fix: storage v2 write mmap file per field per cell (#42180)

Each cell of a field should be written to its own mmap file, rather than
writing all cells of the field into a single mmap file.
related: #39173

---------

Signed-off-by: shaoting-huang <shaoting.huang@zilliz.com>

internal/core/src/segcore/storagev2translator/GroupChunkTranslator.cpp

@@ -82,12 +82,6 @@ GroupChunkTranslator::GroupChunkTranslator(
 }
 
 GroupChunkTranslator::~GroupChunkTranslator() {
-    for (auto chunk : group_chunks_) {
-        if (chunk != nullptr) {
-            // let the GroupChunk to be deleted by the unique_ptr
-            auto chunk_ptr = std::unique_ptr<GroupChunk>(chunk);
-        }
-    }
 }
 
 size_t
@@ -166,77 +160,31 @@ GroupChunkTranslator::get_cells(const std::vector<cachinglayer::cid_t>& cids) {
     LOG_INFO("segment {} submits load fields {} task to thread pool",
              segment_id_,
              field_id_list_.ToString());
-    if (!use_mmap_) {
-        load_column_group_in_memory();
-    } else {
-        load_column_group_in_mmap();
-    }
 
-    for (auto cid : cids) {
+    std::shared_ptr<milvus::ArrowDataWrapper> r;
-        AssertInfo(group_chunks_[cid] != nullptr,
+    int64_t cid_idx = 0;
-                   "GroupChunkTranslator::get_cells failed to load cell {} of "
+    int64_t total_tables = 0;
-                   "CacheSlot {}.",
+    while (column_group_info_.arrow_reader_channel->pop(r)) {
-                   cid,
+        for (const auto& table : r->arrow_tables) {
-                   key_);
+            AssertInfo(cid_idx < cids.size(),
-        cells.emplace_back(
+                       "Number of tables exceed number of cids ({})",
-            cid, std::unique_ptr<milvus::GroupChunk>(group_chunks_[cid]));
+                       cids.size());
-        group_chunks_[cid] = nullptr;
+            auto cid = cids[cid_idx++];
+            cells.emplace_back(cid, load_group_chunk(table, cid));
+            total_tables++;
         }
+    }
+    AssertInfo(total_tables == cids.size(),
+               "Number of tables ({}) does not match number of cids ({})",
+               total_tables,
+               cids.size());
     return cells;
 }
 
-void
+std::unique_ptr<milvus::GroupChunk>
-GroupChunkTranslator::load_column_group_in_memory() {
+GroupChunkTranslator::load_group_chunk(
-    std::vector<size_t> row_counts(field_id_list_.size(), 0);
+    const std::shared_ptr<arrow::Table>& table,
-    std::shared_ptr<milvus::ArrowDataWrapper> r;
+    const milvus::cachinglayer::cid_t cid) {
-    std::vector<std::string> files;
-    std::vector<size_t> file_offsets;
-    while (column_group_info_.arrow_reader_channel->pop(r)) {
-        for (const auto& table : r->arrow_tables) {
-            process_batch(table, files, file_offsets, row_counts);
-        }
-    }
-}
-
-void
-GroupChunkTranslator::load_column_group_in_mmap() {
-    std::vector<std::string> files;
-    std::vector<size_t> file_offsets;
-    std::vector<size_t> row_counts;
-
-    // Initialize files and offsets
-    for (size_t i = 0; i < field_id_list_.size(); ++i) {
-        auto field_id = field_id_list_.Get(i);
-        auto filepath =
-            std::filesystem::path(column_group_info_.mmap_dir_path) /
-            std::to_string(segment_id_) / std::to_string(field_id);
-        auto dir = filepath.parent_path();
-        std::filesystem::create_directories(dir);
-        files.push_back(filepath.string());
-        file_offsets.push_back(0);
-        row_counts.push_back(0);
-    }
-
-    std::shared_ptr<milvus::ArrowDataWrapper> r;
-    while (column_group_info_.arrow_reader_channel->pop(r)) {
-        for (const auto& table : r->arrow_tables) {
-            process_batch(table, files, file_offsets, row_counts);
-        }
-    }
-    for (size_t i = 0; i < files.size(); ++i) {
-        auto ok = unlink(files[i].c_str());
-        AssertInfo(ok == 0,
-                   fmt::format("failed to unlink mmap data file {}, err: {}",
-                               files[i].c_str(),
-                               strerror(errno)));
-    }
-}
-
-void
-GroupChunkTranslator::process_batch(const std::shared_ptr<arrow::Table>& table,
-                                    const std::vector<std::string>& files,
-                                    std::vector<size_t>& file_offsets,
-                                    std::vector<size_t>& row_counts) {
     // Create chunks for each field in this batch
     std::unordered_map<FieldId, std::shared_ptr<Chunk>> chunks;
     // Iterate through field_id_list to get field_id and create chunk
@@ -263,25 +211,35 @@ GroupChunkTranslator::process_batch(const std::shared_ptr<arrow::Table>& table,
             chunk = create_chunk(field_meta, dim, array_vec);
         } else {
             // Mmap mode
-            int flags = O_RDWR;
+            auto filepath =
-            if (file_offsets[i] == 0) {
+                std::filesystem::path(column_group_info_.mmap_dir_path) /
-                // First write to this file, create and truncate
+                std::to_string(segment_id_) / std::to_string(field_id) /
-                flags |= O_CREAT | O_TRUNC;
+                std::to_string(cid);
-            }
+
-            auto file = File::Open(files[i], flags);
+            LOG_INFO(
-            // should seek to the file offset before writing
+                "storage v2 segment {} mmaping field {} chunk {} to path {}",
-            file.Seek(file_offsets[i], SEEK_SET);
+                segment_id_,
-            chunk =
+                field_id,
-                create_chunk(field_meta, dim, file, file_offsets[i], array_vec);
+                cid,
-            file_offsets[i] += chunk->Size();
+                filepath.string());
+
+            std::filesystem::create_directories(filepath.parent_path());
+
+            auto file =
+                File::Open(filepath.string(), O_CREAT | O_TRUNC | O_RDWR);
+            auto chunk = create_chunk(field_meta, dim, file, 0, array_vec);
+            auto ok = unlink(filepath.c_str());
+            AssertInfo(
+                ok == 0,
+                fmt::format(
+                    "storage v2 failed to unlink mmap data file {}, err: {}",
+                    filepath.c_str(),
+                    strerror(errno)));
         }
 
-        row_counts[i] += chunk->RowNums();
         chunks[fid] = std::move(chunk);
     }
-    // Create GroupChunk from chunks and store in results
+    return std::make_unique<milvus::GroupChunk>(chunks);
-    auto group_chunk = std::make_unique<milvus::GroupChunk>(chunks);
-    group_chunks_.emplace_back(group_chunk.release());
 }
 
 }  // namespace milvus::segcore::storagev2translator

internal/core/src/segcore/storagev2translator/GroupChunkTranslator.h

@@ -72,17 +72,9 @@ class GroupChunkTranslator
     }
 
  private:
-    void
+    std::unique_ptr<milvus::GroupChunk>
-    load_column_group_in_memory();
+    load_group_chunk(const std::shared_ptr<arrow::Table>& table,
-
+                     const milvus::cachinglayer::cid_t cid);
-    void
-    load_column_group_in_mmap();
-
-    void
-    process_batch(const std::shared_ptr<arrow::Table>& table,
-                  const std::vector<std::string>& files,
-                  std::vector<size_t>& file_offsets,
-                  std::vector<size_t>& row_counts);
 
     int64_t segment_id_;
     std::string key_;
@@ -96,7 +88,6 @@ class GroupChunkTranslator
     ChunkedSegmentSealedImpl* chunked_segment_;
     std::unique_ptr<milvus::segcore::InsertRecord<true>> ir_;
     GroupCTMeta meta_;
-    std::vector<milvus::GroupChunk*> group_chunks_;
     int64_t timestamp_offet_;
     bool use_mmap_;
 };