try to fix Nested

src/DataTypes/Serializations/ISerialization.cpp

@@ -224,7 +224,11 @@ String ISerialization::getSubcolumnNameForStream(const SubstreamPath & path, siz
 
 void ISerialization::addToSubstreamsCache(SubstreamsCache * cache, const SubstreamPath & path, ColumnPtr column)
 {
-    if (cache && !path.empty())
+    if (!cache || path.empty())
+        return;
+
+    auto subcolumn_name = getSubcolumnNameForStream(path);
+    if (!subcolumn_name.empty())
         cache->emplace(getSubcolumnNameForStream(path), column);
 }
 

src/Storages/MergeTree/IMergeTreeDataPart.cpp

@@ -448,12 +448,7 @@ void IMergeTreeDataPart::setColumns(const NamesAndTypesList & new_columns)
     for (const auto & column : columns)
         column_name_to_position.emplace(column.name, pos++);
 
-    /// For wide parts convert plain arrays to Nested for
-    /// more convinient managing of shared offsets column.
-    if (part_type == Type::Wide)
-        columns_description = ColumnsDescription(Nested::collect(columns));
-    else
-        columns_description = ColumnsDescription(columns);
+    columns_description = ColumnsDescription(columns);
 }
 
 NameAndTypePair IMergeTreeDataPart::getColumn(const String & column_name) const

src/Storages/MergeTree/IMergeTreeDataPart.h

@@ -136,6 +136,7 @@ public:
     void setColumns(const NamesAndTypesList & new_columns);
 
     const NamesAndTypesList & getColumns() const { return columns; }
+    const ColumnsDescription & getColumnsDescription() const { return columns_description; }
 
     NameAndTypePair getColumn(const String & name) const;
     std::optional<NameAndTypePair> tryGetColumn(const String & column_name) const;

src/Storages/MergeTree/IMergeTreeReader.h

@@ -55,16 +55,14 @@ public:
     const NamesAndTypesList & getColumns() const { return columns; }
     size_t numColumnsInResult() const { return columns.size(); }
 
-    size_t getFirstMarkToRead() const
-    {
-        return all_mark_ranges.front().begin;
-    }
+    size_t getFirstMarkToRead() const { return all_mark_ranges.front().begin; }
 
     MergeTreeData::DataPartPtr data_part;
 
 protected:
     /// Returns actual column name in part, which can differ from table metadata.
     String getColumnNameInPart(const NameAndTypePair & required_column) const;
+
     /// Returns actual column name and type in part, which can differ from table metadata.
     NameAndTypePair getColumnInPart(const NameAndTypePair & required_column) const;
 

src/Storages/MergeTree/MergeTreeDataPartWide.cpp

@@ -49,7 +49,7 @@ IMergeTreeDataPart::MergeTreeReaderPtr MergeTreeDataPartWide::getReader(
 {
     auto ptr = std::static_pointer_cast<const MergeTreeDataPartWide>(shared_from_this());
     return std::make_unique<MergeTreeReaderWide>(
-        ptr, Nested::convertToSubcolumns(columns_to_read),
+        ptr, columns_to_read,
         metadata_snapshot, uncompressed_cache,
         mark_cache, mark_ranges, reader_settings,
         avg_value_size_hints, profile_callback);
@@ -66,7 +66,7 @@ IMergeTreeDataPart::MergeTreeWriterPtr MergeTreeDataPartWide::getWriter(
 {
     return std::make_unique<MergeTreeDataPartWriterWide>(
         shared_from_this(), data_part_storage_builder,
-        Nested::convertToSubcolumns(columns_list), metadata_snapshot, indices_to_recalc,
+        columns_list, metadata_snapshot, indices_to_recalc,
         index_granularity_info.marks_file_extension,
         default_codec_, writer_settings, computed_index_granularity);
 }

src/Storages/MergeTree/MergeTreeReaderWide.cpp

@@ -4,6 +4,7 @@
 #include <Columns/ColumnSparse.h>
 #include <DataTypes/DataTypeArray.h>
 #include <DataTypes/NestedUtils.h>
+#include <DataTypes/DataTypeNested.h>
 #include <Interpreters/inplaceBlockConversions.h>
 #include <Storages/MergeTree/IMergeTreeReader.h>
 #include <Storages/MergeTree/MergeTreeDataPartWide.h>
@@ -60,6 +61,19 @@ MergeTreeReaderWide::MergeTreeReaderWide(
     }
 }
 
+String MergeTreeReaderWide::getNameForSubstreamCache(const NameAndTypePair & column) const
+{
+    if (!column.isSubcolumn() && isArray(column.type))
+    {
+        auto split = Nested::splitName(column.name);
+        const auto & part_columns = data_part->getColumnsDescription();
+
+        if (!split.second.empty() && part_columns.hasNested(split.first))
+            return split.first;
+    }
+
+    return column.getNameInStorage();
+}
 
 size_t MergeTreeReaderWide::readRows(
     size_t from_mark, size_t current_task_last_mark, bool continue_reading, size_t max_rows_to_read, Columns & res_columns)
@@ -86,7 +100,7 @@ size_t MergeTreeReaderWide::readRows(
                 auto column_from_part = getColumnInPart(*name_and_type);
                 try
                 {
-                    auto & cache = caches[column_from_part.getNameInStorage()];
+                    auto & cache = caches[getNameForSubstreamCache(column_from_part)];
                     prefetch(column_from_part, from_mark, continue_reading, current_task_last_mark, cache, prefetched_streams);
                 }
                 catch (Exception & e)
@@ -117,7 +131,7 @@ size_t MergeTreeReaderWide::readRows(
             try
             {
                 size_t column_size_before_reading = column->size();
-                auto & cache = caches[column_from_part.getNameInStorage()];
+                auto & cache = caches[getNameForSubstreamCache(column_from_part)];
 
                 readData(
                     column_from_part, column, from_mark, continue_reading, current_task_last_mark,

src/Storages/MergeTree/MergeTreeReaderWide.h

@@ -38,6 +38,8 @@ public:
 private:
     FileStreams streams;
 
+    String getNameForSubstreamCache(const NameAndTypePair & column) const;
+
     void addStreams(const NameAndTypePair & name_and_type,
         const ReadBufferFromFileBase::ProfileCallback & profile_callback, clockid_t clock_type);