Fix not fill values to output_exprs in agg pushdown

src/storage/access/ob_aggregated_store.cpp

@@ -152,12 +152,12 @@ int ObAggRow::init(const ObTableAccessParam &param, const int64_t batch_size)
     for (int64_t i = 0; OB_SUCC(ret) && i < param.output_exprs_->count(); ++i) {
       // mysql compatibility, select a,count(a), output the first value of a
       // from 4.3, this non-standard scalar group by will not pushdown to storage
-      // so just ignore the output_exprs_
+      // so we can just set an determined value to output_exprs_ as it's never be used
       if (T_PSEUDO_GROUP_ID == param.output_exprs_->at(i)->type_) {
         ret = OB_INVALID_ARGUMENT;
         LOG_WARN("Unexpected group idx expr", K(ret));
-      } /* else if (nullptr == param.output_sel_mask_ || param.output_sel_mask_->at(i)) {
+      } else if (nullptr == param.output_sel_mask_ || param.output_sel_mask_->at(i)) {
-        need_access_data_ = true;
+        ObAggCell *cell = nullptr;
         int32_t col_offset = param.iter_param_.out_cols_project_->at(i);
         int32_t col_index = param.iter_param_.read_info_->get_columns_index().at(col_offset);
         const share::schema::ObColumnParam *col_param = out_cols_param->at(col_offset);
@@ -165,8 +165,14 @@ int ObAggRow::init(const ObTableAccessParam &param, const int64_t batch_size)
         ObAggCellBasicInfo basic_info(col_offset, col_index, col_param, expr, batch_size);
         if (OB_FAIL(agg_cell_factory_.alloc_cell(basic_info, agg_cells_))) {
           LOG_WARN("Failed to alloc agg cell", K(ret), K(i));
+        } else if (FALSE_IT(cell = agg_cells_.at(agg_cells_.count() - 1))) {
+        } else if (OB_UNLIKELY(PD_FIRST_ROW != cell->get_type())) {
+          ret = OB_ERR_UNEXPECTED;
+          LOG_WARN("Unexpected agg type", K(ret), KPC(cell));
+        } else {
+          static_cast<ObFirstRowAggCell*>(cell)->set_determined_value();
         }
-      } */
+      }
     }
     if (OB_SUCC(ret)) {
       has_lob_column_out_ = false;

src/storage/access/ob_pushdown_aggregate.cpp

@@ -2375,6 +2375,7 @@ int ObSumAggCell::collect_result_to_decimal_int(
 
 ObFirstRowAggCell::ObFirstRowAggCell(const ObAggCellBasicInfo &basic_info, common::ObIAllocator &allocator)
     : ObAggCell(basic_info, allocator),
+      is_determined_value_(false),
       aggregated_flag_cnt_(0),
       aggregated_flag_buf_(),
       datum_allocator_("ObStorageAgg", OB_MALLOC_NORMAL_BLOCK_SIZE, MTL_ID())
@@ -2384,6 +2385,7 @@ ObFirstRowAggCell::ObFirstRowAggCell(const ObAggCellBasicInfo &basic_info, commo
 
 void ObFirstRowAggCell::reset()
 {
+  is_determined_value_ = false;
   aggregated_flag_cnt_ = 0;
   free_group_by_buf(allocator_, aggregated_flag_buf_);
   if (nullptr != agg_datum_buf_) {
@@ -2400,6 +2402,9 @@ void ObFirstRowAggCell::reuse()
   ObAggCell::reuse();
   aggregated_flag_cnt_ = 0;
   datum_allocator_.reuse();
+  if (is_determined_value_) {
+    set_determined_value();
+  }
 }
 
 void ObFirstRowAggCell::clear_group_by_info()

src/storage/access/ob_pushdown_aggregate.h

@@ -556,8 +556,17 @@ public:
   virtual bool finished() const override { return aggregated_; }
   virtual int reserve_group_by_buf(const int64_t size) override;
   virtual int output_extra_group_by_result(const int64_t start, const int64_t count) override;
+  OB_INLINE void set_determined_value()
+  {
+    is_determined_value_ = true;
+    result_datum_.reuse();
+    result_datum_.set_null();
+    aggregated_ = true;
+  }
+  INHERIT_TO_STRING_KV("ObAggCell", ObAggCell, K_(is_determined_value), K_(aggregated_flag_cnt));
 private:
   void clear_group_by_info();
+  bool is_determined_value_;
   int64_t aggregated_flag_cnt_;
   ObGroupByExtendableBuf<bool> *aggregated_flag_buf_;
   common::ObArenaAllocator datum_allocator_;

src/storage/column_store/ob_co_sstable_row_scanner.cpp

@@ -493,13 +493,10 @@ int ObCOSSTableRowScanner::construct_cg_agg_iter_params(
     }
     for (int64_t i = 0; OB_SUCC(ret) && i < access_col_cnt; ++i) {
       exprs.reuse();
-      // mysql compatibility, select a,count(a), output the first value of a
+      if (nullptr != row_param.output_sel_mask_ && !row_param.output_sel_mask_->at(i)) {
-      // from 4.3, this non-standard scalar group by will not pushdown to storage
+      } else if (OB_FAIL(exprs.push_back(row_param.output_exprs_->at(i)))) {
-      // so just ignore the output_exprs_
+        LOG_WARN("Fail to push back", K(ret), K(i));
-      // if (nullptr != row_param.output_sel_mask_ && !row_param.output_sel_mask_->at(i)) {
+      }
-      // } else if (OB_FAIL(exprs.push_back(row_param.output_exprs_->at(i)))) {
-      //   LOG_WARN("Fail to push back", K(ret), K(i));
-      // }
       const int32_t out_col_offset = row_param.out_cols_project_->at(i);
       const uint32_t cg_idx = access_cgs->at(out_col_offset);
       for (int64_t j = 0; OB_SUCC(ret) && j < row_param.agg_cols_project_->count(); ++j) {