Support insertion into LowCardinality from old native clients.

dbms/programs/server/TCPHandler.cpp

@@ -30,6 +30,7 @@
 #include <Storages/StorageMemory.h>
 #include <Storages/StorageReplicatedMergeTree.h>
 #include <Core/ExternalTable.h>
+#include <DataTypes/DataTypeLowCardinality.h>
 
 #include "TCPHandler.h"
 
@@ -361,6 +362,17 @@ 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);
 
     readData(global_settings);
@@ -743,8 +755,13 @@ void TCPHandler::initBlockInput()
         else
             state.maybe_compressed_in = in;
 
+        Block header;
+        if (state.io.out)
+            header = state.io.out->getHeader();
+
         state.block_in = std::make_shared<NativeBlockInputStream>(
             *state.maybe_compressed_in,
+            header,
             client_revision);
     }
 }

dbms/src/Columns/ColumnLowCardinality.cpp

@@ -163,7 +163,7 @@ void ColumnLowCardinality::insertRangeFrom(const IColumn & src, size_t start, si
     auto * low_cardinality_src = typeid_cast<const ColumnLowCardinality *>(&src);
 
     if (!low_cardinality_src)
-        throw Exception("Expected ColumnLowCardinality, got" + src.getName(), ErrorCodes::ILLEGAL_COLUMN);
+        throw Exception("Expected ColumnLowCardinality, got " + src.getName(), ErrorCodes::ILLEGAL_COLUMN);
 
     if (&low_cardinality_src->getDictionary() == &getDictionary())
     {

dbms/src/Core/Defines.h

@@ -52,6 +52,8 @@
 /// (keys will be placed in different buckets and result will not be fully aggregated).
 #define DBMS_MIN_REVISION_WITH_CURRENT_AGGREGATION_VARIANT_SELECTION_METHOD 54408
 
+#define DBMS_MIN_REVISION_WITH_LOW_CARDINALITY_TYPE 54405
+
 /// Version of ClickHouse TCP protocol. Set to git tag with latest protocol change.
 #define DBMS_TCP_PROTOCOL_VERSION 54226
 

dbms/src/DataStreams/NativeBlockInputStream.cpp

@@ -9,6 +9,7 @@
 #include <ext/range.h>
 
 #include <DataStreams/NativeBlockInputStream.h>
+#include <DataTypes/DataTypeLowCardinality.h>
 
 
 namespace DB
@@ -152,6 +153,9 @@ Block NativeBlockInputStream::readImpl()
 
         column.column = std::move(read_column);
 
+        if (server_revision && server_revision < DBMS_MIN_REVISION_WITH_LOW_CARDINALITY_TYPE)
+            column.column = recursiveLowCardinalityConversion(column.column, column.type, header.getByPosition(i).type);
+
         res.insert(std::move(column));
 
         if (use_index)

dbms/src/DataTypes/DataTypeLowCardinality.h

@@ -164,4 +164,13 @@ class DataTypeLowCardinality : public IDataType
 /// Returns dictionary type if type is DataTypeLowCardinality, type otherwise.
 DataTypePtr removeLowCardinality(const DataTypePtr & type);
 
+/// Remove LowCardinality recursively from all nested types.
+DataTypePtr recursiveRemoveLowCardinality(const DataTypePtr & type);
+
+/// Remove LowCardinality recursively from all nested columns.
+ColumnPtr recursiveRemoveLowCardinality(const ColumnPtr & column);
+
+/// Convert column of type from_type to type to_type by converting nested LowCardinality columns.
+ColumnPtr recursiveLowCardinalityConversion(const ColumnPtr & column, const DataTypePtr & from_type, const DataTypePtr & to_type);
+
 }

dbms/src/DataTypes/DataTypeLowCardinalityHelpers.cpp

@@ -0,0 +1,137 @@
+#include <Columns/ColumnArray.h>
+#include <Columns/ColumnConst.h>
+#include <Columns/ColumnTuple.h>
+#include <Columns/ColumnLowCardinality.h>
+
+#include <DataTypes/DataTypeLowCardinality.h>
+#include <DataTypes/DataTypeArray.h>
+#include <DataTypes/DataTypeTuple.h>
+
+namespace DB
+{
+
+namespace ErrorCodes
+{
+    extern const int ILLEGAL_COLUMN;
+    extern const int TYPE_MISMATCH;
+}
+
+DataTypePtr recursiveRemoveLowCardinality(const DataTypePtr & type)
+{
+    if (!type)
+        return type;
+
+    if (const auto * array_type = typeid_cast<const DataTypeArray *>(type.get()))
+        return std::make_shared<DataTypeArray>(recursiveRemoveLowCardinality(array_type->getNestedType()));
+
+    if (const auto * tuple_type = typeid_cast<const DataTypeTuple *>(type.get()))
+    {
+        DataTypes elements = tuple_type->getElements();
+        for (auto & element : elements)
+            element = recursiveRemoveLowCardinality(element);
+
+        if (tuple_type->haveExplicitNames())
+            return std::make_shared<DataTypeTuple>(elements, tuple_type->getElementNames());
+        else
+            return std::make_shared<DataTypeTuple>(elements);
+    }
+
+    if (const auto * low_cardinality_type = typeid_cast<const DataTypeLowCardinality *>(type.get()))
+        return low_cardinality_type->getDictionaryType();
+
+    return type;
+}
+
+ColumnPtr recursiveRemoveLowCardinality(const ColumnPtr & column)
+{
+    if (!column)
+        return column;
+
+    if (const auto * column_array = typeid_cast<const ColumnArray *>(column.get()))
+        return ColumnArray::create(recursiveRemoveLowCardinality(column_array->getDataPtr()), column_array->getOffsetsPtr());
+
+    if (const auto * column_const = typeid_cast<const ColumnConst *>(column.get()))
+        return ColumnConst::create(recursiveRemoveLowCardinality(column_const->getDataColumnPtr()), column_const->size());
+
+    if (const auto * column_tuple = typeid_cast<const ColumnTuple *>(column.get()))
+    {
+        Columns columns = column_tuple->getColumns();
+        for (auto & element : columns)
+            element = recursiveRemoveLowCardinality(element);
+        return ColumnTuple::create(columns);
+    }
+
+    if (const auto * column_low_cardinality = typeid_cast<const ColumnLowCardinality *>(column.get()))
+        return column_low_cardinality->convertToFullColumn();
+
+    return column;
+}
+
+ColumnPtr recursiveLowCardinalityConversion(const ColumnPtr & column, const DataTypePtr & from_type, const DataTypePtr & to_type)
+{
+    if (from_type->equals(*to_type))
+        return column;
+
+    if (const auto * column_const = typeid_cast<const ColumnConst *>(column.get()))
+        return ColumnConst::create(recursiveLowCardinalityConversion(column_const->getDataColumnPtr(), from_type, to_type),
+                                   column_const->size());
+
+    if (const auto * low_cardinality_type = typeid_cast<const DataTypeLowCardinality *>(from_type.get()))
+    {
+        if (to_type->equals(*low_cardinality_type->getDictionaryType()))
+            return column->convertToFullColumnIfLowCardinality();
+    }
+
+    if (const auto * low_cardinality_type = typeid_cast<const DataTypeLowCardinality *>(to_type.get()))
+    {
+        if (from_type->equals(*low_cardinality_type->getDictionaryType()))
+        {
+            auto col = low_cardinality_type->createColumn();
+            static_cast<ColumnLowCardinality &>(*col).insertRangeFromFullColumn(*column, 0, column->size());
+            return std::move(col);
+        }
+    }
+
+    if (const auto * from_array_type = typeid_cast<const DataTypeArray *>(from_type.get()))
+    {
+        if (const auto * to_array_type = typeid_cast<const DataTypeArray *>(to_type.get()))
+        {
+            const auto * column_array = typeid_cast<const ColumnArray *>(column.get());
+            if (!column_array)
+                throw Exception("Unexpected column " + column->getName() + " for type " + from_type->getName(),
+                                ErrorCodes::ILLEGAL_COLUMN);
+
+            auto & nested_from = from_array_type->getNestedType();
+            auto & nested_to = to_array_type->getNestedType();
+
+            return ColumnArray::create(
+                    recursiveLowCardinalityConversion(column_array->getDataPtr(), nested_from, nested_to),
+                    column_array->getOffsetsPtr());
+        }
+    }
+
+    if (const auto * from_tuple_type = typeid_cast<const DataTypeTuple *>(from_type.get()))
+    {
+        if (const auto * to_tuple_type = typeid_cast<const DataTypeTuple *>(to_type.get()))
+        {
+            const auto * column_tuple = typeid_cast<const ColumnTuple *>(column.get());
+            if (!column_tuple)
+                throw Exception("Unexpected column " + column->getName() + " for type " + from_type->getName(),
+                                ErrorCodes::ILLEGAL_COLUMN);
+
+            Columns columns = column_tuple->getColumns();
+            auto & from_elements = from_tuple_type->getElements();
+            auto & to_elements = to_tuple_type->getElements();
+            for (size_t i = 0; i < columns.size(); ++i)
+            {
+                auto & element = columns[i];
+                element = recursiveLowCardinalityConversion(element, from_elements.at(i), to_elements.at(i));
+            }
+            return ColumnTuple::create(columns);
+        }
+    }
+
+    throw Exception("Cannot convert: " + from_type->getName() + " to " + to_type->getName(), ErrorCodes::TYPE_MISMATCH);
+}
+
+}

dbms/src/Functions/IFunction.cpp

@@ -103,58 +103,6 @@ void PreparedFunctionImpl::createLowCardinalityResultCache(size_t cache_size)
 }
 
 
-static DataTypePtr recursiveRemoveLowCardinality(const DataTypePtr & type)
-{
-    if (!type)
-        return type;
-
-    if (const auto * array_type = typeid_cast<const DataTypeArray *>(type.get()))
-        return std::make_shared<DataTypeArray>(recursiveRemoveLowCardinality(array_type->getNestedType()));
-
-    if (const auto * tuple_type = typeid_cast<const DataTypeTuple *>(type.get()))
-    {
-        DataTypes elements = tuple_type->getElements();
-        for (auto & element : elements)
-            element = recursiveRemoveLowCardinality(element);
-
-        if (tuple_type->haveExplicitNames())
-            return std::make_shared<DataTypeTuple>(elements, tuple_type->getElementNames());
-        else
-            return std::make_shared<DataTypeTuple>(elements);
-    }
-
-    if (const auto * low_cardinality_type = typeid_cast<const DataTypeLowCardinality *>(type.get()))
-        return low_cardinality_type->getDictionaryType();
-
-    return type;
-}
-
-static ColumnPtr recursiveRemoveLowCardinality(const ColumnPtr & column)
-{
-    if (!column)
-        return column;
-
-    if (const auto * column_array = typeid_cast<const ColumnArray *>(column.get()))
-        return ColumnArray::create(recursiveRemoveLowCardinality(column_array->getDataPtr()), column_array->getOffsetsPtr());
-
-    if (const auto * column_const = typeid_cast<const ColumnConst *>(column.get()))
-        return ColumnConst::create(recursiveRemoveLowCardinality(column_const->getDataColumnPtr()), column_const->size());
-
-    if (const auto * column_tuple = typeid_cast<const ColumnTuple *>(column.get()))
-    {
-        Columns columns = column_tuple->getColumns();
-        for (auto & element : columns)
-            element = recursiveRemoveLowCardinality(element);
-        return ColumnTuple::create(columns);
-    }
-
-    if (const auto * column_low_cardinality = typeid_cast<const ColumnLowCardinality *>(column.get()))
-        return column_low_cardinality->convertToFullColumn();
-
-    return column;
-}
-
-
 ColumnPtr wrapInNullable(const ColumnPtr & src, const Block & block, const ColumnNumbers & args, size_t result, size_t input_rows_count)
 {
     ColumnPtr result_null_map_column;