db_stress: skip snapshot check if cf is dropped

Summary:
We added a new verification that ensures a value that snapshot reads when is released is the same as when it was created. This test however fails when the cf is dropped in between. The patch skips the tests if that was the case.
Closes https://github.com/facebook/rocksdb/pull/3279

Differential Revision: D6581584

Pulled By: maysamyabandeh

fbshipit-source-id: afe37d371c0f91818d2e279b3949b810e112e8eb

tools/db_stress.cc

@@ -995,6 +995,8 @@ struct ThreadState {
     const Snapshot* snapshot;
     // The cf from which we did a Get at this stapshot
     int cf_at;
+    // The name of the cf at the the time that we did a read
+    std::string cf_at_name;
     // The key with which we did a Get at this stapshot
     std::string key;
     // The status of the Get
@@ -1338,20 +1340,25 @@ class StressTest {
  private:
   Status AssertSame(DB* db, ColumnFamilyHandle* cf,
                     ThreadState::SnapshotState& snap_state) {
+    Status s;
+    if (cf->GetName() != snap_state.cf_at_name) {
+      return s;
+    }
     ReadOptions ropt;
     ropt.snapshot = snap_state.snapshot;
     PinnableSlice exp_v(&snap_state.value);
     exp_v.PinSelf();
-    Status s;
     PinnableSlice v;
     s = db->Get(ropt, cf, snap_state.key, &v);
     if (!s.ok() && !s.IsNotFound()) {
       return s;
     }
     if (snap_state.status != s) {
-      return Status::Corruption("The snapshot gave inconsistent results: (" +
-                                snap_state.status.ToString() + ") vs. (" +
-                                s.ToString() + ")");
+      return Status::Corruption(
+          "The snapshot gave inconsistent results for key " +
+          ToString(Hash(snap_state.key.c_str(), snap_state.key.size(), 0)) +
+          " in cf " + cf->GetName() + ": (" + snap_state.status.ToString() +
+          ") vs. (" + s.ToString() + ")");
     }
     if (s.ok()) {
       if (exp_v != v) {
@@ -1880,8 +1887,9 @@ class StressTest {
         // will later read the same key before releasing the snapshot and verify
         // that the results are the same.
         auto status_at = db_->Get(ropt, column_family, key, &value_at);
-        ThreadState::SnapshotState snap_state = {snapshot, rand_column_family,
-                                                 keystr, status_at, value_at};
+        ThreadState::SnapshotState snap_state = {
+            snapshot, rand_column_family, column_family->GetName(),
+            keystr,   status_at,          value_at};
         thread->snapshot_queue.emplace(
             std::min(FLAGS_ops_per_thread - 1, i + FLAGS_snapshot_hold_ops),
             snap_state);