Track WAL in MANIFEST: minor udpates (#7282)

Summary:
The updates resolve comments left from https://github.com/facebook/rocksdb/pull/7164.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/7282

Test Plan: wal_edit_test

Reviewed By: ltamasi

Differential Revision: D23196824

Pulled By: cheng-chang

fbshipit-source-id: 797f3fef27fc72114c2be777d9eadd3429da5301

db/wal_edit.cc

@@ -126,7 +126,7 @@ Status WalSet::AddWal(const WalAddition& wal) {
       ss << "WAL " << wal.GetLogNumber() << " is created more than once";
       return Status::Corruption("WalSet", ss.str());
     }
-    wals_[wal.GetLogNumber()] = wal.GetMetadata();
+    wals_.insert(it, {wal.GetLogNumber(), wal.GetMetadata()});
   }
   return Status::OK();
 }
@@ -143,9 +143,9 @@ Status WalSet::AddWals(const WalAdditions& wals) {
 }
 
 Status WalSet::DeleteWal(const WalDeletion& wal) {
-  auto it = wals_.lower_bound(wal.GetLogNumber());
+  auto it = wals_.find(wal.GetLogNumber());
   // The WAL must exist and has been closed.
-  if (it == wals_.end() || it->first != wal.GetLogNumber()) {
+  if (it == wals_.end()) {
     std::stringstream ss;
     ss << "WAL " << wal.GetLogNumber() << " must exist before deletion";
     return Status::Corruption("WalSet", ss.str());

db/wal_edit_test.cc

@@ -109,10 +109,10 @@ TEST(WalSet, DeleteNonExistingWal) {
 }
 
 TEST(WalSet, DeleteNonClosedWal) {
-  constexpr WalNumber kNonExistingNumber = 100;
+  constexpr WalNumber kNonClosedWalNumber = 100;
   WalSet wals;
-  ASSERT_OK(wals.AddWal(WalAddition(kNonExistingNumber)));
-  Status s = wals.DeleteWal(WalDeletion(kNonExistingNumber));
+  ASSERT_OK(wals.AddWal(WalAddition(kNonClosedWalNumber)));
+  Status s = wals.DeleteWal(WalDeletion(kNonClosedWalNumber));
   ASSERT_TRUE(s.IsCorruption());
   ASSERT_TRUE(s.ToString().find("WAL 100 must be closed before deletion") !=
               std::string::npos);