refactoring of reading from compact parts

CurtizJ · CurtizJ · commit 13b27a8d3663 · 2024-03-18T16:13:02.000Z
diff --git a/src/Storages/MergeTree/MergeTreeReaderCompact.cpp b/src/Storages/MergeTree/MergeTreeReaderCompact.cpp
@@ -78,31 +78,7 @@ void MergeTreeReaderCompact::fillColumnPositions()
         /// we have to read its offsets if they exist.
         if (!position && is_array)
         {
-            NameAndTypePair column_to_read_with_subcolumns = column_to_read;
-            auto [name_in_storage, subcolumn_name] = Nested::splitName(column_to_read.name);
-
-            /// If it is a part of Nested, we need to get the column from
-            /// storage metadata which is converted to Nested type with subcolumns.
-            /// It is required for proper counting of shared streams.
-            if (!subcolumn_name.empty())
-            {
-                /// If column is renamed get the new name from storage metadata.
-                if (alter_conversions->columnHasNewName(name_in_storage))
-                    name_in_storage = alter_conversions->getColumnNewName(name_in_storage);
-
-                if (!storage_columns_with_collected_nested)
-                {
-                    auto options = GetColumnsOptions(GetColumnsOptions::AllPhysical).withExtendedObjects();
-                    auto storage_columns_list = Nested::collect(storage_snapshot->getColumns(options));
-                    storage_columns_with_collected_nested = ColumnsDescription(std::move(storage_columns_list));
-                }
-
-                column_to_read_with_subcolumns = storage_columns_with_collected_nested
-                    ->getColumnOrSubcolumn(
-                        GetColumnsOptions::All,
-                        Nested::concatenateName(name_in_storage, subcolumn_name));
-            }
-
+            auto column_to_read_with_subcolumns = getColumnConvertedToSubcolumnOfNested(column_to_read);
             auto name_level_for_offsets = findColumnForOffsets(column_to_read_with_subcolumns);
 
             if (name_level_for_offsets.has_value())
@@ -119,6 +95,35 @@ void MergeTreeReaderCompact::fillColumnPositions()
     }
 }
 
+NameAndTypePair MergeTreeReaderCompact::getColumnConvertedToSubcolumnOfNested(const NameAndTypePair & column)
+{
+    if (!isArray(column.type))
+        return column;
+
+    /// If it is a part of Nested, we need to get the column from
+    /// storage metadata which is converted to Nested type with subcolumns.
+    /// It is required for proper counting of shared streams.
+    auto [name_in_storage, subcolumn_name] = Nested::splitName(column.name);
+
+    if (subcolumn_name.empty())
+        return column;
+
+    /// If column is renamed get the new name from storage metadata.
+    if (alter_conversions->columnHasNewName(name_in_storage))
+        name_in_storage = alter_conversions->getColumnNewName(name_in_storage);
+
+    if (!storage_columns_with_collected_nested)
+    {
+        auto options = GetColumnsOptions(GetColumnsOptions::AllPhysical).withExtendedObjects();
+        auto storage_columns_list = Nested::collect(storage_snapshot->getColumns(options));
+        storage_columns_with_collected_nested = ColumnsDescription(std::move(storage_columns_list));
+    }
+
+    return storage_columns_with_collected_nested->getColumnOrSubcolumn(
+        GetColumnsOptions::All,
+        Nested::concatenateName(name_in_storage, subcolumn_name));
+}
+
 void MergeTreeReaderCompact::readData(
     const NameAndTypePair & name_and_type,
     ColumnPtr & column,
diff --git a/src/Storages/MergeTree/MergeTreeReaderCompact.h b/src/Storages/MergeTree/MergeTreeReaderCompact.h
@@ -31,10 +31,11 @@ class MergeTreeReaderCompact : public IMergeTreeReader
         const ReadBufferFromFileBase::ProfileCallback & profile_callback_,
         clockid_t clock_type_);
 
-    bool canReadIncompleteGranules() const override final { return false; }
+    bool canReadIncompleteGranules() const final { return false; }
 
 protected:
     void fillColumnPositions();
+    NameAndTypePair getColumnConvertedToSubcolumnOfNested(const NameAndTypePair & column);
 
     using InputStreamGetter = ISerialization::InputStreamGetter;
 
