ClickHouse/src/Parsers/ASTSampleRatio.h

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#pragma once
#include <Parsers/IAST.h>
namespace DB
{
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/** Sampling factor in the form 0.1 or 1/10.
* It's important to save it as a rational number without converting it to IEEE-754.
*/
class ASTSampleRatio : public IAST
{
public:
#ifdef __SIZEOF_INT128__
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using BigNum = __uint128_t; /// Must contain the result of multiplying two UInt64.
#else
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#warning "No uint128_t type. Sampling ratios cannot work correctly."
using BigNum = uint64_t;
#endif
struct Rational
{
BigNum numerator = 0;
BigNum denominator = 1;
};
Rational ratio;
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ASTSampleRatio(Rational & ratio_) : ratio(ratio_) {}
String getID(char delim) const override { return "SampleRatio" + (delim + toString(ratio)); }
ASTPtr clone() const override { return std::make_shared<ASTSampleRatio>(*this); }
static String toString(BigNum num);
static String toString(Rational ratio);
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void formatImpl(const FormatSettings & settings, FormatState &, FormatStateStacked) const override
{
settings.ostr << toString(ratio);
}
};
}