From 49a129c829daa0eef57ce05664a240be39bb165a Mon Sep 17 00:00:00 2001
From: Michael Kolupaev <mkolupaev@yandex-team.ru>
Date: Tue, 3 Dec 2013 10:19:57 +0000
Subject: [PATCH] ClickHouse: added toFixedString function. [#METR-9091]

---
 .../DB/Functions/FunctionsConversion.h        | 100 ++++++++++++++++++
 dbms/src/Functions/FunctionFactory.cpp        |   1 +
 2 files changed, 101 insertions(+)

diff --git a/dbms/include/DB/Functions/FunctionsConversion.h b/dbms/include/DB/Functions/FunctionsConversion.h
index 76cd11c1a3d..af5391d956d 100644
--- a/dbms/include/DB/Functions/FunctionsConversion.h
+++ b/dbms/include/DB/Functions/FunctionsConversion.h
@@ -11,6 +11,7 @@
 #include <DB/Columns/ColumnFixedString.h>
 #include <DB/Columns/ColumnConst.h>
 #include <DB/Functions/IFunction.h>
+#include <Poco/NumberFormatter.h>
 
 
 namespace DB
@@ -307,6 +308,105 @@ public:
 };
 
 
+/** Преобразование в строку фиксированной длины реализовано только из строк.
+  */
+class FunctionToFixedString : public IFunction
+{
+public:
+	/// Получить имя функции.
+	String getName() const
+	{
+		return "toFixedString";
+	}
+
+	/** Получить тип результата по типам аргументов и значениям константных аргументов.
+	  * Если функция неприменима для данных аргументов - кинуть исключение.
+	  * Для неконстантных столбцов arguments[i].column=NULL.
+	  */
+	void getReturnTypeAndPrerequisites(const ColumnsWithNameAndType & arguments,
+												DataTypePtr & out_return_type,
+												ExpressionActions::Actions & out_prerequisites)
+	{
+		if (arguments.size() != 2)
+			throw Exception("Number of arguments for function " + getName() + " doesn't match: passed "
+				+ toString(arguments.size()) + ", should be 1.",
+				ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH);
+		if (!arguments[1].column)
+			throw Exception("Second argument for function " + getName() + " must be constant", ErrorCodes::ILLEGAL_COLUMN);
+		if (!dynamic_cast<const DataTypeString *>(&*arguments[0].type))
+			throw Exception(getName() + " is only implemented for type String", ErrorCodes::NOT_IMPLEMENTED);
+
+		size_t n = getSize(arguments[1]);
+
+		out_return_type = new DataTypeFixedString(n);
+	}
+
+	/// Выполнить функцию над блоком.
+	void execute(Block & block, const ColumnNumbers & arguments, size_t result)
+	{
+		ColumnPtr column = block.getByPosition(arguments[0]).column;
+		size_t n = getSize(block.getByPosition(arguments[1]));
+
+		if (const ColumnConstString * column_const = dynamic_cast<const ColumnConstString *>(&*column))
+		{
+			if (column_const->getData().size() > n)
+				throw Exception("String too long for type FixedString(" + Poco::NumberFormatter::format(n) + ")",
+					ErrorCodes::TOO_LARGE_STRING_SIZE);
+			block.getByPosition(result).column = new ColumnConst<String>(column_const->size(), column_const->getData(), new DataTypeFixedString(n));
+		}
+		else if(const ColumnString * column_string = dynamic_cast<const ColumnString *>(&*column))
+		{
+			ColumnFixedString * column_fixed = new ColumnFixedString(n);
+			ColumnPtr result_ptr = column_fixed;
+			ColumnFixedString::Chars_t & out_chars = column_fixed->getChars();
+			const ColumnString::Chars_t & in_chars = column_string->getChars();
+			const ColumnString::Offsets_t & in_offsets = column_string->getOffsets();
+			out_chars.resize_fill(in_offsets.size() * n);
+			for (size_t i = 0; i < in_offsets.size(); ++i)
+			{
+				size_t off = i ? in_offsets[i - 1] : 0;
+				size_t len = in_offsets[i] - off - 1;
+				if (len > n)
+					throw Exception("String too long for type FixedString(" + Poco::NumberFormatter::format(n) + ")",
+						ErrorCodes::TOO_LARGE_STRING_SIZE);
+				memcpy(&out_chars[i * n], &in_chars[off], len);
+			}
+			block.getByPosition(result).column = result_ptr;
+		}
+		else
+			throw Exception("Unexpected column: " + column->getName(), ErrorCodes::ILLEGAL_COLUMN);
+	}
+
+private:
+	template <typename T>
+	bool getSizeTyped(const ColumnWithNameAndType & column, size_t & out_size)
+	{
+		if (!dynamic_cast<const typename DataTypeFromFieldType<T>::Type *>(&*column.type))
+			return false;
+		const ColumnConst<T> * column_const = dynamic_cast<const ColumnConst<T> *>(&*column.column);
+		if (!column_const)
+			throw Exception("Unexpected type of column for FixedString length: " + column.column->getName(), ErrorCodes::ILLEGAL_COLUMN);
+		out_size = static_cast<size_t>(column_const->getData());
+		return true;
+	}
+
+	size_t getSize(const ColumnWithNameAndType & column)
+	{
+		size_t res;
+		if (getSizeTyped<UInt8>(column, res) ||
+			getSizeTyped<UInt16>(column, res) ||
+			getSizeTyped<UInt32>(column, res) ||
+			getSizeTyped<UInt64>(column, res) ||
+			getSizeTyped< Int8 >(column, res) ||
+			getSizeTyped< Int16>(column, res) ||
+			getSizeTyped< Int32>(column, res) ||
+			getSizeTyped< Int64>(column, res))
+			return res;
+		throw Exception("Length of FixedString must be integer; got " + column.type->getName(), ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT);
+	}
+};
+
+
 struct NameToUInt8 			{ static const char * get() { return "toUInt8"; } };
 struct NameToUInt16 		{ static const char * get() { return "toUInt16"; } };
 struct NameToUInt32 		{ static const char * get() { return "toUInt32"; } };
diff --git a/dbms/src/Functions/FunctionFactory.cpp b/dbms/src/Functions/FunctionFactory.cpp
index 67721b1b05e..a0646b7515f 100644
--- a/dbms/src/Functions/FunctionFactory.cpp
+++ b/dbms/src/Functions/FunctionFactory.cpp
@@ -92,6 +92,7 @@ FunctionPtr FunctionFactory::get(
 	else if (name == "toDate")						return new FunctionToDate;
 	else if (name == "toDateTime")					return new FunctionToDateTime;
 	else if (name == "toString")					return new FunctionToString;
+	else if (name == "toFixedString")				return new FunctionToFixedString;
 
 	else if (name == "reinterpretAsUInt8")			return new FunctionReinterpretAsUInt8;
 	else if (name == "reinterpretAsUInt16")		return new FunctionReinterpretAsUInt16;