1 files changed, 88 insertions, 0 deletions
diff --git a/include/framework/reconstruction/BackgroundTieringPolicy.h b/include/framework/reconstruction/BackgroundTieringPolicy.h
new file mode 100644
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+++ b/include/framework/reconstruction/BackgroundTieringPolicy.h
@@ -0,0 +1,88 @@
+/*
+ * include/framework/reconstruction/LevelingPolicy.h
+ *
+ * Copyright (C) 2023-2024 Douglas B. Rumbaugh <drumbaugh@psu.edu>
+ *                         Dong Xie <dongx@psu.edu>
+ *
+ * Distributed under the Modified BSD License.
+ *
+ */
+#pragma once
+#include <cmath>
+
+#include "framework/reconstruction/ReconstructionPolicy.h"
+#include "framework/scheduling/Version.h"
+#include "util/types.h"
+
+namespace de {
+template <ShardInterface ShardType, QueryInterface<ShardType> QueryType>
+class BackgroundTieringPolicy : public ReconstructionPolicy<ShardType, QueryType> {
+  typedef std::vector<std::shared_ptr<InternalLevel<ShardType, QueryType>>>
+      LevelVector;
+
+public:
+  BackgroundTieringPolicy(size_t scale_factor, size_t buffer_size)
+      : m_scale_factor(scale_factor), m_buffer_size(buffer_size) {}
+
+  ReconstructionVector get_reconstruction_tasks(
+      const Version<ShardType, QueryType> *version) const override {
+    ReconstructionVector reconstructions;
+
+    auto levels = version->get_structure()->get_level_vector();
+
+    if (levels[0]->get_shard_count() < m_scale_factor) {
+      return reconstructions;
+    }
+
+    level_index target_level = find_reconstruction_target(levels);
+    assert(target_level != -1);
+    level_index source_level = 0;
+
+    if (target_level == invalid_level_idx) {
+      /* grow */
+      target_level = levels.size();
+    }
+
+    for (level_index i = target_level; i > source_level; i--) {
+      size_t target_reccnt =
+          (i < (level_index)levels.size()) ? levels[i]->get_record_count() : 0;
+      size_t total_reccnt = levels[i - 1]->get_record_count() + target_reccnt;
+
+      std::vector<ShardID> shards;
+      for (ssize_t j=0; j<(ssize_t)levels[i-1]->get_shard_count(); j++) {
+        shards.push_back({i-1, j});
+      }
+
+      reconstructions.add_reconstruction(shards, i, total_reccnt, ReconstructionType::Compact);
+    }
+    
+    return reconstructions;
+  }
+
+  ReconstructionVector
+  get_flush_tasks(const Version<ShardType, QueryType> *version) const override {
+    ReconstructionVector reconstructions;
+
+    return reconstructions;
+  }
+
+private:
+  level_index find_reconstruction_target(LevelVector &levels) const {
+    level_index target_level = invalid_level_idx;
+
+    for (level_index i = 0; i < (level_index)levels.size(); i++) {
+      if (levels[i]->get_shard_count() + 1 <= capacity()) {
+        target_level = i;
+        break;
+      }
+    }
+
+    return target_level;
+  }
+
+  inline size_t capacity() const { return m_scale_factor; }
+
+  size_t m_scale_factor;
+  size_t m_buffer_size;
+};
+} // namespace de