ClickHouse/src/Processors/Formats/IRowOutputFormat.h

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#pragma once
#include <Formats/FormatFactory.h>
#include <Processors/Formats/IOutputFormat.h>
#include <string>
namespace DB
{
struct RowOutputFormatParams
{
using WriteCallback = std::function<void(const Columns & columns,size_t row)>;
// Callback used to indicate that another row is written.
WriteCallback callback;
};
class WriteBuffer;
/** Output format that writes data row by row.
*/
class IRowOutputFormat : public IOutputFormat
{
protected:
DataTypes types;
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bool first_row = true;
void consume(Chunk chunk) override;
void consumeTotals(Chunk chunk) override;
void consumeExtremes(Chunk chunk) override;
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void finalize() override;
public:
using Params = RowOutputFormatParams;
IRowOutputFormat(const Block & header, WriteBuffer & out_, const Params & params_)
: IOutputFormat(header, out_), types(header.getDataTypes()), params(params_)
{
}
/** Write a row.
* Default implementation calls methods to write single values and delimiters
* (except delimiter between rows (writeRowBetweenDelimiter())).
*/
virtual void write(const Columns & columns, size_t row_num);
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virtual void writeMinExtreme(const Columns & columns, size_t row_num);
virtual void writeMaxExtreme(const Columns & columns, size_t row_num);
virtual void writeTotals(const Columns & columns, size_t row_num);
/** Write single value. */
virtual void writeField(const IColumn & column, const IDataType & type, size_t row_num) = 0;
/** Write delimiter. */
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virtual void writeFieldDelimiter() {} /// delimiter between values
virtual void writeRowStartDelimiter() {} /// delimiter before each row
virtual void writeRowEndDelimiter() {} /// delimiter after each row
virtual void writeRowBetweenDelimiter() {} /// delimiter between rows
virtual void writePrefix() {} /// delimiter before resultset
virtual void writeSuffix() {} /// delimiter after resultset
virtual void writeBeforeTotals() {}
virtual void writeAfterTotals() {}
virtual void writeBeforeExtremes() {}
virtual void writeAfterExtremes() {}
virtual void writeLastSuffix() {} /// Write something after resultset, totals end extremes.
private:
bool prefix_written = false;
bool suffix_written = false;
Params params;
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void writePrefixIfNot()
{
if (!prefix_written)
writePrefix();
prefix_written = true;
}
void writeSuffixIfNot()
{
if (!suffix_written)
writeSuffix();
suffix_written = true;
}
};
}