Limit prefetch depth in scan/multi-scan

src/storage/access/ob_index_tree_prefetcher.cpp

@@ -674,6 +674,7 @@ void ObIndexTreeMultiPassPrefetcher::reset()
   can_blockscan_ = false;
   is_prefetch_end_ = false;
   is_row_lock_checked_ = false;
+  need_check_prefetch_depth_ = false;
   cur_range_fetch_idx_ = 0;
   cur_range_prefetch_idx_ = 0;
   max_range_prefetching_cnt_ = 0;
@@ -699,6 +700,7 @@ void ObIndexTreeMultiPassPrefetcher::reuse()
   clean_blockscan_check_info();
   is_prefetch_end_ = false;
   is_row_lock_checked_ = false;
+  need_check_prefetch_depth_ = false;
   cur_range_fetch_idx_ = 0;
   cur_range_prefetch_idx_ = 0;
   cur_micro_data_fetch_idx_ = -1;
@@ -816,6 +818,12 @@ int ObIndexTreeMultiPassPrefetcher::init_basic_info(
   cur_level_ = 0;
   iter_type_ = iter_type;
   index_tree_height_ = sstable_->get_meta().get_index_tree_height();
+  need_check_prefetch_depth_ =
+      (ObStoreRowIterator::IteratorScan == iter_type || ObStoreRowIterator::IteratorMultiScan == iter_type) &&
+      iter_param_->limit_prefetch_ &&
+      nullptr != access_ctx_->limit_param_ &&
+      access_ctx_->limit_param_->limit_ >= 0 &&
+      access_ctx_->limit_param_->limit_ < 4096;
   switch (iter_type) {
     case ObStoreRowIterator::IteratorMultiGet: {
       rowkeys_ = static_cast<const common::ObIArray<blocksstable::ObDatumRowkey> *> (query_range);
@@ -982,6 +990,7 @@ int ObIndexTreeMultiPassPrefetcher::try_add_query_range(ObIndexTreeLevelHandle &
   return ret;
 }
 
+static int32_t OB_SSTABLE_MICRO_AVG_COUNT = 100;
 int ObIndexTreeMultiPassPrefetcher::prefetch_micro_data()
 {
   int ret = OB_SUCCESS;
@@ -995,7 +1004,13 @@ int ObIndexTreeMultiPassPrefetcher::prefetch_micro_data()
   } else {
     int64_t prefetched_cnt = 0;
     int64_t prefetch_micro_idx = 0;
-    prefetch_depth_ = min(max_micro_handle_cnt_, 2 * prefetch_depth_);
+    prefetch_depth_ = MIN(max_micro_handle_cnt_, 2 * prefetch_depth_);
+    if (need_check_prefetch_depth_) {
+      int64_t prefetch_micro_cnt = MAX(1,
+          (access_ctx_->limit_param_->offset_ + access_ctx_->limit_param_->limit_ - access_ctx_->out_cnt_ + \
+          OB_SSTABLE_MICRO_AVG_COUNT - 1) / OB_SSTABLE_MICRO_AVG_COUNT);
+      prefetch_depth_ = MIN(prefetch_depth_, prefetch_micro_cnt);
+    }
     int64_t prefetch_depth = min(static_cast<int64_t>(prefetch_depth_),
                                  max_micro_handle_cnt_ - (micro_data_prefetch_idx_ - cur_micro_data_fetch_idx_));
     while (OB_SUCC(ret) && prefetched_cnt < prefetch_depth) {

src/storage/access/ob_index_tree_prefetcher.h

@@ -317,6 +317,7 @@ public:
       row_lock_check_version_(transaction::ObTransVersion::INVALID_TRANS_VERSION),
       agg_row_store_(nullptr),
       can_blockscan_(false),
+      need_check_prefetch_depth_(false),
       iter_type_(0),
       cur_level_(0),
       index_tree_height_(0),
@@ -376,7 +377,8 @@ public:
                        K_(is_prefetch_end), K_(cur_range_fetch_idx), K_(cur_range_prefetch_idx), K_(max_range_prefetching_cnt),
                        K_(cur_micro_data_fetch_idx), K_(micro_data_prefetch_idx), K_(max_micro_handle_cnt),
                        K_(iter_type), K_(cur_level), K_(index_tree_height), K_(prefetch_depth),
-                       K_(total_micro_data_cnt), KP_(query_range), K_(tree_handles), K_(border_rowkey));
+                       K_(total_micro_data_cnt), KP_(query_range), K_(tree_handles), K_(border_rowkey),
+                       K_(can_blockscan), K_(need_check_prefetch_depth));
 private:
   int init_basic_info(
       const int iter_type,
@@ -566,6 +568,7 @@ public:
   ObAggregatedStore *agg_row_store_;
 private:
   bool can_blockscan_;
+  bool need_check_prefetch_depth_;
   int16_t iter_type_;
   int16_t cur_level_;
   int16_t index_tree_height_;

src/storage/access/ob_table_access_param.cpp

@@ -41,6 +41,7 @@ ObTableIterParam::ObTableIterParam()
       has_virtual_columns_(false),
       has_lob_column_out_(false),
       is_for_foreign_check_(false),
+      limit_prefetch_(false),
       ss_rowkey_prefix_cnt_(0),
       pd_storage_flag_(0)
 {
@@ -70,6 +71,7 @@ void ObTableIterParam::reset()
   has_virtual_columns_ = false;
   has_lob_column_out_ = false;
   is_for_foreign_check_ = false;
+  limit_prefetch_ = false;
 }
 
 bool ObTableIterParam::is_valid() const
@@ -136,7 +138,10 @@ DEF_TO_STRING(ObTableIterParam)
        K_(pd_storage_flag),
        K_(vectorized_enabled),
        K_(has_virtual_columns),
-       K_(has_lob_column_out));
+       K_(has_lob_column_out),
+       K_(is_for_foreign_check),
+       K_(limit_prefetch),
+       K_(ss_rowkey_prefix_cnt));
   J_OBJ_END();
   return pos;
 }
@@ -222,6 +227,7 @@ int ObTableAccessParam::init(
     iter_param_.has_virtual_columns_ = table_param.has_virtual_column();
     // vectorize requires blockscan is enabled(_pushdown_storage_level > 0)
     iter_param_.vectorized_enabled_ = nullptr != op_ && op_->is_vectorized();
+    iter_param_.limit_prefetch_ = (nullptr == op_filters_ || op_filters_->empty());
 
     if (OB_FAIL(iter_param_.check_read_info_valid())) {
       STORAGE_LOG(WARN, "Failed to check read info valdie", K(ret), K(iter_param_));

src/storage/access/ob_table_access_param.h

@@ -165,6 +165,7 @@ public:
   // so we can generate from the request cols in readinfo without considering fuse row cache
   bool has_lob_column_out_;
   bool is_for_foreign_check_;
+  bool limit_prefetch_;
   int64_t ss_rowkey_prefix_cnt_;
   union {
     struct {