Clean up CompactionProxy (#7662)

Summary:
`CompactionProxy` is currently both a concrete class used for actual `Compaction`s
and a base class that `FakeCompaction` (which is used in `compaction_iterator_test`)
is derived from. This is bad from an OO design standpoint, and also results in
`FakeCompaction` containing an (uninitialized and unused) `Compaction*` member.
The patch fixes this by making `CompactionProxy` a pure interface and introducing
a separate concrete class `RealCompaction` for non-test/non-fake compactions. It
also removes an unused parameter from the virtual method `level`.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/7662

Test Plan: `make check`

Reviewed By: riversand963

Differential Revision: D24907680

Pulled By: ltamasi

fbshipit-source-id: c100ecb1beef4b0ada35e799116c5bda71719ee7

db/compaction/compaction_iterator.cc

@@ -52,7 +52,7 @@ CompactionIterator::CompactionIterator(
           report_detailed_time, expect_valid_internal_key, range_del_agg,
           blob_file_builder, allow_data_in_errors,
           std::unique_ptr<CompactionProxy>(
-              compaction ? new CompactionProxy(compaction) : nullptr),
+              compaction ? new RealCompaction(compaction) : nullptr),
           compaction_filter, shutting_down, preserve_deletes_seqnum,
           manual_compaction_paused, info_log, full_history_ts_low) {}
 

db/compaction/compaction_iterator.h

@@ -29,34 +29,57 @@ class CompactionIterator {
   // CompactionIterator uses. Tests can override it.
   class CompactionProxy {
    public:
-    explicit CompactionProxy(const Compaction* compaction)
-        : compaction_(compaction) {}
-
     virtual ~CompactionProxy() = default;
-    virtual int level(size_t /*compaction_input_level*/ = 0) const {
-      return compaction_->level();
-    }
+
+    virtual int level() const = 0;
+
     virtual bool KeyNotExistsBeyondOutputLevel(
-        const Slice& user_key, std::vector<size_t>* level_ptrs) const {
+        const Slice& user_key, std::vector<size_t>* level_ptrs) const = 0;
+
+    virtual bool bottommost_level() const = 0;
+
+    virtual int number_levels() const = 0;
+
+    virtual Slice GetLargestUserKey() const = 0;
+
+    virtual bool allow_ingest_behind() const = 0;
+
+    virtual bool preserve_deletes() const = 0;
+  };
+
+  class RealCompaction : public CompactionProxy {
+   public:
+    explicit RealCompaction(const Compaction* compaction)
+        : compaction_(compaction) {
+      assert(compaction_);
+      assert(compaction_->immutable_cf_options());
+    }
+
+    int level() const override { return compaction_->level(); }
+
+    bool KeyNotExistsBeyondOutputLevel(
+        const Slice& user_key, std::vector<size_t>* level_ptrs) const override {
       return compaction_->KeyNotExistsBeyondOutputLevel(user_key, level_ptrs);
     }
-    virtual bool bottommost_level() const {
+
+    bool bottommost_level() const override {
       return compaction_->bottommost_level();
     }
-    virtual int number_levels() const { return compaction_->number_levels(); }
-    virtual Slice GetLargestUserKey() const {
+
+    int number_levels() const override { return compaction_->number_levels(); }
+
+    Slice GetLargestUserKey() const override {
       return compaction_->GetLargestUserKey();
     }
-    virtual bool allow_ingest_behind() const {
+
+    bool allow_ingest_behind() const override {
       return compaction_->immutable_cf_options()->allow_ingest_behind;
     }
-    virtual bool preserve_deletes() const {
+
+    bool preserve_deletes() const override {
       return compaction_->immutable_cf_options()->preserve_deletes;
     }
 
-   protected:
-    CompactionProxy() = default;
-
    private:
     const Compaction* compaction_;
   };

db/compaction/compaction_iterator_test.cc

@@ -156,19 +156,22 @@ class LoggingForwardVectorIterator : public InternalIterator {
 
 class FakeCompaction : public CompactionIterator::CompactionProxy {
  public:
-  FakeCompaction() = default;
+  int level() const override { return 0; }
 
-  int level(size_t /*compaction_input_level*/) const override { return 0; }
   bool KeyNotExistsBeyondOutputLevel(
       const Slice& /*user_key*/,
       std::vector<size_t>* /*level_ptrs*/) const override {
     return is_bottommost_level || key_not_exists_beyond_output_level;
   }
+
   bool bottommost_level() const override { return is_bottommost_level; }
+
   int number_levels() const override { return 1; }
+
   Slice GetLargestUserKey() const override {
     return "\xff\xff\xff\xff\xff\xff\xff\xff\xff";
   }
+
   bool allow_ingest_behind() const override { return is_allow_ingest_behind; }
 
   bool preserve_deletes() const override { return false; }