decimal-operators.h

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// Copyright 2014 Cloudera Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.


#ifndef IMPALA_EXPRS_DECIMAL_OPERATORS_H
#define IMPALA_EXPRS_DECIMAL_OPERATORS_H

#include <stdint.h>
#include "runtime/decimal-value.h"
#include "udf/udf.h"

using namespace impala_udf;

namespace impala {

class Expr;
struct ExprValue;
class TupleRow;

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&);

  enum DecimalRoundOp {
    TRUNCATE,

    FLOOR,

    CEIL,

    ROUND
  };

  static DecimalVal RoundDecimal(
      FunctionContext* context, const DecimalVal& val, const ColumnType& val_type,
      const ColumnType& output_type, const DecimalRoundOp& op);

  static DecimalVal RoundDecimal(
      FunctionContext* context, const DecimalVal& val, const DecimalRoundOp& op);

  static DecimalVal RoundDecimalNegativeScale(
      FunctionContext* context, const DecimalVal& val, const ColumnType& val_type,
      const ColumnType& output_type, const DecimalRoundOp& op, int64_t rounding_scale);

 private:
  static DecimalVal IntToDecimalVal(
      FunctionContext* context, const ColumnType& type, int64_t val);
  static DecimalVal FloatToDecimalVal(
      FunctionContext* context, const ColumnType& type, double val);

  static DecimalVal ScaleDecimalValue(
      FunctionContext* context, const Decimal4Value& val, const ColumnType& val_type,
      const ColumnType& output_type);
  static DecimalVal ScaleDecimalValue(
      FunctionContext* context, const Decimal8Value& val, const ColumnType& val_type,
      const ColumnType& output_type);
  static DecimalVal ScaleDecimalValue(
      FunctionContext* context, const Decimal16Value& val, const ColumnType& val_type,
      const ColumnType& output_type);

  template <typename T>
  static T RoundDelta(const DecimalValue<T>& v, int src_scale, int target_scale,
      const DecimalRoundOp& op) {
    if (op == TRUNCATE) return 0;

    // Adding more digits, rounding does not apply. New digits are just 0.
    if (src_scale <= target_scale) return 0;

    // No need to round for floor() and the value is positive or ceil() and the value
    // is negative.
    if (v.value() > 0 && op == FLOOR) return 0;
    if (v.value() < 0 && op == CEIL) return 0;

    // We are removing the decimal places. Extract the value of the digits we are
    // dropping. For example, going from scale 5->2, means we want the last 3 digits.
    int delta_scale = src_scale - target_scale;
    DCHECK_GT(delta_scale, 0);

    // 10^delta_scale
    T trailing_base = DecimalUtil::GetScaleMultiplier<T>(delta_scale);
    T trailing_digits = v.value() % trailing_base;

    // If the trailing digits are zero, never round.
    if (trailing_digits == 0) return 0;

    // Trailing digits are non-zero.
    if (op == CEIL) return 1;
    if (op == FLOOR) return -1;

    DCHECK_EQ(op, ROUND);
    // TODO: > or greater than or equal. i.e. should .500 round up?
    if (abs(trailing_digits) < trailing_base / 2) return 0;
    return v.value() < 0 ? -1 : 1;
  }
};

}

#endif