be/src/exprs/decimal-operators.h

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// to you under the Apache License, Version 2.0 (the
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//
//   http://www.apache.org/licenses/LICENSE-2.0
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#ifndef IMPALA_EXPRS_DECIMAL_OPERATORS_H
#define IMPALA_EXPRS_DECIMAL_OPERATORS_H

#include <stdint.h>

#include "common/global-types.h"
#include "runtime/decimal-value.h"
#include "udf/udf.h"

namespace impala {

using impala_udf::FunctionContext;
using impala_udf::AnyVal;
using impala_udf::BooleanVal;
using impala_udf::TinyIntVal;
using impala_udf::SmallIntVal;
using impala_udf::IntVal;
using impala_udf::BigIntVal;
using impala_udf::FloatVal;
using impala_udf::DoubleVal;
using impala_udf::TimestampVal;
using impala_udf::StringVal;
using impala_udf::DecimalVal;

class Expr;
struct ExprValue;
class TupleRow;

/// Implementation of the decimal operators. These include the cast,
/// arithmetic and binary operators.
class DecimalOperators {
 public:
  static DecimalVal CastToDecimalVal(FunctionContext*, const DecimalVal&);

  static DecimalVal CastToDecimalVal(FunctionContext*, const TinyIntVal&);
  static DecimalVal CastToDecimalVal(FunctionContext*, const SmallIntVal&);
  static DecimalVal CastToDecimalVal(FunctionContext*, const IntVal&);
  static DecimalVal CastToDecimalVal(FunctionContext*, const BigIntVal&);
  static DecimalVal CastToDecimalVal(FunctionContext*, const FloatVal&);
  static DecimalVal CastToDecimalVal(FunctionContext*, const DoubleVal&);
  static DecimalVal CastToDecimalVal(FunctionContext*, const StringVal&);

  static BooleanVal CastToBooleanVal(FunctionContext*, const DecimalVal&);
  static TinyIntVal CastToTinyIntVal(FunctionContext*, const DecimalVal&);
  static SmallIntVal CastToSmallIntVal(FunctionContext*, const DecimalVal&);
  static IntVal CastToIntVal(FunctionContext*, const DecimalVal&);
  static BigIntVal CastToBigIntVal(FunctionContext*, const DecimalVal&);
  static FloatVal CastToFloatVal(FunctionContext*, const DecimalVal&);
  static DoubleVal CastToDoubleVal(FunctionContext*, const DecimalVal&);
  static StringVal CastToStringVal(FunctionContext*, const DecimalVal&);
  static TimestampVal CastToTimestampVal(FunctionContext*, const DecimalVal&);

  static DecimalVal Add_DecimalVal_DecimalVal(
      FunctionContext*, const DecimalVal&, const DecimalVal&);
  static DecimalVal Subtract_DecimalVal_DecimalVal(
      FunctionContext*, const DecimalVal&, const DecimalVal&);
  static DecimalVal Multiply_DecimalVal_DecimalVal(
      FunctionContext*, const DecimalVal&, const DecimalVal&);
  static DecimalVal Divide_DecimalVal_DecimalVal(
      FunctionContext*, const DecimalVal&, const DecimalVal&);
  static DecimalVal Mod_DecimalVal_DecimalVal(
      FunctionContext*, const DecimalVal&, const DecimalVal&);

  static BooleanVal Eq_DecimalVal_DecimalVal(
      FunctionContext*, const DecimalVal&, const DecimalVal&);
  static BooleanVal Ne_DecimalVal_DecimalVal(
      FunctionContext*, const DecimalVal&, const DecimalVal&);
  static BooleanVal Ge_DecimalVal_DecimalVal(
      FunctionContext*, const DecimalVal&, const DecimalVal&);
  static BooleanVal Gt_DecimalVal_DecimalVal(
      FunctionContext*, const DecimalVal&, const DecimalVal&);
  static BooleanVal Le_DecimalVal_DecimalVal(
      FunctionContext*, const DecimalVal&, const DecimalVal&);
  static BooleanVal Lt_DecimalVal_DecimalVal(
      FunctionContext*, const DecimalVal&, const DecimalVal&);
  static BooleanVal DistinctFrom_DecimalVal_DecimalVal(
      FunctionContext*, const DecimalVal&, const DecimalVal&);
  static BooleanVal NotDistinct_DecimalVal_DecimalVal(
      FunctionContext*, const DecimalVal&, const DecimalVal&);

  /// The rounding rule when converting decimals. These only apply going from a higher
  /// scale to a lower one.
  enum DecimalRoundOp {
    /// Additional digits are dropped.
    TRUNCATE,

    /// Returns largest value not greater than the value. (digits are dropped for
    /// positive values and rounded away from zero for negative values)
    FLOOR,

    /// Returns smallest value not smaller than the value. (rounded away from zero
    /// for positive values and extra digits dropped for negative values)
    CEIL,

    /// Rounded towards zero if the extra digits are less than .5 and away from
    /// zero otherwise.
    ROUND
  };

  /// Evaluates a round from 'val' and returns the result, using the rounding rule of
  /// 'op. Returns DecimalVal::null() on overflow.
  static DecimalVal RoundDecimal(FunctionContext* context,
      const DecimalVal& val, int val_precision, int val_scale, int output_precision,
      int output_scale, const DecimalRoundOp& op);

  /// Same as above but infers 'val_type' from the first argument type and 'output_type'
  /// from the return type according to 'context'.
  static DecimalVal RoundDecimal(
      FunctionContext* context, const DecimalVal& val, const DecimalRoundOp& op);

  /// Handles the case of rounding to a negative scale. This means rounding to a digit
  /// before the decimal point.
  /// rounding_scale is the number of digits before the decimal to round to.
  /// TODO: can this code be reorganized to combine the two version of RoundDecimal()?
  /// The implementation is similar but not quite the same.
  /// This code is, in general, harder to read because there are multiple input/output
  /// types to handle and all combinations are valid. Another option might be to use
  /// templates to generate each pair:
  ///   Decimal4Value Round(const Decimal4Value&);
  ///   Decimal8Value Round(const Decimal4Value&);
  ///   Decimal4Value Round(const Decimal8Value&);
  ///   etc.
  static DecimalVal RoundDecimalNegativeScale(FunctionContext* context,
      const DecimalVal& val, int val_precision, int val_scale, int output_precision,
      int output_scale, const DecimalRoundOp& op, int64_t rounding_scale);

 private:
  /// Converts 'val' to a DecimalVal with given precision and scale.
  static DecimalVal IntToDecimalVal(
      FunctionContext* context, int precision, int scale, int64_t val);
  static DecimalVal FloatToDecimalVal(
      FunctionContext* context, int precision, int scale, double val);

  /// Returns the value of 'val' scaled to 'output_type'.
  static DecimalVal ScaleDecimalValue(FunctionContext* context, const Decimal4Value& val,
      int val_scale, int output_precision, int output_scale);
  static DecimalVal ScaleDecimalValue(FunctionContext* context, const Decimal8Value& val,
      int val_scale, int output_precision, int output_scale);
  static DecimalVal ScaleDecimalValue(FunctionContext* context, const Decimal16Value& val,
      int val_scale, int output_precision, int output_scale);

  /// Returns the delta that needs to be added when the source decimal is rounded to
  /// target scale. Returns 0, if no rounding is necessary, or -1/1 if rounding
  /// is required.
  template <typename T>
  static T RoundDelta(const DecimalValue<T>& v, int src_scale,
      int target_scale, const DecimalRoundOp& op);

  /// Converts a decimal value (interpreted as unix time) to TimestampVal (interpreted as
  /// local time in 'local_tz' time-zone). Rounds instead of truncating if 'round' is
  /// true.
  template <typename T>
  static TimestampVal ConvertToTimestampVal(
      const T& decimal_value, int scale, bool round, const Timezone& local_tz);

  /// Converts fractional 'val' with the given 'scale' to nanoseconds. Rounds
  /// instead of truncating if 'round' is true.
  template <typename T>
  static int32_t ConvertToNanoseconds(T val, int scale, bool round);
};

}

#endif