Squashed 'src/rocksdb/' content from commit 224932d

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include/rocksdb/write_batch.h

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+// Copyright (c) 2013, Facebook, Inc.  All rights reserved.
+// This source code is licensed under the BSD-style license found in the
+// LICENSE file in the root directory of this source tree. An additional grant
+// of patent rights can be found in the PATENTS file in the same directory.
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+//
+// WriteBatch holds a collection of updates to apply atomically to a DB.
+//
+// The updates are applied in the order in which they are added
+// to the WriteBatch.  For example, the value of "key" will be "v3"
+// after the following batch is written:
+//
+//    batch.Put("key", "v1");
+//    batch.Delete("key");
+//    batch.Put("key", "v2");
+//    batch.Put("key", "v3");
+//
+// Multiple threads can invoke const methods on a WriteBatch without
+// external synchronization, but if any of the threads may call a
+// non-const method, all threads accessing the same WriteBatch must use
+// external synchronization.
+
+#ifndef STORAGE_ROCKSDB_INCLUDE_WRITE_BATCH_H_
+#define STORAGE_ROCKSDB_INCLUDE_WRITE_BATCH_H_
+
+#include <string>
+#include "rocksdb/status.h"
+
+namespace rocksdb {
+
+class Slice;
+class ColumnFamilyHandle;
+struct SliceParts;
+
+class WriteBatch {
+ public:
+  explicit WriteBatch(size_t reserved_bytes = 0);
+  ~WriteBatch();
+
+  // Store the mapping "key->value" in the database.
+  void Put(ColumnFamilyHandle* column_family, const Slice& key,
+           const Slice& value);
+  void Put(const Slice& key, const Slice& value) {
+    Put(nullptr, key, value);
+  }
+
+  // Variant of Put() that gathers output like writev(2).  The key and value
+  // that will be written to the database are concatentations of arrays of
+  // slices.
+  void Put(ColumnFamilyHandle* column_family, const SliceParts& key,
+           const SliceParts& value);
+  void Put(const SliceParts& key, const SliceParts& value) {
+    Put(nullptr, key, value);
+  }
+
+  // Merge "value" with the existing value of "key" in the database.
+  // "key->merge(existing, value)"
+  void Merge(ColumnFamilyHandle* column_family, const Slice& key,
+             const Slice& value);
+  void Merge(const Slice& key, const Slice& value) {
+    Merge(nullptr, key, value);
+  }
+
+  // If the database contains a mapping for "key", erase it.  Else do nothing.
+  void Delete(ColumnFamilyHandle* column_family, const Slice& key);
+  void Delete(const Slice& key) { Delete(nullptr, key); }
+
+  // variant that takes SliceParts
+  void Delete(ColumnFamilyHandle* column_family, const SliceParts& key);
+  void Delete(const SliceParts& key) { Delete(nullptr, key); }
+
+  // Append a blob of arbitrary size to the records in this batch. The blob will
+  // be stored in the transaction log but not in any other file. In particular,
+  // it will not be persisted to the SST files. When iterating over this
+  // WriteBatch, WriteBatch::Handler::LogData will be called with the contents
+  // of the blob as it is encountered. Blobs, puts, deletes, and merges will be
+  // encountered in the same order in thich they were inserted. The blob will
+  // NOT consume sequence number(s) and will NOT increase the count of the batch
+  //
+  // Example application: add timestamps to the transaction log for use in
+  // replication.
+  void PutLogData(const Slice& blob);
+
+  // Clear all updates buffered in this batch.
+  void Clear();
+
+  // Support for iterating over the contents of a batch.
+  class Handler {
+   public:
+    virtual ~Handler();
+    // default implementation will just call Put without column family for
+    // backwards compatibility. If the column family is not default,
+    // the function is noop
+    virtual Status PutCF(uint32_t column_family_id, const Slice& key,
+                         const Slice& value) {
+      if (column_family_id == 0) {
+        // Put() historically doesn't return status. We didn't want to be
+        // backwards incompatible so we didn't change the return status
+        // (this is a public API). We do an ordinary get and return Status::OK()
+        Put(key, value);
+        return Status::OK();
+      }
+      return Status::InvalidArgument(
+          "non-default column family and PutCF not implemented");
+    }
+    virtual void Put(const Slice& key, const Slice& value);
+    // Merge and LogData are not pure virtual. Otherwise, we would break
+    // existing clients of Handler on a source code level. The default
+    // implementation of Merge simply throws a runtime exception.
+    virtual Status MergeCF(uint32_t column_family_id, const Slice& key,
+                           const Slice& value) {
+      if (column_family_id == 0) {
+        Merge(key, value);
+        return Status::OK();
+      }
+      return Status::InvalidArgument(
+          "non-default column family and MergeCF not implemented");
+    }
+    virtual void Merge(const Slice& key, const Slice& value);
+    // The default implementation of LogData does nothing.
+    virtual void LogData(const Slice& blob);
+    virtual Status DeleteCF(uint32_t column_family_id, const Slice& key) {
+      if (column_family_id == 0) {
+        Delete(key);
+        return Status::OK();
+      }
+      return Status::InvalidArgument(
+          "non-default column family and DeleteCF not implemented");
+    }
+    virtual void Delete(const Slice& key);
+    // Continue is called by WriteBatch::Iterate. If it returns false,
+    // iteration is halted. Otherwise, it continues iterating. The default
+    // implementation always returns true.
+    virtual bool Continue();
+  };
+  Status Iterate(Handler* handler) const;
+
+  // Retrieve the serialized version of this batch.
+  const std::string& Data() const { return rep_; }
+
+  // Retrieve data size of the batch.
+  size_t GetDataSize() const { return rep_.size(); }
+
+  // Returns the number of updates in the batch
+  int Count() const;
+
+  // Constructor with a serialized string object
+  explicit WriteBatch(std::string rep): rep_(rep) {}
+
+ private:
+  friend class WriteBatchInternal;
+
+  std::string rep_;  // See comment in write_batch.cc for the format of rep_
+
+  // Intentionally copyable
+};
+
+}  // namespace rocksdb
+
+#endif  // STORAGE_ROCKSDB_INCLUDE_WRITE_BATCH_H_