SERVER-34556 Iterating through indexes for a last applied timestamp transaction should use that timestamp

2 files changed, 8 insertions, 2 deletions

diff --git a/src/mongo/db/storage/recovery_unit.h b/src/mongo/db/storage/recovery_unit.h
index 66da0523094..a69d08be2ce 100644
--- a/src/mongo/db/storage/recovery_unit.h
+++ b/src/mongo/db/storage/recovery_unit.h
@@ -149,6 +149,8 @@ public:
      *  - when using ReadSource::kProvided, the timestamp provided.
      *  - when using ReadSource::kLastAppliedSnapshot, the timestamp chosen using the storage
      * engine's last applied timestamp.
+     *  - when using ReadSource::kLastApplied, the last applied timestamp at which the current
+     * storage transaction was opened, if one is open.
      *  - when using ReadSource::kMajorityCommitted, the majority committed timestamp chosen by the
      * storage engine after a transaction has been opened or after a call to
      * obtainMajorityCommittedSnapshot().
diff --git a/src/mongo/db/storage/wiredtiger/wiredtiger_recovery_unit.cpp b/src/mongo/db/storage/wiredtiger/wiredtiger_recovery_unit.cpp
index 4b8620b8524..df20c04eb92 100644
--- a/src/mongo/db/storage/wiredtiger/wiredtiger_recovery_unit.cpp
+++ b/src/mongo/db/storage/wiredtiger/wiredtiger_recovery_unit.cpp
@@ -320,6 +320,10 @@ boost::optional<Timestamp> WiredTigerRecoveryUnit::getPointInTimeReadTimestamp()
         return _readAtTimestamp;
     }
 
+    if (_timestampReadSource == ReadSource::kLastApplied && !_readAtTimestamp.isNull()) {
+        return _readAtTimestamp;
+    }
+
     if (_timestampReadSource == ReadSource::kMajorityCommitted) {
         invariant(!_majorityCommittedSnapshot.isNull());
         return _majorityCommittedSnapshot;
@@ -359,8 +363,8 @@ void WiredTigerRecoveryUnit::_txnOpen() {
         }
         case ReadSource::kLastApplied: {
             if (_sessionCache->snapshotManager().getLocalSnapshot()) {
-                _sessionCache->snapshotManager().beginTransactionOnLocalSnapshot(session,
-                                                                                 _ignorePrepared);
+                _readAtTimestamp = _sessionCache->snapshotManager().beginTransactionOnLocalSnapshot(
+                    session, _ignorePrepared);
             } else {
                 WiredTigerBeginTxnBlock(session, _ignorePrepared).done();
             }