From fd0e99e618319974320ed3fb49535aec501be1fb Mon Sep 17 00:00:00 2001
From: Douglas Rumbaugh <dbr4@psu.edu>
Date: Thu, 6 Feb 2025 15:56:33 -0500
Subject: Background compaction stuff

---
 include/framework/scheduling/Task.h    |  1 +
 include/framework/scheduling/Version.h | 40 +++++++++++++++++++++++++++++-----
 2 files changed, 35 insertions(+), 6 deletions(-)

(limited to 'include/framework/scheduling')

diff --git a/include/framework/scheduling/Task.h b/include/framework/scheduling/Task.h
index 1591909..ed40d3d 100644
--- a/include/framework/scheduling/Task.h
+++ b/include/framework/scheduling/Task.h
@@ -36,6 +36,7 @@ struct ReconstructionArgs {
   ReconstructionVector tasks;
   void *extension;
   ReconstructionPriority priority;
+  size_t initial_version;
 };
 
 template <ShardInterface S, QueryInterface<S> Q, typename DE> struct QueryArgs {
diff --git a/include/framework/scheduling/Version.h b/include/framework/scheduling/Version.h
index 3e93202..fa677f2 100644
--- a/include/framework/scheduling/Version.h
+++ b/include/framework/scheduling/Version.h
@@ -89,16 +89,44 @@ public:
     return m_buffer->advance_head(new_head);
   }
 
+  void merge_changes_from(Version *old, size_t version_id) {
+    /*
+     * for a maint reconstruction, the buffer head may have advanced
+     * during the reconstruction; we don't need to adjust the buffer
+     * for maintenance reconstructions, so we can simply "catch" the
+     * internal head index up to the current version.
+     */
+    if (old->m_buffer_head > m_buffer_head) {
+      m_buffer_head = old->m_buffer_head;
+    }
+
+    // FIXME: we should also ensure that we don't clobber anything
+    // in the event that multiple concurrent reconstructions affect
+    // the same levels. As it stands, two reconstructions *could* share
+    // source shards, resulting in some records being lost or duplicated.
+    // 
+    // For the moment, I'm being careful to avoid this within the
+    // scheduling policy itself, and only forwarding changes to this
+    // version.
+
+    /* using INVALID_VERSION disables shard reconcilliation */
+    if (version_id == 0) {
+      return;
+    }
+
+    /* add any shards newer than version_id to this version */
+    auto old_structure = old->get_structure();
+    m_structure->merge_structure(old_structure, version_id);
+  }
+
+  void update_shard_version(size_t version) {
+    m_structure->update_shard_version(version);
+  }
+
 private:
   BufferType *m_buffer;
   std::unique_ptr<StructureType> m_structure;
 
-  /*
-   * The number of currently active jobs
-   * (queries/merges) operating on this
-   * epoch. An epoch can only be retired
-   * when this number is 0.
-   */
   size_t m_id;
   size_t m_buffer_head;
   ssize_t m_pending_buffer_head;
-- 
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