allow to extract subcolumns from column

src/DataTypes/DataTypeArray.cpp

@@ -509,17 +509,25 @@ DataTypePtr DataTypeArray::getSubcolumnType(const String & subcolumn_name) const
     if (checkString("size", buf) && tryReadIntText(dim, buf) && dim < getNumberOfDimensions())
         return std::make_shared<DataTypeUInt64>();
 
-    return nullptr;
+    return std::make_shared<DataTypeArray>(nested->getSubcolumnType(subcolumn_name));
 }
 
-std::vector<String> DataTypeArray::getSubcolumnNames() const
+MutableColumnPtr DataTypeArray::getSubcolumn(const String & subcolumn_name, IColumn & column) const
 {
-    size_t num_of_dimentions = getNumberOfDimensions();
-    std::vector<String> res(num_of_dimentions);
-    for (size_t i = 0; i < num_of_dimentions; ++i)
-        res[i] = "size" + std::to_string(i);
+    return getSubcolumnImpl(subcolumn_name, column, 0);
+}
 
-    return res;
+MutableColumnPtr DataTypeArray::getSubcolumnImpl(const String & subcolumn_name, IColumn & column, size_t level) const
+{
+    auto & column_array = assert_cast<ColumnArray &>(column);
+    if (subcolumn_name == "size" + std::to_string(level))
+        return column_array.getOffsetsPtr()->assumeMutable();
+
+    if (const auto * nested_array = typeid_cast<const DataTypeArray *>(nested.get()))
+        return nested_array->getSubcolumnImpl(subcolumn_name, column, level + 1);
+
+    auto subcolumn = nested->getSubcolumn(subcolumn_name, column_array.getData());
+    return ColumnArray::create(std::move(subcolumn), column_array.getOffsetsPtr()->assumeMutable());
 }
 
 String DataTypeArray::getEscapedFileName(const NameAndTypePair & column) const

src/DataTypes/DataTypeArray.h

@@ -112,13 +112,17 @@ public:
     }
 
     DataTypePtr getSubcolumnType(const String & subcolumn_name) const override;
-    std::vector<String> getSubcolumnNames() const override;
+    MutableColumnPtr getSubcolumn(const String & subcolumn_name, IColumn & column) const override;
+
     String getEscapedFileName(const NameAndTypePair & column) const override;
 
     const DataTypePtr & getNestedType() const { return nested; }
 
     /// 1 for plain array, 2 for array of arrays and so on.
     size_t getNumberOfDimensions() const;
+
+private:
+    MutableColumnPtr getSubcolumnImpl(const String & subcolumn_name, IColumn & column, size_t level) const;
 };
 
 }

src/DataTypes/DataTypeLowCardinality.h

@@ -23,6 +23,7 @@ public:
     TypeIndex getTypeId() const override { return TypeIndex::LowCardinality; }
 
     void enumerateStreams(const StreamCallback & callback, SubstreamPath & path) const override;
+    DataTypePtr getSubcolumnType(const String & /* subcolumn_name */) const override { return shared_from_this(); }
 
     void serializeBinaryBulkStatePrefix(
             SerializeBinaryBulkSettings & settings,

src/DataTypes/DataTypeNullable.cpp

@@ -529,15 +529,20 @@ bool DataTypeNullable::equals(const IDataType & rhs) const
 
 DataTypePtr DataTypeNullable::getSubcolumnType(const String & subcolumn_name) const
 {
+    std::cerr << "(DataTypeNullable::getSubcolumnType) subcolumn_name: " << subcolumn_name << "\n";
     if (subcolumn_name == "null")
         return std::make_shared<DataTypeUInt8>();
 
-    return nullptr;
+    return nested_data_type->getSubcolumnType(subcolumn_name);
 }
 
-std::vector<String> DataTypeNullable::getSubcolumnNames() const
+MutableColumnPtr DataTypeNullable::getSubcolumn(const String & subcolumn_name, IColumn & column) const
 {
-    return {"null"};
+    auto & column_nullable = assert_cast<ColumnNullable &>(column);
+    if (subcolumn_name == "null")
+        return column_nullable.getNullMapColumnPtr()->assumeMutable();
+
+    return nested_data_type->getSubcolumn(subcolumn_name, column_nullable.getNestedColumn());
 }
 
 String DataTypeNullable::getEscapedFileName(const NameAndTypePair & column) const

src/DataTypes/DataTypeNullable.h

@@ -98,7 +98,7 @@ public:
     bool onlyNull() const override;
     bool canBeInsideLowCardinality() const override { return nested_data_type->canBeInsideLowCardinality(); }
     DataTypePtr getSubcolumnType(const String & subcolumn_name) const override;
-    std::vector<String> getSubcolumnNames() const override;
+    MutableColumnPtr getSubcolumn(const String & subcolumn_name, IColumn & column) const override;
     String getEscapedFileName(const NameAndTypePair & column) const override;
 
     const DataTypePtr & getNestedType() const { return nested_data_type; }

src/DataTypes/DataTypeTuple.cpp

@@ -10,6 +10,7 @@
 #include <Common/typeid_cast.h>
 #include <Common/assert_cast.h>
 #include <Common/quoteString.h>
+#include <Common/escapeForFileName.h>
 #include <IO/WriteHelpers.h>
 #include <IO/ReadHelpers.h>
 #include <IO/WriteBufferFromString.h>
@@ -31,6 +32,7 @@ namespace ErrorCodes
     extern const int DUPLICATE_COLUMN;
     extern const int BAD_ARGUMENTS;
     extern const int NOT_FOUND_COLUMN_IN_BLOCK;
+    extern const int ILLEGAL_COLUMN;
 }
 
 
@@ -419,6 +421,14 @@ void DataTypeTuple::deserializeBinaryBulkWithMultipleStreams(
     settings.path.pop_back();
 }
 
+String DataTypeTuple::getEscapedFileName(const NameAndTypePair & column) const
+{
+    if (column.isSubcolumn())
+        return escapeForFileName(column.getStorageName()) + "%2E" + column.getSubcolumnName();
+
+    return escapeForFileName(column.name);
+}
+
 void DataTypeTuple::serializeProtobuf(const IColumn & column, size_t row_num, ProtobufWriter & protobuf, size_t & value_index) const
 {
     for (; value_index < elems.size(); ++value_index)
@@ -531,12 +541,40 @@ size_t DataTypeTuple::getSizeOfValueInMemory() const
 
 DataTypePtr DataTypeTuple::getSubcolumnType(const String & subcolumn_name) const
 {
-    return elems[getPositionByName(subcolumn_name)];
+    for (size_t i = 0; i < names.size(); ++i)
+    {
+        if (startsWith(subcolumn_name, names[i]))
+        {
+            size_t name_length = names[i].size();
+            if (subcolumn_name.size() == name_length)
+                return elems[i];
+
+            if (subcolumn_name[name_length] == '.')
+                return elems[i]->getSubcolumnType(subcolumn_name.substr(name_length + 1));
+        }
     }
 
-std::vector<String> DataTypeTuple::getSubcolumnNames() const
+    throw Exception(ErrorCodes::ILLEGAL_COLUMN, "There is no subcolumn {} in type {}", subcolumn_name, getName());
+}
+
+MutableColumnPtr DataTypeTuple::getSubcolumn(const String & subcolumn_name, IColumn & column) const
 {
-    return names;
+    for (size_t i = 0; i < names.size(); ++i)
+    {
+        if (startsWith(subcolumn_name, names[i]))
+        {
+            size_t name_length = names[i].size();
+            auto & subcolumn = extractElementColumn(column, i);
+
+            if (subcolumn_name.size() == name_length)
+                return subcolumn.assumeMutable();
+
+            if (subcolumn_name[name_length] == '.')
+                return elems[i]->getSubcolumn(subcolumn_name.substr(name_length + 1), subcolumn);
+        }
+    }
+
+    throw Exception(ErrorCodes::ILLEGAL_COLUMN, "There is no subcolumn {} in type {}", subcolumn_name, getName());
 }
 
 

src/DataTypes/DataTypeTuple.h

@@ -94,8 +94,10 @@ public:
     bool haveMaximumSizeOfValue() const override;
     size_t getMaximumSizeOfValueInMemory() const override;
     size_t getSizeOfValueInMemory() const override;
+
     DataTypePtr getSubcolumnType(const String & subcolumn_name) const override;
-    std::vector<String> getSubcolumnNames() const override;
+    MutableColumnPtr getSubcolumn(const String & subcolumn_name, IColumn & column) const override;
+    String getEscapedFileName(const NameAndTypePair & column) const override;
 
     const DataTypes & getElements() const { return elems; }
     const Strings & getElementNames() const { return names; }

src/DataTypes/IDataType.cpp

@@ -18,6 +18,7 @@ namespace ErrorCodes
     extern const int MULTIPLE_STREAMS_REQUIRED;
     extern const int LOGICAL_ERROR;
     extern const int DATA_TYPE_CANNOT_BE_PROMOTED;
+    extern const int ILLEGAL_COLUMN;
 }
 
 IDataType::IDataType() : custom_name(nullptr), custom_text_serialization(nullptr)
@@ -92,19 +93,83 @@ size_t IDataType::getSizeOfValueInMemory() const
     throw Exception("Value of type " + getName() + " in memory is not of fixed size.", ErrorCodes::LOGICAL_ERROR);
 }
 
+DataTypePtr IDataType::getSubcolumnType(const String & subcolumn_name) const
+{
+    throw Exception(ErrorCodes::ILLEGAL_COLUMN, "There is no subcolumn {} in type {}", subcolumn_name, getName());
+}
+
+MutableColumnPtr IDataType::getSubcolumn(const String & subcolumn_name, IColumn &) const
+{
+    throw Exception(ErrorCodes::ILLEGAL_COLUMN, "There is no subcolumn {} in type {}", subcolumn_name, getName());
+}
+
+std::vector<String> IDataType::getSubcolumnNames() const
+{
+    std::vector<String> res;
+    enumerateStreams([&res](const IDataType::SubstreamPath & substream_path, const IDataType & /* substream_type */)
+    {
+        auto subcolumn_name = IDataType::getSubcolumnNameForStream("", substream_path);
+        if (!subcolumn_name.empty())
+            res.push_back(subcolumn_name.substr(1)); // It starts with a dot.
+    });
+
+    return res;
+}
+
 String IDataType::getEscapedFileName(const NameAndTypePair & column) const
 {
     return escapeForFileName(column.name);
 }
 
+static String getNameForSubstreamPath(
+    String stream_name,
+    const IDataType::SubstreamPath & path,
+    const String & tuple_element_delimeter = ".")
+{
+    size_t array_level = 0;
+    for (const auto & elem : path)
+    {
+        if (elem.type == IDataType::Substream::NullMap)
+            stream_name += ".null";
+        else if (elem.type == IDataType::Substream::ArraySizes)
+            stream_name += ".size" + toString(array_level);
+        else if (elem.type == IDataType::Substream::ArrayElements)
+            ++array_level;
+        else if (elem.type == IDataType::Substream::TupleElement)
+            stream_name += tuple_element_delimeter + escapeForFileName(elem.tuple_element_name);
+        else if (elem.type == IDataType::Substream::DictionaryKeys)
+            stream_name += ".dict";
+    }
+
+    return stream_name;
+}
+
+
+/// FIXME: rewrite it.
 String IDataType::getFileNameForStream(const NameAndTypePair & column, const IDataType::SubstreamPath & path)
 {
-
     if (!column.isSubcolumn())
         return getFileNameForStream(column.name, path);
 
-    auto stream_name = column.getStorageType()->getEscapedFileName(column);
-    return getFileNameForStreamImpl(std::move(stream_name), path);
+    String storage_name = column.getStorageName();
+    String nested_table_name = Nested::extractTableName(storage_name);
+
+    bool is_sizes_of_nested_type =
+        (path.size() == 1 && path[0].type == IDataType::Substream::ArraySizes
+            && nested_table_name != storage_name) || column.getSubcolumnName() == "size0";
+
+    String stream_name;
+    if (is_sizes_of_nested_type)
+    {
+        if (column.getSubcolumnName() == "size0")
+            return escapeForFileName(nested_table_name) + ".size0";
+
+        stream_name = escapeForFileName(Nested::extractTableName(storage_name));
+    }
+    else
+        stream_name = column.getStorageType()->getEscapedFileName(column);
+
+    return getNameForSubstreamPath(std::move(stream_name), path, "%2E");
 }
 
 String IDataType::getFileNameForStream(const String & column_name, const IDataType::SubstreamPath & path)
@@ -119,36 +184,19 @@ String IDataType::getFileNameForStream(const String & column_name, const IDataTy
         && nested_table_name != column_name;
 
     auto stream_name = escapeForFileName(is_sizes_of_nested_type ? nested_table_name : column_name);
-    return getFileNameForStreamImpl(std::move(stream_name), path);
-}
 
-String IDataType::getFileNameForStreamImpl(String stream_name, const IDataType::SubstreamPath & path)
-{
-    size_t array_level = 0;
-    for (const Substream & elem : path)
-    {
-        if (elem.type == Substream::NullMap)
-            stream_name += ".null";
-        else if (elem.type == Substream::ArraySizes)
-            stream_name += ".size" + toString(array_level);
-        else if (elem.type == Substream::ArrayElements)
-            ++array_level;
-        else if (elem.type == Substream::TupleElement)
-        {
     /// For compatibility reasons, we use %2E instead of dot.
     /// Because nested data may be represented not by Array of Tuple,
     ///  but by separate Array columns with names in a form of a.b,
     ///  and name is encoded as a whole.
-            stream_name += "%2E" + escapeForFileName(elem.tuple_element_name);
-        }
-        else if (elem.type == Substream::DictionaryKeys)
-            stream_name += ".dict";
+    return getNameForSubstreamPath(std::move(stream_name), path, "%2E");
 }
 
-    return stream_name;
+String IDataType::getSubcolumnNameForStream(String stream_name, const SubstreamPath & path)
+{
+    return getNameForSubstreamPath(std::move(stream_name), path);
 }
 
-
 bool IDataType::isSpecialCompressionAllowed(const SubstreamPath & path)
 {
     for (const Substream & elem : path)

src/DataTypes/IDataType.h

@@ -37,7 +37,7 @@ struct NameAndTypePair;
   *
   * DataType is totally immutable object. You can always share them.
   */
-class IDataType : private boost::noncopyable
+class IDataType : private boost::noncopyable, public std::enable_shared_from_this<IDataType>
 {
 public:
     IDataType();
@@ -115,6 +115,10 @@ public:
     void enumerateStreams(const StreamCallback & callback, SubstreamPath && path) const { enumerateStreams(callback, path); }
     void enumerateStreams(const StreamCallback & callback) const { enumerateStreams(callback, {}); }
 
+    virtual DataTypePtr getSubcolumnType(const String & subcolumn_name) const;
+    virtual MutableColumnPtr getSubcolumn(const String & subcolumn_name, IColumn & column) const;
+    std::vector<String> getSubcolumnNames() const;
+
     using OutputStreamGetter = std::function<WriteBuffer*(const SubstreamPath &)>;
     using InputStreamGetter = std::function<ReadBuffer*(const SubstreamPath &)>;
 
@@ -152,6 +156,8 @@ public:
         bool position_independent_encoding = true;
         /// If not zero, may be used to avoid reallocations while reading column of String type.
         double avg_value_size_hint = 0;
+
+        std::vector<MutableColumnPtr> temporary_column_holders;
     };
 
     /// Call before serializeBinaryBulkWithMultipleStreams chain to write something before first mark.
@@ -230,9 +236,6 @@ public:
     virtual void serializeProtobuf(const IColumn & column, size_t row_num, ProtobufWriter & protobuf, size_t & value_index) const = 0;
     virtual void deserializeProtobuf(IColumn & column, ProtobufReader & protobuf, bool allow_add_row, bool & row_added) const = 0;
 
-    virtual DataTypePtr getSubcolumnType(const String & /* subcolumn_path */) const { return nullptr; }
-    virtual std::vector<String> getSubcolumnNames() const { return {}; }
-
     /** Text serialization with escaping but without quoting.
       */
     void serializeAsTextEscaped(const IColumn & column, size_t row_num, WriteBuffer & ostr, const FormatSettings &) const;
@@ -450,6 +453,7 @@ public:
 
     static String getFileNameForStream(const NameAndTypePair & column, const SubstreamPath & path);
     static String getFileNameForStream(const String & column_name, const SubstreamPath & path);
+    static String getSubcolumnNameForStream(String stream_name, const SubstreamPath & path);
 
     /// Substream path supports special compression methods like codec Delta.
     /// For all other substreams (like ArraySizes, NullMasks, etc.) we use only
@@ -464,8 +468,6 @@ private:
     mutable DataTypeCustomNamePtr custom_name;
     mutable DataTypeCustomTextSerializationPtr custom_text_serialization;
 
-    static String getFileNameForStreamImpl(String stream_name, const SubstreamPath & path);
-
 public:
     const IDataTypeCustomName * getCustomName() const { return custom_name.get(); }
 };

src/Storages/ColumnsDescription.cpp

@@ -185,7 +185,7 @@ void ColumnsDescription::add(ColumnDescription column, const String & after_colu
         insert_it = range.second;
     }
 
-    addSubcolumns(NameAndTypePair(column.name, column.type));
+    addSubcolumns(column.name, column.type);
     columns.get<0>().insert(insert_it, std::move(column));
 }
 
@@ -519,12 +519,13 @@ ColumnsDescription ColumnsDescription::parse(const String & str)
     return result;
 }
 
-void ColumnsDescription::addSubcolumns(NameAndTypePair storage_column)
+void ColumnsDescription::addSubcolumns(const String & storage_name, const DataTypePtr & storage_type)
 {
-    for (const auto & subcolumn_name : storage_column.type->getSubcolumnNames())
+    for (const auto & subcolumn_name : storage_type->getSubcolumnNames())
     {
-        auto subcolumn = NameAndTypePair(storage_column.name, subcolumn_name,
-            storage_column.type, storage_column.type->getSubcolumnType(subcolumn_name));
+        std::cerr << "storage_name: " << storage_name << ", subcolumn_name: " << subcolumn_name << "\n";
+        auto subcolumn = NameAndTypePair(storage_name, subcolumn_name,
+            storage_type, storage_type->getSubcolumnType(subcolumn_name));
 
         if (has(subcolumn.name))
             throw Exception(ErrorCodes::ILLEGAL_COLUMN,

src/Storages/ColumnsDescription.h

@@ -147,7 +147,7 @@ private:
     SubcolumnsContainer subcolumns;
 
     void modifyColumnOrder(const String & column_name, const String & after_column, bool first);
-    void addSubcolumns(NameAndTypePair storage_column);
+    void addSubcolumns(const String & storage_name, const DataTypePtr & storage_type);
 };
 
 /// Validate default expressions and corresponding types compatibility, i.e.

src/Storages/MergeTree/IMergeTreeDataPart.cpp

@@ -191,6 +191,11 @@ std::optional<size_t> IMergeTreeDataPart::getColumnPosition(const String & colum
     return it->second;
 }
 
+std::optional<size_t> IMergeTreeDataPart::getColumnPosition(const NameAndTypePair & column) const
+{
+    return getColumnPosition(column.getStorageName());
+}
+
 DayNum IMergeTreeDataPart::getMinDate() const
 {
     if (storage.minmax_idx_date_column_pos != -1 && minmax_idx.initialized)

src/Storages/MergeTree/IMergeTreeDataPart.h

@@ -142,6 +142,7 @@ public:
     /// take place, you must take original name of column for this part from
     /// storage and pass it to this method.
     std::optional<size_t> getColumnPosition(const String & column_name) const;
+    std::optional<size_t> getColumnPosition(const NameAndTypePair & column) const;
 
     /// Returns the name of a column with minimum compressed size (as returned by getColumnSize()).
     /// If no checksums are present returns the name of the first physically existing column.

src/Storages/MergeTree/IMergeTreeReader.cpp

@@ -265,7 +265,7 @@ IMergeTreeReader::ColumnPosition IMergeTreeReader::findColumnForOffsets(const St
     {
         if (typeid_cast<const DataTypeArray *>(part_column.type.get()))
         {
-            auto position = data_part->getColumnPosition(part_column.name);
+            auto position = data_part->getColumnPosition(part_column);
             if (position && Nested::extractTableName(part_column.name) == table_name)
                 return position;
         }

src/Storages/MergeTree/MergeTreeReaderCompact.cpp

@@ -53,14 +53,14 @@ MergeTreeReaderCompact::MergeTreeReaderCompact(
         auto name_and_type = columns.begin();
         for (size_t i = 0; i < columns_num; ++i, ++name_and_type)
         {
-            const auto & [name, type] = getColumnFromPart(*name_and_type);
-            auto position = data_part->getColumnPosition(name);
+            auto column_from_part = getColumnFromPart(*name_and_type);
+            auto position = data_part->getColumnPosition(column_from_part);
 
-            if (!position && typeid_cast<const DataTypeArray *>(type.get()))
+            if (!position && typeid_cast<const DataTypeArray *>(column_from_part.type.get()))
             {
                 /// If array of Nested column is missing in part,
                 /// we have to read its offsets if they exist.
-                position = findColumnForOffsets(name);
+                position = findColumnForOffsets(column_from_part.name);
                 read_only_offsets[i] = (position != std::nullopt);
             }
 
@@ -149,14 +149,14 @@ size_t MergeTreeReaderCompact::readRows(size_t from_mark, bool continue_reading,
             if (!res_columns[pos])
                 continue;
 
-            auto [name, type] = getColumnFromPart(*name_and_type);
+            auto column_from_part = getColumnFromPart(*name_and_type);
             auto & column = mutable_columns[pos];
 
             try
             {
                 size_t column_size_before_reading = column->size();
 
-                readData(name, *column, *type, from_mark, *column_positions[pos], rows_to_read, read_only_offsets[pos]);
+                readData(column_from_part, *column, from_mark, *column_positions[pos], rows_to_read, read_only_offsets[pos]);
 
                 size_t read_rows_in_column = column->size() - column_size_before_reading;
 
@@ -170,7 +170,7 @@ size_t MergeTreeReaderCompact::readRows(size_t from_mark, bool continue_reading,
                     storage.reportBrokenPart(data_part->name);
 
                 /// Better diagnostics.
-                e.addMessage("(while reading column " + name + ")");
+                e.addMessage("(while reading column " + column_from_part.name + ")");
                 throw;
             }
             catch (...)
@@ -199,9 +199,11 @@ size_t MergeTreeReaderCompact::readRows(size_t from_mark, bool continue_reading,
 }
 
 void MergeTreeReaderCompact::readData(
-    const String & name, IColumn & column, const IDataType & type,
+    const NameAndTypePair & name_and_type, IColumn & column,
     size_t from_mark, size_t column_position, size_t rows_to_read, bool only_offsets)
 {
+    const auto & [name, type] = name_and_type;
+
     if (!isContinuousReading(from_mark, column_position))
         seekToMark(from_mark, column_position);
 
@@ -213,14 +215,29 @@ void MergeTreeReaderCompact::readData(
         return data_buffer;
     };
 
+    IDataType::DeserializeBinaryBulkStatePtr state;
     IDataType::DeserializeBinaryBulkSettings deserialize_settings;
     deserialize_settings.getter = buffer_getter;
     deserialize_settings.avg_value_size_hint = avg_value_size_hints[name];
     deserialize_settings.position_independent_encoding = true;
 
-    IDataType::DeserializeBinaryBulkStatePtr state;
-    type.deserializeBinaryBulkStatePrefix(deserialize_settings, state);
-    type.deserializeBinaryBulkWithMultipleStreams(column, rows_to_read, deserialize_settings, state);
+    if (name_and_type.isSubcolumn())
+    {
+        const auto & storage_type = name_and_type.getStorageType();
+        auto temp_column = storage_type->createColumn();
+
+        storage_type->deserializeBinaryBulkStatePrefix(deserialize_settings, state);
+        storage_type->deserializeBinaryBulkWithMultipleStreams(*temp_column, rows_to_read, deserialize_settings, state);
+
+        auto subcolumn = storage_type->getSubcolumn(name_and_type.getSubcolumnName(), *temp_column);
+        column.insertRangeFrom(*subcolumn, 0, subcolumn->size());
+    }
+    else
+    {
+        deserialize_settings.position_independent_encoding = true;
+        type->deserializeBinaryBulkStatePrefix(deserialize_settings, state);
+        type->deserializeBinaryBulkWithMultipleStreams(column, rows_to_read, deserialize_settings, state);
+    }
 
     /// The buffer is left in inconsistent state after reading single offsets
     if (only_offsets)

src/Storages/MergeTree/MergeTreeReaderCompact.h

@@ -56,7 +56,7 @@ private:
 
     void seekToMark(size_t row_index, size_t column_index);
 
-    void readData(const String & name, IColumn & column, const IDataType & type,
+    void readData(const NameAndTypePair & name_and_type, IColumn & column,
         size_t from_mark, size_t column_position, size_t rows_to_read, bool only_offsets = false);
 
     /// Returns maximal value of granule size in compressed file from @mark_ranges.

tests/queries/0_stateless/001475_read_subcolumns_2.sql

@@ -0,0 +1,48 @@
+DROP TABLE IF EXISTS subcolumns;
+
+CREATE TABLE subcolumns
+(
+    t Tuple
+    (
+        a Array(Nullable(UInt32)),
+        u UInt32,
+        s Nullable(String)
+    ),
+    arr Array(Nullable(String)),
+    arr2 Array(Array(LowCardinality(Nullable(String)))),
+    lc LowCardinality(String),
+    nested Nested(col1 String, col2 Nullable(UInt32))
+) 
+ENGINE = MergeTree order by tuple() SETTINGS min_bytes_for_wide_part = '10M';
+
+INSERT INTO subcolumns VALUES (([1, NULL], 2, 'a'), ['foo', NULL, 'bar'], [['123'], ['456', '789']], 'qqqq', ['zzz', 'xxx'], [42, 43]);
+SELECT * FROM subcolumns;
+SELECT t.a, t.u, t.s, nested.col1, nested.col2, lc FROM subcolumns;
+SELECT t.a.size0, t.a.null, t.u, t.s, t.s.null FROM subcolumns;
+-- SELECT arr2, arr2.size0, arr2.size1, arr2.null FROM subcolumns;
+-- SELECT nested.col1, nested.col2, nested.col1.size0, nested.col2.size0, nested.col2.null FROM subcolumns;
+SELECT sumArray(arr.null), sum(arr.size0) FROM subcolumns;
+DROP TABLE IF EXISTS subcolumns;
+
+CREATE TABLE subcolumns
+(
+    t Tuple
+    (
+        a Array(Nullable(UInt32)),
+        u UInt32,
+        s Nullable(String)
+    ),
+    arr Array(Nullable(String)),
+    arr2 Array(Array(LowCardinality(Nullable(String)))),
+    lc LowCardinality(String),
+    nested Nested(col1 String, col2 Nullable(UInt32))
+) 
+ENGINE = MergeTree order by tuple() SETTINGS min_bytes_for_wide_part = 0;
+
+INSERT INTO subcolumns VALUES (([1, NULL], 2, 'a'), ['foo', NULL, 'bar'], [['123'], ['456', '789']], 'qqqq', ['zzz', 'xxx'], [42, 43]);
+SELECT * FROM subcolumns;
+SELECT t.a, t.u, t.s, nested.col1, nested.col2, lc FROM subcolumns;
+SELECT t.a.size0, t.a.null, t.u, t.s, t.s.null FROM subcolumns;
+-- SELECT arr2, arr2.size0, arr2.size1, arr2.null FROM subcolumns;
+-- SELECT nested.col1, nested.col2, nested.col1.size0, nested.col2.size0, nested.col2.null FROM subcolumns;
+SELECT sumArray(arr.null), sum(arr.size0) FROM subcolumns;

tests/queries/0_stateless/001475_read_subcolumns_storages.sh

@@ -0,0 +1,23 @@
+#!/usr/bin/env bash
+
+CURDIR=$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)
+. "$CURDIR"/../shell_config.sh
+
+set -e
+
+create_query="CREATE TABLE subcolumns(n Nullable(UInt32), a1 Array(UInt32),\
+    a2 Array(Array(Array(UInt32))), a3 Array(Nullable(UInt32)), t Tuple(s String, v UInt32))"
+
+declare -a ENGINES=("Log" "StripeLog" "TinyLog" "Memory" \
+    "MergeTree ORDER BY tuple() SETTINGS min_bytes_for_compact_part='10M'"
+    "MergeTree ORDER BY tuple() SETTINGS min_bytes_for_wide_part='10M'"
+    "MergeTree ORDER BY tuple() SETTINGS min_bytes_for_wide_part=0")
+
+for engine in "${ENGINES[@]}"; do
+    echo $engine
+    $CLICKHOUSE_CLIENT --query "DROP TABLE IF EXISTS subcolumns"
+    $CLICKHOUSE_CLIENT --query "$create_query ENGINE = $engine"
+    $CLICKHOUSE_CLIENT --query "INSERT INTO subcolumns VALUES (100, [1, 2, 3], [[[1, 2], [], [4]], [[5, 6], [7, 8]], [[]]], [1, NULL, 2], ('foo', 200))"
+    $CLICKHOUSE_CLIENT --query "SELECT * FROM subcolumns"
+    $CLICKHOUSE_CLIENT --query "SELECT n, n.null, a1, a1.size0, a2, a2.size0, a2.size1, a2.size2, a3, a3.size0, a3.null, t, t.s, t.v FROM subcolumns"
+done