1 files changed, 88 insertions, 0 deletions
diff --git a/storage/rocksdb/rocksdb/table/block_based/flush_block_policy.cc b/storage/rocksdb/rocksdb/table/block_based/flush_block_policy.cc
new file mode 100644
index 00000000..f5cb2d22
--- /dev/null
+++ b/storage/rocksdb/rocksdb/table/block_based/flush_block_policy.cc
@@ -0,0 +1,88 @@
+//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+
+#include "rocksdb/flush_block_policy.h"
+#include "rocksdb/options.h"
+#include "rocksdb/slice.h"
+#include "table/block_based/block_builder.h"
+#include "table/format.h"
+
+#include <cassert>
+
+namespace ROCKSDB_NAMESPACE {
+
+// Flush block by size
+class FlushBlockBySizePolicy : public FlushBlockPolicy {
+ public:
+  // @params block_size:           Approximate size of user data packed per
+  //                               block.
+  // @params block_size_deviation: This is used to close a block before it
+  //                               reaches the configured
+  FlushBlockBySizePolicy(const uint64_t block_size,
+                         const uint64_t block_size_deviation,
+                         const bool align,
+                         const BlockBuilder& data_block_builder)
+      : block_size_(block_size),
+        block_size_deviation_limit_(
+            ((block_size * (100 - block_size_deviation)) + 99) / 100),
+        align_(align),
+        data_block_builder_(data_block_builder) {}
+
+  bool Update(const Slice& key, const Slice& value) override {
+    // it makes no sense to flush when the data block is empty
+    if (data_block_builder_.empty()) {
+      return false;
+    }
+
+    auto curr_size = data_block_builder_.CurrentSizeEstimate();
+
+    // Do flush if one of the below two conditions is true:
+    // 1) if the current estimated size already exceeds the block size,
+    // 2) block_size_deviation is set and the estimated size after appending
+    // the kv will exceed the block size and the current size is under the
+    // the deviation.
+    return curr_size >= block_size_ || BlockAlmostFull(key, value);
+  }
+
+ private:
+  bool BlockAlmostFull(const Slice& key, const Slice& value) const {
+    if (block_size_deviation_limit_ == 0) {
+      return false;
+    }
+
+    const auto curr_size = data_block_builder_.CurrentSizeEstimate();
+    auto estimated_size_after =
+        data_block_builder_.EstimateSizeAfterKV(key, value);
+
+    if (align_) {
+      estimated_size_after += kBlockTrailerSize;
+      return estimated_size_after > block_size_;
+    }
+
+    return estimated_size_after > block_size_ &&
+           curr_size > block_size_deviation_limit_;
+  }
+
+  const uint64_t block_size_;
+  const uint64_t block_size_deviation_limit_;
+  const bool align_;
+  const BlockBuilder& data_block_builder_;
+};
+
+FlushBlockPolicy* FlushBlockBySizePolicyFactory::NewFlushBlockPolicy(
+    const BlockBasedTableOptions& table_options,
+    const BlockBuilder& data_block_builder) const {
+  return new FlushBlockBySizePolicy(
+      table_options.block_size, table_options.block_size_deviation,
+      table_options.block_align, data_block_builder);
+}
+
+FlushBlockPolicy* FlushBlockBySizePolicyFactory::NewFlushBlockPolicy(
+    const uint64_t size, const int deviation,
+    const BlockBuilder& data_block_builder) {
+  return new FlushBlockBySizePolicy(size, deviation, false, data_block_builder);
+}
+
+}  // namespace ROCKSDB_NAMESPACE