->xs_ctup); Assert(BufferIsValid(scan->xs_cbuf)); /* must hold a buffer lock to call HeapTupleSatisfiesVisibility */ LockBuffer(scan->xs_cbuf, BUFFER_LOCK_SHARE); - result = HeapTupleSatisfiesVisibility(tup, scan->xs_snapshot, - scan->xs_cbuf); + result = HeapTupleSatisfiesVisibility(tup, freshsnap, scan->xs_cbuf); LockBuffer(scan->xs_cbuf, BUFFER_LOCK_UNLOCK); } else { HeapScanDesc scan = sysscan->scan; + Assert(IsMVCCSnapshot(scan->rs_snapshot)); Assert(tup == &scan->rs_ctup); Assert(BufferIsValid(scan->rs_cbuf)); /* must hold a buffer lock to call HeapTupleSatisfiesVisibility */ LockBuffer(scan->rs_cbuf, BUFFER_LOCK_SHARE); - result = HeapTupleSatisfiesVisibility(tup, scan->rs_snapshot, - scan->rs_cbuf); + result = HeapTupleSatisfiesVisibility(tup, freshsnap, scan->rs_cbuf); LockBuffer(scan->rs_cbuf, BUFFER_LOCK_UNLOCK); } return result;