YQL-20059: Remove dechunking from fallback handler

commit_hash:20bcd0062beca6963b3c420835a33b9873f43ab2

Author: MrLolthe1st

yt/yql/providers/yt/comp_nodes/dq/dq_yt_block_reader.cpp

@@ -230,48 +230,15 @@ class TBlockBuilder {
         ++RowsCnt_;
     }
 
-    std::vector<TResultBatch::TPtr> Build() {
+    TResultBatch::TPtr Build() {
         std::vector<arrow::Datum> columns;
         columns.reserve(ColumnBuilders_.size());
         for (size_t i = 0; i < ColumnBuilders_.size(); ++i) {
             columns.emplace_back(std::move(ColumnBuilders_[i]->Build(false)));
         }
-        std::vector<std::shared_ptr<TResultBatch>> blocks;
-        int64_t offset = 0;
-        std::vector<int64_t> currentChunk(columns.size()), inChunkOffset(columns.size());
-        while (RowsCnt_) {
-            int64_t max_curr_len = RowsCnt_;
-            for (size_t i = 0; i < columns.size(); ++i) {
-                if (arrow::Datum::Kind::CHUNKED_ARRAY == columns[i].kind()) {
-                    auto& c_arr = columns[i].chunked_array();
-                    while (currentChunk[i] < c_arr->num_chunks() && !c_arr->chunk(currentChunk[i])) {
-                        ++currentChunk[i];
-                    }
-                    YQL_ENSURE(currentChunk[i] < c_arr->num_chunks());
-                    max_curr_len = std::min(max_curr_len, c_arr->chunk(currentChunk[i])->length() - inChunkOffset[i]);
-                }
-            }
-            RowsCnt_ -= max_curr_len;
-            decltype(columns) result_columns;
-            result_columns.reserve(columns.size());
-            offset += max_curr_len;
-            for (size_t i = 0; i < columns.size(); ++i) {
-                auto& e = columns[i];
-                if (arrow::Datum::Kind::CHUNKED_ARRAY == e.kind()) {
-                    result_columns.emplace_back(e.chunked_array()->chunk(currentChunk[i])->Slice(inChunkOffset[i], max_curr_len));
-                    if (max_curr_len + inChunkOffset[i] == e.chunked_array()->chunk(currentChunk[i])->length()) {
-                        ++currentChunk[i];
-                        inChunkOffset[i] = 0;
-                    } else {
-                        inChunkOffset[i] += max_curr_len;
-                    }
-                } else {
-                    result_columns.emplace_back(e.array()->Slice(offset - max_curr_len, max_curr_len));
-                }
-            }
-            blocks.emplace_back(std::make_shared<TResultBatch>(max_curr_len, std::move(result_columns)));
-        }
-        return blocks;
+        auto res = std::make_shared<TResultBatch>(RowsCnt_, std::move(columns));
+        RowsCnt_ = 0;
+        return res;
     }
 
 private:
@@ -480,9 +447,7 @@ class TSource : public TNonCopyable {
                 }
             }
             if (payload) {
-                for (auto &e: FallbackHandler(inputIdx, payload)) {
-                    Listener_->HandleFallback(std::move(e));
-                }
+                Listener_->HandleFallback(FallbackHandler(inputIdx, payload));
                 InputDone(inputIdx);
                 RunRead();
             }
@@ -494,7 +459,7 @@ class TSource : public TNonCopyable {
         }
     }
 
-    std::vector<TResultBatch::TPtr> FallbackHandler(size_t idx, NYT::TSharedRef payload) {
+    TResultBatch::TPtr FallbackHandler(size_t idx, NYT::TSharedRef payload) {
         if (!payload.Size()) {
             return {};
         }