Reduce spurious Hot Standby conflicts from never-visible records.

Hot Standby conflicts only with tuples that were visible at
some point. So ignore tuples from aborted transactions or for
tuples updated/deleted during the inserting transaction when
generating the conflict transaction ids.

Following detailed analysis and test case by Noah Misch.
Original report covered btree delete records, correctly observed
by Heikki Linnakangas that this applies to other cases also.
Fix covers all sources of cleanup records via common code.
Includes additional fix compared to commit on HEAD

diff --git a/src/backend/access/heap/heapam.c b/src/backend/access/heap/heapam.c
index 48a387e2ecbb313803e8e5f864d26227dfc8c068..1c934007b2edbe97e548a7e84fe5802b6b8c5c98 100644 (file)
--- a/src/backend/access/heap/heapam.c
+++ b/src/backend/access/heap/heapam.c
@@ -3776,8 +3776,11 @@ heap_restrpos(HeapScanDesc scan)
 }
 
 /*
- * If 'tuple' contains any XID greater than latestRemovedXid, update
- * latestRemovedXid to the greatest one found.
+ * If 'tuple' contains any visible XID greater than latestRemovedXid,
+ * ratchet forwards latestRemovedXid to the greatest one found.
+ * This is used as the basis for generating Hot Standby conflicts, so
+ * if a tuple was never visible then removing it should not conflict
+ * with queries.
  */
 void
 HeapTupleHeaderAdvanceLatestRemovedXid(HeapTupleHeader tuple,
@@ -3793,13 +3796,25 @@ HeapTupleHeaderAdvanceLatestRemovedXid(HeapTupleHeader tuple,
                        *latestRemovedXid = xvac;
        }
 
-       if (TransactionIdPrecedes(*latestRemovedXid, xmax))
-               *latestRemovedXid = xmax;
-
-       if (TransactionIdPrecedes(*latestRemovedXid, xmin))
-               *latestRemovedXid = xmin;
+       /*
+        * Ignore tuples inserted by an aborted transaction or
+        * if the tuple was updated/deleted by the inserting transaction.
+        *
+        * Look for a committed hint bit, or if no xmin bit is set, check clog.
+        * This needs to work on both master and standby, where it is used
+        * to assess btree delete records.
+        */
+       if ((tuple->t_infomask & HEAP_XMIN_COMMITTED) ||
+               (!(tuple->t_infomask & HEAP_XMIN_COMMITTED) &&
+                !(tuple->t_infomask & HEAP_XMIN_INVALID) &&
+                TransactionIdDidCommit(xmin)))
+       {
+               if (xmax != xmin &&
+                       TransactionIdFollows(xmax, *latestRemovedXid))
+                               *latestRemovedXid = xmax;
+       }
 
-       Assert(TransactionIdIsValid(*latestRemovedXid));
+       /* *latestRemovedXid may still be invalid at end */
 }
 
 /*

diff --git a/src/backend/access/heap/pruneheap.c b/src/backend/access/heap/pruneheap.c
index 3332e085b8364074dd438c2a7ee6371b26e67c4f..6d72bb27659529fabcbfcfcf0ffcab25b99fc727 100644 (file)
--- a/src/backend/access/heap/pruneheap.c
+++ b/src/backend/access/heap/pruneheap.c
@@ -237,7 +237,6 @@ heap_page_prune(Relation relation, Buffer buffer, TransactionId OldestXmin,
                {
                        XLogRecPtr      recptr;
 
-                       Assert(TransactionIdIsValid(prstate.latestRemovedXid));
                        recptr = log_heap_clean(relation, buffer,
                                                                        prstate.redirected, prstate.nredirected,
                                                                        prstate.nowdead, prstate.ndead,

diff --git a/src/backend/access/nbtree/nbtxlog.c b/src/backend/access/nbtree/nbtxlog.c
index 32614834753a5f30e8c37fae56ca34c3ee4537d0..740986d9e11a4fcdc49bb24cf74ab5ea624536e9 100644 (file)
--- a/src/backend/access/nbtree/nbtxlog.c
+++ b/src/backend/access/nbtree/nbtxlog.c
@@ -580,7 +580,6 @@ btree_xlog_delete_get_latestRemovedXid(XLogRecord *record)
        BlockNumber hblkno;
        OffsetNumber hoffnum;
        TransactionId latestRemovedXid = InvalidTransactionId;
-       TransactionId htupxid = InvalidTransactionId;
        int                     i;
 
        /*
@@ -646,24 +645,16 @@ btree_xlog_delete_get_latestRemovedXid(XLogRecord *record)
                }
 
                /*
-                * If the heap item has storage, then read the header. Some LP_DEAD
-                * items may not be accessible, so we ignore them.
+                * If the heap item has storage, then read the header and use that to
+                * set latestRemovedXid.
+                *
+                * Some LP_DEAD items may not be accessible, so we ignore them.
                 */
                if (ItemIdHasStorage(hitemid))
                {
                        htuphdr = (HeapTupleHeader) PageGetItem(hpage, hitemid);
 
-                       /*
-                        * Get the heap tuple's xmin/xmax and ratchet up the
-                        * latestRemovedXid. No need to consider xvac values here.
-                        */
-                       htupxid = HeapTupleHeaderGetXmin(htuphdr);
-                       if (TransactionIdFollows(htupxid, latestRemovedXid))
-                               latestRemovedXid = htupxid;
-
-                       htupxid = HeapTupleHeaderGetXmax(htuphdr);
-                       if (TransactionIdFollows(htupxid, latestRemovedXid))
-                               latestRemovedXid = htupxid;
+                       HeapTupleHeaderAdvanceLatestRemovedXid(htuphdr, &latestRemovedXid);
                }
                else if (ItemIdIsDead(hitemid))
                {