ClickHouse/dbms/include/DB/Interpreters/InterpreterExistsQuery.h
2013-05-22 14:57:43 +00:00

84 lines
1.8 KiB
C++
Raw Blame History

This file contains ambiguous Unicode characters

This file contains Unicode characters that might be confused with other characters. If you think that this is intentional, you can safely ignore this warning. Use the Escape button to reveal them.

#pragma once
#include <DB/Storages/IStorage.h>
#include <DB/Parsers/TablePropertiesQueriesASTs.h>
#include <DB/Parsers/ASTIdentifier.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>
namespace DB
{
/** Проверить, существует ли таблица. Вернуть одну строку с одним столбцом result типа UInt8 со значением 0 или 1.
*/
class InterpreterExistsQuery
{
public:
InterpreterExistsQuery(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<ASTExistsQuery &>(*query_ptr).format;
String format_name = format_ast ? dynamic_cast<ASTIdentifier &>(*format_ast).name : "TabSeparated";
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 = "result";
col.type = new DataTypeUInt8;
Block block;
block.insert(col);
return block;
}
BlockInputStreamPtr executeImpl()
{
const ASTExistsQuery & ast = dynamic_cast<const ASTExistsQuery &>(*query_ptr);
bool res = context.isTableExist(ast.database, ast.table);
ColumnWithNameAndType col;
col.name = "result";
col.type = new DataTypeUInt8;
col.column = new ColumnConstUInt8(1, res);
Block block;
block.insert(col);
return new OneBlockInputStream(block);
}
};
}