Remove WritableFile(FSWritableFile)::GetFileSize default implementation (#12303)

Summary:
As titled. This changes public API behavior, and subclasses of `WritableFile` and `FSWritableFile` need to explicitly provide an implementation for the `GetFileSize` method after this change.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/12303

Reviewed By: ajkr

Differential Revision: D53205769

Pulled By: jowlyzhang

fbshipit-source-id: 2e613ca3650302913821b33159b742bdf1d24bc7

include/rocksdb/env.h

@@ -1002,7 +1002,7 @@ class WritableFile {
   /*
    * Get the size of valid data in the file.
    */
-  virtual uint64_t GetFileSize() { return 0; }
+  virtual uint64_t GetFileSize() = 0;
 
   /*
    * Get and set the default pre-allocation block size for writes to

include/rocksdb/file_system.h

@@ -1144,9 +1144,7 @@ class FSWritableFile {
    * Get the size of valid data in the file.
    */
   virtual uint64_t GetFileSize(const IOOptions& /*options*/,
-                               IODebugContext* /*dbg*/) {
-    return 0;
-  }
+                               IODebugContext* /*dbg*/) = 0;
 
   /*
    * Get and set the default pre-allocation block size for writes to

test_util/testutil.h

@@ -189,6 +189,11 @@ class StringSink : public FSWritableFile {
     }
   }
 
+  uint64_t GetFileSize(const IOOptions& /*options*/,
+                       IODebugContext* /*dbg*/) override {
+    return contents_.size();
+  }
+
  private:
   Slice* reader_contents_;
   size_t last_flush_;
@@ -285,6 +290,11 @@ class OverwritingStringSink : public FSWritableFile {
     if (last_flush_ > contents_.size()) last_flush_ = contents_.size();
   }
 
+  uint64_t GetFileSize(const IOOptions& /*options*/,
+                       IODebugContext* /*dbg*/) override {
+    return contents_.size();
+  }
+
  private:
   std::string contents_;
   Slice* reader_contents_;
@@ -562,6 +572,14 @@ class StringFS : public FileSystemWrapper {
       return IOStatus::OK();
     }
 
+    uint64_t GetFileSize(const IOOptions& /*options*/,
+                         IODebugContext* /*dbg*/) override {
+      if (contents_ != nullptr) {
+        return contents_->size();
+      }
+      return 0;
+    }
+
    private:
     std::string* contents_;
   };

unreleased_history/public_api_changes/remove_default_get_file_size.md

@@ -0,0 +1 @@
+*Remove the default `WritableFile::GetFileSize` and `FSWritableFile::GetFileSize` implementation that returns 0 and make it pure virtual, so that subclasses are enforced to explicitly provide an implementation.

util/file_reader_writer_test.cc

@@ -463,6 +463,11 @@ TEST_F(WritableFileWriterTest, AppendStatusReturn) {
     void Setuse_direct_io(bool val) { use_direct_io_ = val; }
     void SetIOError(bool val) { io_error_ = val; }
 
+    uint64_t GetFileSize(const IOOptions& /*options*/,
+                         IODebugContext* /*dbg*/) override {
+      return 0;
+    }
+
    protected:
     bool use_direct_io_;
     bool io_error_;
@@ -862,6 +867,11 @@ TEST_F(DBWritableFileWriterTest, IOErrorNotification) {
       ASSERT_EQ(file_flush_errors_, file_flush_errors);
     }
 
+    uint64_t GetFileSize(const IOOptions& /*options*/,
+                         IODebugContext* /*dbg*/) override {
+      return 0;
+    }
+
    protected:
     bool io_error_;
     std::atomic<size_t> file_append_errors_;

utilities/fault_injection_fs.h

@@ -96,6 +96,11 @@ class TestFSWritableFile : public FSWritableFile {
     return target_->use_direct_io();
   }
 
+  virtual uint64_t GetFileSize(const IOOptions& options,
+                               IODebugContext* dbg) override {
+    return target_->GetFileSize(options, dbg);
+  }
+
  private:
   FSFileState state_;  // Need protection by mutex_
   FileOptions file_opts_;