fix some comments

Author: gty404

src/iceberg/table_scan.cc

@@ -50,23 +50,25 @@ TableScanBuilder& TableScanBuilder::WithFilter(
 }
 
 Result<std::unique_ptr<TableScan>> TableScanBuilder::Build() {
-  ICEBERG_ASSIGN_OR_RAISE(auto snapshot, snapshot_id_ ? table_.snapshot(*snapshot_id_)
-                                                      : Result<std::shared_ptr<Snapshot>>(
-                                                            table_.current_snapshot()));
-
-  auto ResolveSchema = [&]() -> Result<std::shared_ptr<Schema>> {
-    if (snapshot->schema_id) {
-      const auto& schemas = table_.schemas();
-      if (auto it = schemas.find(*snapshot->schema_id); it != schemas.end()) {
-        return it->second;
-      }
+  std::shared_ptr<Snapshot> snapshot;
+  if (snapshot_id_) {
+    ICEBERG_ASSIGN_OR_RAISE(snapshot, table_.snapshot(*snapshot_id_));
+  } else {
+    snapshot = table_.current_snapshot();
+  }
+
+  std::shared_ptr<Schema> schema;
+  if (snapshot->schema_id) {
+    const auto& schemas = table_.schemas();
+    if (auto it = schemas.find(*snapshot->schema_id); it != schemas.end()) {
+      schema = it->second;
+    } else {
       return InvalidData("Schema {} in snapshot {} is not found", *snapshot->schema_id,
                          snapshot->snapshot_id);
     }
-    return table_.schema();
-  };
-
-  ICEBERG_ASSIGN_OR_RAISE(auto schema, ResolveSchema());
+  } else {
+    schema = table_.schema();
+  }
 
   std::vector<int32_t> field_ids;
   field_ids.reserve(column_names_.size());
@@ -78,18 +80,19 @@ Result<std::unique_ptr<TableScan>> TableScanBuilder::Build() {
     field_ids.emplace_back(field_opt.value().get().field_id());
   }
 
-  auto context = std::make_unique<TableScan::ScanContext>(
-      std::move(snapshot), std::move(schema), std::move(field_ids), std::move(filter_));
+  TableScan::ScanContext context{.snapshot = std::move(snapshot),
+                                 .schema = std::move(schema),
+                                 .field_ids = std::move(field_ids),
+                                 .filter = std::move(filter_)};
   return std::make_unique<TableScan>(std::move(context), table_.io());
 }
 
-TableScan::TableScan(std::unique_ptr<ScanContext> context,
-                     std::shared_ptr<FileIO> file_io)
+TableScan::TableScan(ScanContext context, std::shared_ptr<FileIO> file_io)
     : context_(std::move(context)), file_io_(std::move(file_io)) {}
 
 Result<std::vector<std::shared_ptr<FileScanTask>>> TableScan::PlanFiles() const {
   ICEBERG_ASSIGN_OR_RAISE(auto manifest_list_reader,
-                          CreateManifestListReader(context_->snapshot_->manifest_list));
+                          CreateManifestListReader(context_.snapshot->manifest_list));
   ICEBERG_ASSIGN_OR_RAISE(auto manifest_files, manifest_list_reader->Files());
 
   std::vector<std::shared_ptr<FileScanTask>> tasks;
@@ -102,8 +105,8 @@ Result<std::vector<std::shared_ptr<FileScanTask>>> TableScan::PlanFiles() const
       const auto& data_file = manifest->data_file;
       tasks.emplace_back(std::make_shared<FileScanTask>(
           data_file.file_path, 0, data_file.file_size_in_bytes, data_file.record_count,
-          data_file.content, data_file.file_format, context_->schema_,
-          context_->field_ids_, context_->filter_));
+          data_file.content, data_file.file_format, context_.schema, context_.field_ids,
+          context_.filter));
     }
   }
   return tasks;

src/iceberg/table_scan.h

@@ -22,8 +22,6 @@
 #include <string>
 #include <vector>
 
-#include "iceberg/expression/expression.h"
-#include "iceberg/file_io.h"
 #include "iceberg/manifest_entry.h"
 #include "iceberg/type_fwd.h"
 
@@ -42,6 +40,7 @@ class ICEBERG_EXPORT TableScanBuilder {
   TableScanBuilder& WithSnapshotId(int64_t snapshot_id);
 
   /// \brief Selects columns to include in the scan.
+  /// Defaults to none which means select all columns
   /// \param column_names A list of column names.
   /// \return Reference to the builder.
   TableScanBuilder& WithColumnNames(const std::vector<std::string>& column_names);
@@ -67,16 +66,16 @@ class ICEBERG_EXPORT TableScan {
  public:
   /// \brief Scan context holding snapshot and scan-specific metadata.
   struct ScanContext {
-    std::shared_ptr<Snapshot> snapshot_;  ///< Snapshot to scan.
-    std::shared_ptr<Schema> schema_;      ///< Projected schema.
-    std::vector<int32_t> field_ids_;      ///< Field IDs of selected columns.
-    std::shared_ptr<Expression> filter_;  ///< Filter expression to apply.
+    std::shared_ptr<Snapshot> snapshot;  ///< Snapshot to scan.
+    std::shared_ptr<Schema> schema;      ///< Table schema.
+    std::vector<int32_t> field_ids;      ///< Field IDs of selected columns.
+    std::shared_ptr<Expression> filter;  ///< Filter expression to apply.
   };
 
   /// \brief Constructs a TableScan with the given context and file I/O.
   /// \param context Scan context including snapshot, schema, and filter.
   /// \param file_io File I/O instance for reading manifests and data files.
-  TableScan(std::unique_ptr<ScanContext> context, std::shared_ptr<FileIO> file_io);
+  TableScan(ScanContext context, std::shared_ptr<FileIO> file_io);
 
   /// \brief Plans the scan tasks by resolving manifests and data files.
   ///
@@ -97,7 +96,7 @@ class ICEBERG_EXPORT TableScan {
   Result<std::unique_ptr<ManifestReader>> CreateManifestReader(
       const std::string& file_path) const;
 
-  std::unique_ptr<ScanContext> context_;
+  ScanContext context_;
   std::shared_ptr<FileIO> file_io_;
 };
 
@@ -109,7 +108,7 @@ struct ICEBERG_EXPORT FileScanTask {
   std::optional<uint64_t> record_count;  ///< Optional number of records.
   DataFile::Content file_content;        ///< Type of file content.
   FileFormatType file_format;            ///< Format of the data file.
-  std::shared_ptr<Schema> schema;        ///< Projected schema.
+  std::shared_ptr<Schema> schema;        ///< Table schema.
   std::vector<int32_t> field_ids;        ///< Field IDs to project.
   std::shared_ptr<Expression> filter;    ///< Filter expression to apply.
 };

src/iceberg/type_fwd.h

@@ -91,10 +91,7 @@ class LocationProvider;
 class SortField;
 class SortOrder;
 class Table;
-class TableScan;
-struct FileScanTask;
 class FileIO;
-class TableScanBuilder;
 class Transaction;
 class Transform;
 class TransformFunction;
@@ -112,6 +109,12 @@ class NameMapping;
 enum class SnapshotRefType;
 enum class TransformType;
 
+class Expression;
+
+struct FileScanTask;
+class TableScan;
+class TableScanBuilder;
+
 /// ----------------------------------------------------------------------------
 /// TODO: Forward declarations below are not added yet.
 /// ----------------------------------------------------------------------------