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https://github.com/ClickHouse/ClickHouse.git
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86 lines
1.9 KiB
C++
86 lines
1.9 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/FormatFactory.h>
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#include <DB/DataStreams/copyData.h>
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#include <DB/DataTypes/DataTypesNumberFixed.h>
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namespace DB
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{
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/** Проверить, существует ли таблица. Вернуть одну строку с одним столбцом result типа UInt8 со значением 0 или 1.
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*/
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class InterpreterExistsQuery
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{
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public:
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InterpreterExistsQuery(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 = typeid_cast<ASTExistsQuery &>(*query_ptr).format;
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String format_name = format_ast ? typeid_cast<ASTIdentifier &>(*format_ast).name : context.getDefaultFormat();
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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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ColumnWithNameAndType col;
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col.name = "result";
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col.type = new DataTypeUInt8;
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col.column = col.type->createColumn();
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Block block;
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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 ASTExistsQuery & ast = typeid_cast<const ASTExistsQuery &>(*query_ptr);
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bool res = context.isTableExist(ast.database, ast.table);
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ColumnWithNameAndType col;
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col.name = "result";
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col.type = new DataTypeUInt8;
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col.column = new ColumnConstUInt8(1, res);
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Block block;
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block.insert(col);
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return new OneBlockInputStream(block);
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}
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};
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}
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