From a9ee3f2f7f557adbe5448e4f4fbf71c23fe808b1 Mon Sep 17 00:00:00 2001
From: Douglas Rumbaugh <dbr4@psu.edu>
Date: Mon, 7 Apr 2025 14:37:19 -0400
Subject: Implemented the legacy policies and fixed a few bugs

---
 include/framework/reconstruction/LevelingPolicy.h | 62 +++++++++++++----------
 1 file changed, 36 insertions(+), 26 deletions(-)

(limited to 'include/framework/reconstruction/LevelingPolicy.h')

diff --git a/include/framework/reconstruction/LevelingPolicy.h b/include/framework/reconstruction/LevelingPolicy.h
index d448fee..6e20cdb 100644
--- a/include/framework/reconstruction/LevelingPolicy.h
+++ b/include/framework/reconstruction/LevelingPolicy.h
@@ -21,11 +21,13 @@ class LevelingPolicy : public ReconstructionPolicy<ShardType, QueryType> {
       LevelVector;
 
 public:
-  LevelingPolicy(size_t scale_factor, size_t buffer_size, size_t modifier=0)
-      : m_scale_factor(scale_factor), m_buffer_size(buffer_size), m_size_modifier(modifier) {}
+  LevelingPolicy(size_t scale_factor, size_t buffer_size, size_t modifier = 0)
+      : m_scale_factor(scale_factor), m_buffer_size(buffer_size),
+        m_size_modifier(modifier) {}
 
   std::vector<ReconstructionVector>
-  get_reconstruction_tasks(const Version<ShardType, QueryType> *version, LockManager &lock_mngr) const override { 
+  get_reconstruction_tasks(const Version<ShardType, QueryType> *version,
+                           LockManager &lock_mngr) const override {
     return {};
   }
 
@@ -34,15 +36,8 @@ public:
     ReconstructionVector reconstructions;
     auto levels = version->get_structure()->get_level_vector();
 
-    /*
-     * on the very first flush, the whole structure will be empty, so
-     * there isn't anything to merge into level 1 from level 0 yet.
-     */
-    if (version->get_structure()->get_record_count() == 0) {
-      return reconstructions;
-    }
-
-    level_index target_level = find_reconstruction_target(levels, version->get_structure()->get_record_count());
+    level_index target_level = find_reconstruction_target(
+        levels, version->get_structure()->get_record_count());
     assert(target_level != -1);
     level_index source_level = 0;
 
@@ -51,29 +46,43 @@ public:
       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 =
-          (i == 0) ? m_buffer_size + target_reccnt
-                   : levels[i - 1]->get_record_count() + target_reccnt;
+    /*
+     * For leveling, the only "actual" reconstruction happens at the target
+     * level. All the other reconstructions simply shift the levels down
+     * without needing to do any rebuilding.
+     */
+    size_t target_reccnt = (target_level < (level_index)levels.size())
+                               ? levels[target_level]->get_record_count()
+                               : 0;
+    size_t total_reccnt =
+        (target_level == 1)
+            ? m_buffer_size + target_reccnt
+            : levels[target_level - 1]->get_record_count() + target_reccnt;
+    auto type = (target_level >= (level_index) levels.size()) ? ReconstructionType::Append
+                                                : ReconstructionType::Merge;
+    reconstructions.add_reconstruction(target_level - 1, target_level,
+                                       total_reccnt, type);
 
-      if (total_reccnt > 0) {
-        auto type = (i >= (level_index) levels.size()) ? ReconstructionType::Append : ReconstructionType::Merge;
-        reconstructions.add_reconstruction(i - 1, i, total_reccnt, type);
-      }
+    /*
+     * For all other levels, we'll shift them down by using a single-source
+     * append.
+     */
+    for (level_index i = target_level - 1; i > source_level; i--) {
+      reconstructions.add_reconstruction(i - 1, i, 0,
+                                         ReconstructionType::Append);
     }
-
     return reconstructions;
   }
 
 private:
-  level_index find_reconstruction_target(LevelVector &levels, size_t reccnt) const {
+  level_index find_reconstruction_target(LevelVector &levels,
+                                         size_t reccnt) const {
     level_index target_level = invalid_level_idx;
     size_t incoming_records = m_buffer_size;
 
     for (level_index i = 1; i < (level_index)levels.size(); i++) {
-      if (levels[i]->get_record_count() + incoming_records < capacity(i, reccnt)) {
+      if (levels[i]->get_record_count() + incoming_records <
+          capacity(i, reccnt)) {
         target_level = i;
         break;
       }
@@ -85,7 +94,8 @@ private:
   }
 
   inline size_t capacity(level_index level, size_t reccnt) const {
-    return m_buffer_size * pow(m_scale_factor * pow(std::log(reccnt), m_size_modifier), level);
+    return m_buffer_size *
+           pow(m_scale_factor * pow(std::log(reccnt), m_size_modifier), level);
   }
 
   size_t m_scale_factor;
-- 
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