[CF] Change flow of CreateColumnFamily

Summary:
Previously, we first wrote to the manifest and then created internal data structure.
Now, we first create internal data structure. That way, we can write out internal comparator to the manifest

Test Plan: column_family_test

Reviewers: dhruba, haobo

CC: leveldb

Differential Revision: https://reviews.facebook.net/D16425

db/db_impl.cc

@@ -3063,17 +3063,27 @@ Status DBImpl::CreateColumnFamily(const ColumnFamilyOptions& options,
   edit.AddColumnFamily(column_family_name);
   uint32_t new_id = versions_->GetColumnFamilySet()->GetNextColumnFamilyID();
   edit.SetColumnFamily(new_id);
+  auto cfd = versions_->CreateColumnFamily(options, &edit);
+  assert(cfd != nullptr);
+  edit.SetComparatorName(cfd->internal_comparator().user_comparator()->Name());
 
   Status s = versions_->LogAndApply(default_cf_handle_->cfd(), &edit, &mutex_);
   if (s.ok()) {
-    // add to internal data structures
-    auto cfd = versions_->CreateColumnFamily(options, &edit);
     *handle = new ColumnFamilyHandleImpl(cfd, this, &mutex_);
+  } else {
+    *handle = nullptr;
+    cfd->Unref();
+    delete cfd;
   }
   mutex_.Unlock();
 
-  Log(options_.info_log, "Created column family \"%s\"",
-      column_family_name.c_str());
+  if (s.ok()) {
+    Log(options_.info_log, "Created column family \"%s\" (ID %u)",
+        column_family_name.c_str(), (unsigned)cfd->GetID());
+  } else {
+    Log(options_.info_log, "Creating column family \"%s\" FAILED -- %s",
+        column_family_name.c_str(), s.ToString().c_str());
+  }
   return s;
 }
 
@@ -3083,17 +3093,19 @@ Status DBImpl::DropColumnFamily(ColumnFamilyHandle* column_family) {
   if (cfd->GetID() == 0) {
     return Status::InvalidArgument("Can't drop default column family");
   }
-  Log(options_.info_log, "Dropping column family with id %u\n", cfd->GetID());
 
   VersionEdit edit;
   edit.DropColumnFamily();
   edit.SetColumnFamily(cfd->GetID());
 
   MutexLock l(&mutex_);
+  Status s;
   if (cfd->IsDropped()) {
-    return Status::InvalidArgument("Column family already dropped!\n");
+    s = Status::InvalidArgument("Column family already dropped!\n");
+  }
+  if (s.ok()) {
+    s = versions_->LogAndApply(cfd, &edit, &mutex_);
   }
-  Status s = versions_->LogAndApply(cfd, &edit, &mutex_);
   if (s.ok()) {
     cfd->SetDropped();
     // DB is holding one reference to each column family when it's alive,
@@ -3103,6 +3115,13 @@ Status DBImpl::DropColumnFamily(ColumnFamilyHandle* column_family) {
     }
   }
 
+  if (s.ok()) {
+    Log(options_.info_log, "Dropped column family with id %u\n", cfd->GetID());
+  } else {
+    Log(options_.info_log, "Dropping column family with id %u FAILED -- %s\n",
+        cfd->GetID(), s.ToString().c_str());
+  }
+
   return s;
 }