Remove Compaction::ReleaseInputs().

Summary:
This patch remove the unnecessary Compaction::ReleaseInputs().

Compaction::ReleaseInputs() tries to unref its input_version
and column_family.  However, such unref is always done in
~Compaction(), and all current ReleaseInputs() calls are
right before the destructor.

Test Plan: ./db_test

Reviewers: igor

Reviewed By: igor

Subscribers: igor, rven, dhruba, sdong

Differential Revision: https://reviews.facebook.net/D31605

db/compaction.cc

@@ -242,19 +242,6 @@ void Compaction::SetupBottomMostLevel(VersionStorageInfo* vstorage,
   }
 }
 
-void Compaction::ReleaseInputs() {
-  if (input_version_ != nullptr) {
-    input_version_->Unref();
-    input_version_ = nullptr;
-  }
-  if (cfd_ != nullptr) {
-    if (cfd_->Unref()) {
-      delete cfd_;
-    }
-    cfd_ = nullptr;
-  }
-}
-
 void Compaction::ReleaseCompactionFiles(Status status) {
   cfd_->compaction_picker()->ReleaseCompactionFiles(this, status);
 }

db/compaction.h

@@ -135,10 +135,6 @@ class Compaction {
   // before processing "internal_key".
   bool ShouldStopBefore(const Slice& internal_key);
 
-  // Release the input version for the compaction, once the compaction
-  // is successful.
-  void ReleaseInputs();
-
   // Clear all files to indicate that they are not being compacted
   // Delete this compaction from the list of running compactions.
   void ReleaseCompactionFiles(Status status);

db/db_impl.cc

@@ -1344,7 +1344,6 @@ Status DBImpl::CompactFilesImpl(
                                   *c->mutable_cf_options());
   }
   c->ReleaseCompactionFiles(s);
-  c->ReleaseInputs();
   c.reset();
 
   if (status.ok()) {
@@ -2203,9 +2202,9 @@ Status DBImpl::BackgroundCompaction(bool* madeProgress, JobContext* job_context,
                                     *c->mutable_cf_options());
     }
     c->ReleaseCompactionFiles(status);
-    c->ReleaseInputs();
     *madeProgress = true;
   }
+  // this will unref its input_version and column_family_data
   c.reset();
 
   if (status.ok()) {