refactor(buffer): 优化缓冲池空闲帧管理

- 将 free_list_ 从 std::list 改为 std::vector，减少内存开销
- 使用 std::iota 初始化空闲帧列表，简化构造函数
- 调整 find_victim_page 函数，使用 vector 作为空闲帧列表

Author: Lin-jingy

.gitignore

@@ -76,4 +76,6 @@ performance_testing/*.perf
 performance_testing/*.data
 performance_testing/*.folded
 
-.cunzhi-memory/
+.cunzhi-memory/
+
+make.sh

src/execution/execution_manager.cpp

@@ -218,34 +218,33 @@ void QlManager::select_from(std::unique_ptr<AbstractExecutor> executorTreeRoot,
     // Print records
     size_t num_rec = 0;
     // 执行query_plan
-    char buffer[BUFFER_LENGTH];
-    int offset = 0;
-    int size;
+    constexpr int BUFFER_SIZE = BUFFER_LENGTH;
+    char buffer[BUFFER_SIZE];
     for (executorTreeRoot->beginTuple(); !executorTreeRoot->is_end(); executorTreeRoot->nextTuple()) {
         auto Tuple = executorTreeRoot->Next();
         const auto &cols = executorTreeRoot->cols();
         std::vector<std::string_view> columns;
         columns.reserve(cols.size());
+        size_t offset = 0;
+        size_t size;
         for (auto &col : cols) {
             char *rec_buf = Tuple->data + col.offset;
             switch (col.type) {
                 case ColType::TYPE_INT:
-                    size = sprintf(buffer + offset, "%d", *(int *)rec_buf);
+                    size = snprintf(buffer + offset, BUFFER_SIZE - offset, "%d", *(int *)rec_buf);
                     columns.emplace_back(buffer + offset, size);
                     offset += size;
                     break;
                 case ColType::TYPE_FLOAT:
-                    size = sprintf(buffer + offset, "%.6f", *(float *)rec_buf);  // 更简洁的浮点表示
+                    size = snprintf(buffer + offset, BUFFER_SIZE - offset, "%.6f", *(float *)rec_buf);  // 更简洁的浮点表示
                     columns.emplace_back(buffer + offset, size);
                     offset += size;
                     break;
                 case ColType::TYPE_STRING:
-                    size_t actual_len = strnlen(rec_buf, col.len);
-                    columns.emplace_back(rec_buf, actual_len);
+                    columns.emplace_back(rec_buf, strnlen(rec_buf, col.len));
                     break;
             }
         }
-    NXT:;
         // print record into buffer
         rec_printer.print_record(columns, context);
         // print record into file

src/record_printer.h

@@ -64,7 +64,7 @@ class RecordPrinter {
             strcpy(buffer, "| ");
             if (col.size() > COL_WIDTH) {
                 memcpy(buffer + 2, col.data(), COL_WIDTH - 3);
-                strcpy(buffer, "... ");
+                strcpy(buffer + COL_WIDTH - 1, "... ");
             } else {
                 memset(buffer + 2, ' ', COL_WIDTH - col.size());
                 memcpy(buffer + 2 + COL_WIDTH - col.size(), col.data(), col.size());

src/storage/buffer_pool_instance.cpp

@@ -33,8 +33,8 @@ bool BufferPoolInstance::find_victim_page(frame_id_t* frame_id) {
     // 如果有空闲帧,直接使用
     // Caller must hold the latch_ if free_list_ access needs protection.
     if (!free_list_.empty()) {
-        *frame_id = free_list_.front();
-        free_list_.pop_front();
+        *frame_id = free_list_.back();
+        free_list_.pop_back();
         return true;
     }
 

src/storage/buffer_pool_instance.h

@@ -24,6 +24,7 @@ See the Mulan PSL v2 for more details. */
 #include "replacer/lru_replacer.h"
 #include "replacer/replacer.h"
 #include "page_guard.h"
+#include <numeric>
 
 extern DiskManager disk_manager;
 
@@ -37,17 +38,14 @@ class BufferPoolInstance {
     static constexpr size_t pool_size_ = BUFFER_POOL_SIZE / BUFFER_POOL_INSTANCE_SIZE;  // 缓冲池大小（帧数）
     Page pages_[pool_size_];                             // 缓冲池中的页面数组，连续分配
     std::unordered_map<PageId, frame_id_t> page_table_;  // 页面到帧的映射表
-    std::list<frame_id_t> free_list_;                    // 空闲帧链表
+    std::vector<frame_id_t> free_list_;                    // 空闲帧链表
     ReplacerType replacer_;                              // 页面替换策略实现
     std::mutex latch_;                                   // 并发控制锁
 
    public:
-    BufferPoolInstance() {
-        // 初始化时，所有的page都在free_list_中
-        for (size_t i = 0; i < pool_size_; ++i) {
-            free_list_.emplace_back(static_cast<frame_id_t>(i));  // static_cast转换数据类型
-        }
-        page_table_.reserve(pool_size_);  // 预留空间，避免频繁扩容
+    BufferPoolInstance(): free_list_(pool_size_){
+        std::iota(free_list_.begin(), free_list_.end(), 0);
+        page_table_.reserve(pool_size_ * 4);  // 预留空间，避免频繁扩容
     }
 
     ~BufferPoolInstance() = default;