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src/Common/FileCache.h

@@ -22,9 +22,8 @@
 namespace DB
 {
 
-/**
- * Local cache for remote filesystem files, represented as a set of non-overlapping non-empty file segments.
- */
+/// Local cache for remote filesystem files, represented as a set of non-overlapping non-empty file segments.
+/// Different caching algorithms are implemented based on IFileCachePriority.
 class FileCache : private boost::noncopyable
 {
  friend class FileSegment;

src/Common/IFileCachePriority.h

@@ -61,6 +61,7 @@ class IFileCachePriority
 
  virtual size_t hits() const = 0;
 
+ /// Point the iterator to the next higher priority cache record.
  virtual void next() const = 0;
 
  virtual bool valid() const = 0;
@@ -72,6 +73,8 @@ class IFileCachePriority
  /// Deletes an existing cached record.
  virtual void remove(std::lock_guard<std::mutex> &) = 0;
 
+ /// Get an iterator to handle write operations. Write iterators should only
+ /// be allowed to call remove, use and incrementSize methods.
  virtual WriteIterator getWriteIterator() const = 0;
 
  virtual void incrementSize(size_t, std::lock_guard<std::mutex> &) = 0;

src/Common/LRUFileCachePriority.h

@@ -5,8 +5,8 @@
 namespace DB
 {
 
-/// Based on the LRU algorithm implementation, the data with the lowest priority is stored at
-/// the head of the queue, and the data with the highest priority is stored at the tail.
+/// Based on the LRU algorithm implementation, the record with the lowest priority is stored at
+/// the head of the queue, and the record with the highest priority is stored at the tail.
 class LRUFileCachePriority : public IFileCachePriority
 {
 public: