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105 lines
2.5 KiB
C++
105 lines
2.5 KiB
C++
#pragma once
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#include <DB/Storages/IStorage.h>
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#include <DB/Parsers/TablePropertiesQueriesASTs.h>
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#include <DB/Parsers/ASTIdentifier.h>
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#include <DB/Interpreters/Context.h>
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#include <DB/DataStreams/OneBlockInputStream.h>
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#include <DB/DataStreams/BlockIO.h>
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#include <DB/DataStreams/copyData.h>
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#include <DB/DataTypes/DataTypesNumberFixed.h>
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#include <DB/DataTypes/DataTypeString.h>
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#include <DB/Columns/ColumnString.h>
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namespace DB
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{
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/** Вернуть названия и типы столбцов указанной таблицы.
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*/
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class InterpreterDescribeQuery
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{
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public:
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InterpreterDescribeQuery(ASTPtr query_ptr_, Context & context_)
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: query_ptr(query_ptr_), context(context_) {}
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BlockIO execute()
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{
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BlockIO res;
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res.in = executeImpl();
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res.in_sample = getSampleBlock();
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return res;
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}
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BlockInputStreamPtr executeAndFormat(WriteBuffer & buf)
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{
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Block sample = getSampleBlock();
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ASTPtr format_ast = dynamic_cast<ASTDescribeQuery &>(*query_ptr).format;
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String format_name = format_ast ? dynamic_cast<ASTIdentifier &>(*format_ast).name : "TabSeparated";
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BlockInputStreamPtr in = executeImpl();
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BlockOutputStreamPtr out = context.getFormatFactory().getOutput(format_name, buf, sample);
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copyData(*in, *out);
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return in;
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}
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private:
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ASTPtr query_ptr;
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Context context;
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Block getSampleBlock()
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{
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Block block;
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ColumnWithNameAndType col;
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col.name = "name";
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col.type = new DataTypeString;
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block.insert(col);
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col.name = "type";
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block.insert(col);
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return block;
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}
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BlockInputStreamPtr executeImpl()
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{
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const ASTDescribeQuery & ast = dynamic_cast<const ASTDescribeQuery &>(*query_ptr);
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NamesAndTypesList columns;
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{
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Poco::ScopedLock<Poco::Mutex> lock(context.getMutex());
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if (!context.isTableExist(ast.database, ast.table))
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throw Exception("Table " + (ast.database.empty() ? "" : ast.database + ".") + ast.table + " doesn't exist", ErrorCodes::UNKNOWN_TABLE);
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columns = context.getTable(ast.database, ast.table)->getColumnsList();
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}
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ColumnString * name_column = new ColumnString;
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ColumnString * type_column = new ColumnString;
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Block block;
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block.insert(ColumnWithNameAndType(name_column, new DataTypeString, "name"));
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block.insert(ColumnWithNameAndType(type_column, new DataTypeString, "type"));
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for (NamesAndTypesList::iterator it = columns.begin(); it != columns.end(); ++it)
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{
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name_column->insert(it->first);
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type_column->insert(it->second->getName());
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}
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return new OneBlockInputStream(block);
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}
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};
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}
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