Added low_cardinality_allow_in_native_format setting.

dbms/programs/server/TCPHandler.cpp

@@ -370,19 +370,7 @@ void TCPHandler::processInsertQuery(const Settings & global_settings)
     }
 
     /// Send block to the client - table structure.
-    Block block = state.io.out->getHeader();
-
-    /// Support insert from old clients without low cardinality type.
-    if (client_revision && client_revision < DBMS_MIN_REVISION_WITH_LOW_CARDINALITY_TYPE)
-    {
-        for (auto & col : block)
-        {
-            col.type = recursiveRemoveLowCardinality(col.type);
-            col.column = recursiveRemoveLowCardinality(col.column);
-        }
-    }
-
-    sendData(block);
+    sendData(state.io.out->getHeader());
 
     readData(global_settings);
     state.io.out->writeSuffix();
@@ -399,16 +387,6 @@ void TCPHandler::processOrdinaryQuery()
         {
             Block header = state.io.in->getHeader();
 
-            /// Send data to old clients without low cardinality type.
-            if (client_revision && client_revision < DBMS_MIN_REVISION_WITH_LOW_CARDINALITY_TYPE)
-            {
-                for (auto & column : header)
-                {
-                    column.column = recursiveRemoveLowCardinality(column.column);
-                    column.type = recursiveRemoveLowCardinality(column.type);
-                }
-            }
-
             if (header)
                 sendData(header);
         }
@@ -782,7 +760,8 @@ void TCPHandler::initBlockInput()
         state.block_in = std::make_shared<NativeBlockInputStream>(
             *state.maybe_compressed_in,
             header,
-            client_revision);
+            client_revision,
+            !connection_context.getSettingsRef().low_cardinality_allow_in_native_format);
     }
 }
 
@@ -803,7 +782,8 @@ void TCPHandler::initBlockOutput(const Block & block)
         state.block_out = std::make_shared<NativeBlockOutputStream>(
             *state.maybe_compressed_out,
             client_revision,
-            block.cloneEmpty());
+            block.cloneEmpty(),
+            !connection_context.getSettingsRef().low_cardinality_allow_in_native_format);
     }
 }
 
@@ -815,7 +795,8 @@ void TCPHandler::initLogsBlockOutput(const Block & block)
         state.logs_block_out = std::make_shared<NativeBlockOutputStream>(
             *out,
             client_revision,
-            block.cloneEmpty());
+            block.cloneEmpty(),
+            !connection_context.getSettingsRef().low_cardinality_allow_in_native_format);
     }
 }
 

dbms/src/DataStreams/NativeBlockInputStream.cpp

@@ -29,8 +29,8 @@ NativeBlockInputStream::NativeBlockInputStream(ReadBuffer & istr_, UInt64 server
 {
 }
 
-NativeBlockInputStream::NativeBlockInputStream(ReadBuffer & istr_, const Block & header_, UInt64 server_revision_)
-    : istr(istr_), header(header_), server_revision(server_revision_)
+NativeBlockInputStream::NativeBlockInputStream(ReadBuffer & istr_, const Block & header_, UInt64 server_revision_, bool convert_types_to_low_cardinality_)
+    : istr(istr_), header(header_), server_revision(server_revision_), convert_types_to_low_cardinality(convert_types_to_low_cardinality_)
 {
 }
 
@@ -154,7 +154,8 @@ Block NativeBlockInputStream::readImpl()
         column.column = std::move(read_column);
 
         /// Support insert from old clients without low cardinality type.
-        if (header && server_revision && server_revision < DBMS_MIN_REVISION_WITH_LOW_CARDINALITY_TYPE)
+        bool revision_without_low_cardinality = server_revision && server_revision < DBMS_MIN_REVISION_WITH_LOW_CARDINALITY_TYPE;
+        if (header && (convert_types_to_low_cardinality || revision_without_low_cardinality))
         {
             column.column = recursiveLowCardinalityConversion(column.column, column.type, header.getByPosition(i).type);
             column.type = header.getByPosition(i).type;

dbms/src/DataStreams/NativeBlockInputStream.h

@@ -65,7 +65,7 @@ class NativeBlockInputStream : public IProfilingBlockInputStream
 
     /// For cases when data structure (header) is known in advance.
     /// NOTE We may use header for data validation and/or type conversions. It is not implemented.
-    NativeBlockInputStream(ReadBuffer & istr_, const Block & header_, UInt64 server_revision_);
+    NativeBlockInputStream(ReadBuffer & istr_, const Block & header_, UInt64 server_revision_, bool convert_types_to_low_cardinality_ = false);
 
     /// For cases when we have an index. It allows to skip columns. Only columns specified in the index will be read.
     NativeBlockInputStream(ReadBuffer & istr_, UInt64 server_revision_,
@@ -91,6 +91,8 @@ class NativeBlockInputStream : public IProfilingBlockInputStream
     IndexForNativeFormat::Blocks::const_iterator index_block_end;
     IndexOfBlockForNativeFormat::Columns::const_iterator index_column_it;
 
+    bool convert_types_to_low_cardinality = false;
+
     /// If an index is specified, then `istr` must be CompressedReadBufferFromFile. Unused otherwise.
     CompressedReadBufferFromFile * istr_concrete = nullptr;
 

dbms/src/DataStreams/NativeBlockOutputStream.cpp

@@ -21,10 +21,10 @@ namespace ErrorCodes
 
 
 NativeBlockOutputStream::NativeBlockOutputStream(
-    WriteBuffer & ostr_, UInt64 client_revision_, const Block & header_,
+    WriteBuffer & ostr_, UInt64 client_revision_, const Block & header_, bool remove_low_cardinality_,
     WriteBuffer * index_ostr_, size_t initial_size_of_file_)
     : ostr(ostr_), client_revision(client_revision_), header(header_),
-    index_ostr(index_ostr_), initial_size_of_file(initial_size_of_file_)
+    index_ostr(index_ostr_), initial_size_of_file(initial_size_of_file_), remove_low_cardinality(remove_low_cardinality_)
 {
     if (index_ostr)
     {
@@ -104,7 +104,7 @@ void NativeBlockOutputStream::write(const Block & block)
         ColumnWithTypeAndName column = block.safeGetByPosition(i);
 
         /// Send data to old clients without low cardinality type.
-        if (client_revision && client_revision < DBMS_MIN_REVISION_WITH_LOW_CARDINALITY_TYPE)
+        if (remove_low_cardinality || (client_revision && client_revision < DBMS_MIN_REVISION_WITH_LOW_CARDINALITY_TYPE))
         {
             column.column = recursiveRemoveLowCardinality(column.column);
             column.type = recursiveRemoveLowCardinality(column.type);

dbms/src/DataStreams/NativeBlockOutputStream.h

@@ -23,7 +23,7 @@ class NativeBlockOutputStream : public IBlockOutputStream
     /** If non-zero client_revision is specified, additional block information can be written.
       */
     NativeBlockOutputStream(
-        WriteBuffer & ostr_, UInt64 client_revision_, const Block & header_,
+        WriteBuffer & ostr_, UInt64 client_revision_, const Block & header_, bool remove_low_cardinality_ = false,
         WriteBuffer * index_ostr_ = nullptr, size_t initial_size_of_file_ = 0);
 
     Block getHeader() const override { return header; }
@@ -42,6 +42,8 @@ class NativeBlockOutputStream : public IBlockOutputStream
     size_t initial_size_of_file;    /// The initial size of the data file, if `append` done. Used for the index.
     /// If you need to write index, then `ostr` must be a CompressedWriteBuffer.
     CompressedWriteBuffer * ostr_concrete = nullptr;
+
+    bool remove_low_cardinality;
 };
 
 }

dbms/src/Interpreters/Settings.h

@@ -294,7 +294,7 @@ struct Settings
     M(SettingBool, parallel_view_processing, false, "Enables pushing to attached views concurrently instead of sequentially.") \
     M(SettingBool, enable_debug_queries, false, "Enables debug queries such as AST.") \
     M(SettingBool, enable_unaligned_array_join, false, "Allow ARRAY JOIN with multiple arrays that have different sizes. When this settings is enabled, arrays will be resized to the longest one.") \
-
+    M(SettingBool, low_cardinality_allow_in_native_format, true, "Use LowCardinality type in Native format. Otherwise, convert LowCardinality columns to ordinary for select query, and convert ordinary columns to required LowCardinality for insert query.") \
 
 #define DECLARE(TYPE, NAME, DEFAULT, DESCRIPTION) \
     TYPE NAME {DEFAULT};

dbms/src/Storages/StorageStripeLog.cpp

@@ -139,7 +139,7 @@ class StripeLogBlockOutputStream final : public IBlockOutputStream
         data_out(data_out_compressed, CompressionSettings(CompressionMethod::LZ4), storage.max_compress_block_size),
         index_out_compressed(storage.full_path() + "index.mrk", INDEX_BUFFER_SIZE, O_WRONLY | O_APPEND | O_CREAT),
         index_out(index_out_compressed),
-        block_out(data_out, 0, storage.getSampleBlock(), &index_out, Poco::File(storage.full_path() + "data.bin").getSize())
+        block_out(data_out, 0, storage.getSampleBlock(), false, &index_out, Poco::File(storage.full_path() + "data.bin").getSize())
     {
     }