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87 lines
2.9 KiB
C++
87 lines
2.9 KiB
C++
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#include <DataStreams/ConvertingBlockInputStream.h>
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#include <Interpreters/castColumn.h>
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#include <Columns/ColumnConst.h>
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#include <Parsers/IAST.h>
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namespace DB
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{
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namespace ErrorCodes
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{
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extern const int THERE_IS_NO_COLUMN;
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extern const int BLOCKS_HAVE_DIFFERENT_STRUCTURE;
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}
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ConvertingBlockInputStream::ConvertingBlockInputStream(
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const Context & context_,
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const BlockInputStreamPtr & input,
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const Block & result_header)
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: context(context_), header(result_header), conversion(header.columns())
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{
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children.emplace_back(input);
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Block input_header = input->getHeader();
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size_t num_input_columns = input_header.columns();
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for (size_t result_col_num = 0, num_result_columns = result_header.columns(); result_col_num < num_result_columns; ++result_col_num)
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{
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const auto & res_elem = result_header.getByPosition(result_col_num);
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if (input_header.has(res_elem.name))
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conversion[result_col_num] = input_header.getPositionByName(res_elem.name);
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else if (result_col_num < num_input_columns)
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conversion[result_col_num] = result_col_num;
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else
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throw Exception("Cannot find column " + backQuoteIfNeed(res_elem.name) + " in source stream",
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ErrorCodes::THERE_IS_NO_COLUMN);
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const auto & src_elem = input_header.getByPosition(conversion[result_col_num]);
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/// Check constants.
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if (res_elem.column->isColumnConst())
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{
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if (!src_elem.column->isColumnConst())
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throw Exception("Cannot convert column " + backQuoteIfNeed(res_elem.name)
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+ " because it is non constant in source stream but must be constant in result",
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ErrorCodes::BLOCKS_HAVE_DIFFERENT_STRUCTURE);
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else if (static_cast<const ColumnConst &>(*src_elem.column).getField() != static_cast<const ColumnConst &>(*res_elem.column).getField())
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throw Exception("Cannot convert column " + backQuoteIfNeed(res_elem.name)
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+ " because it is constant but values of constants are different in source and result",
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ErrorCodes::BLOCKS_HAVE_DIFFERENT_STRUCTURE);
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}
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/// Check conversion by dry run CAST function.
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castColumn(src_elem, res_elem.type, context);
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}
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}
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Block ConvertingBlockInputStream::readImpl()
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{
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Block src = children.back()->read();
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if (!src)
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return src;
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Block res = header.cloneEmpty();
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for (size_t res_pos = 0, size = conversion.size(); res_pos < size; ++res_pos)
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{
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const auto & src_elem = src.getByPosition(conversion[res_pos]);
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auto & res_elem = res.getByPosition(res_pos);
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ColumnPtr converted = castColumn(src_elem, res_elem.type, context);
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if (src_elem.column->isColumnConst() && !res_elem.column->isColumnConst())
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converted = converted->convertToFullColumnIfConst();
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res_elem.column = std::move(converted);
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}
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return res;
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}
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}
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