ClickHouse/dbms/include/DB/Interpreters/InterpreterShowCreateQuery.h

#pragma once

#include <DB/Storages/IStorage.h>
#include <DB/Parsers/TablePropertiesQueriesASTs.h>
#include <DB/Parsers/ASTIdentifier.h>
#include <DB/Parsers/formatAST.h>
#include <DB/Interpreters/Context.h>
#include <DB/DataStreams/OneBlockInputStream.h>
#include <DB/DataStreams/BlockIO.h>
#include <DB/DataStreams/copyData.h>
#include <DB/DataTypes/DataTypesNumberFixed.h>
#include <DB/DataTypes/DataTypeString.h>


namespace DB
{
	
	
/** Вернуть одну строку с одним столбцом statement типа String с текстом запроса, создающего указанную таблицу.
	*/
class InterpreterShowCreateQuery
{
public:
	InterpreterShowCreateQuery(ASTPtr query_ptr_, Context & context_)
		: query_ptr(query_ptr_), context(context_) {}
	
	BlockIO execute()
	{
		BlockIO res;
		res.in = executeImpl();
		res.in_sample = getSampleBlock();
		
		return res;
	}
	
	BlockInputStreamPtr executeAndFormat(WriteBuffer & buf)
	{
		Block sample = getSampleBlock();
		ASTPtr format_ast = dynamic_cast<ASTShowCreateQuery &>(*query_ptr).format;
		String format_name = format_ast ? dynamic_cast<ASTIdentifier &>(*format_ast).name : context.getDefaultFormat();
		
		BlockInputStreamPtr in = executeImpl();
		BlockOutputStreamPtr out = context.getFormatFactory().getOutput(format_name, buf, sample);
		
		copyData(*in, *out);
		
		return in;
	}
	
private:
	ASTPtr query_ptr;
	Context context;
	
	Block getSampleBlock()
	{
		ColumnWithNameAndType col;
		col.name = "statement";
		col.type = new DataTypeString;
		col.column = col.type->createColumn();
		
		Block block;
		block.insert(col);
		
		return block;
	}
	
	BlockInputStreamPtr executeImpl()
	{
		const ASTShowCreateQuery & ast = dynamic_cast<const ASTShowCreateQuery &>(*query_ptr);
		
		String res;
		
		{
			Poco::ScopedLock<Poco::Mutex> lock(context.getMutex());
		
			if (!context.isTableExist(ast.database, ast.table))
				throw Exception("Table " + (ast.database.empty() ? "" : ast.database + ".") + ast.table + " doesn't exist", ErrorCodes::UNKNOWN_TABLE);
			
			std::stringstream stream;
			formatAST(*context.getCreateQuery(ast.database, ast.table), stream, 0, false, true);
			res = stream.str();
		}
		
		ColumnWithNameAndType col;
		col.name = "statement";
		col.type = new DataTypeString;
		col.column = new ColumnConstString(1, res);
		
		Block block;
		block.insert(col);
		
		return new OneBlockInputStream(block);
	}
};
	
	
}