Disallow ingesting files into dropped CFs

Summary:
This PR update IngestExternalFile to return an error if we try to ingest a file into a dropped CF.

Right now if IngestExternalFile want to flush a memtable, and it's ingesting a file into a dropped CF, it will wait forever since flushing is not possible for the dropped CF
Closes https://github.com/facebook/rocksdb/pull/1657

Differential Revision: D4318657

Pulled By: IslamAbdelRahman

fbshipit-source-id: ed6ea2b

db/db_impl.cc

@@ -6491,14 +6491,23 @@ Status DBImpl::IngestExternalFile(
 
     num_running_ingest_file_++;
 
+    // We cannot ingest a file into a dropped CF
+    if (cfd->IsDropped()) {
+      status = Status::InvalidArgument(
+          "Cannot ingest an external file into a dropped CF");
+    }
+
     // Figure out if we need to flush the memtable first
+    if (status.ok()) {
       bool need_flush = false;
       status = ingestion_job.NeedsFlush(&need_flush);
+
       if (status.ok() && need_flush) {
         mutex_.Unlock();
         status = FlushMemTable(cfd, FlushOptions(), true /* writes_stopped */);
         mutex_.Lock();
       }
+    }
 
     // Run the ingestion job
     if (status.ok()) {

db/external_sst_file_test.cc

@@ -1843,6 +1843,13 @@ TEST_F(ExternalSSTFileTest, FileWithCFInfo) {
   ASSERT_OK(db_->IngestExternalFile(handles_[2], {unknown_sst}, ifo));
   // SST CF unknown
   ASSERT_OK(db_->IngestExternalFile(handles_[0], {unknown_sst}, ifo));
+
+  // Cannot ingest a file into a dropped CF
+  ASSERT_OK(db_->DropColumnFamily(handles_[1]));
+  ASSERT_NOK(db_->IngestExternalFile(handles_[1], {unknown_sst}, ifo));
+
+  // CF was not dropped, ok to Ingest
+  ASSERT_OK(db_->IngestExternalFile(handles_[2], {unknown_sst}, ifo));
 }
 
 class TestIngestExternalFileListener : public EventListener {