add gc logic

Author: Dean Chen

src/catalog/catalog.cpp

@@ -1099,8 +1099,8 @@ ResultType Catalog::AlterTable(oid_t database_oid, oid_t table_oid, const std::s
             txn);
         column_offset++;
       }
-      // TODO: Add gc logic
-      // txn->RecordDrop(database_oid, old_table->GetOid(), INVALID_OID);
+      // Garbage collection
+      txn->RecordDropTable(old_table);
 
       // Final step of physical change should be moved to commit time
       database->ReplaceTableWithOid(table_oid, new_table);

src/gc/transaction_level_gc_manager.cpp

@@ -278,6 +278,11 @@ void TransactionLevelGCManager::AddToRecycleMap(
     LOG_DEBUG("GCing index %u", index_oid);
   }
 
+  for (auto table : txn_ctx->GetDroppedTables()) {
+    LOG_TRACE("deleting table when txn commits");
+    delete table;
+  }
+
   delete txn_ctx;
 }
 

src/include/concurrency/transaction_context.h

@@ -33,6 +33,10 @@ class TriggerSet;
 class TriggerData;
 }  // namespace trigger
 
+namespace storage {
+class DataTable;
+}
+
 namespace concurrency {
 
 //===--------------------------------------------------------------------===//
@@ -173,6 +177,14 @@ class TransactionContext : public Printable {
 
   void RecordInsert(const ItemPointer &);
 
+  void RecordDropTable(storage::DataTable *table) {
+    dropped_tables.push_back(table);
+  }
+
+  std::vector<storage::DataTable *> &GetDroppedTables() {
+    return dropped_tables;
+  }
+
   /**
    * @brief      Delete the record.
    *
@@ -341,6 +353,9 @@ class TransactionContext : public Printable {
   IsolationLevelType isolation_level_;
 
   std::unique_ptr<trigger::TriggerSet> on_commit_triggers_;
+
+  /** vector of dropped data tables **/
+  std::vector<storage::DataTable *> dropped_tables;
 };
 
 }  // namespace concurrency