github.com/m3db/m3@v1.5.0/src/query/functions/linear/round.go (about)

     1  // Copyright (c) 2018 Uber Technologies, Inc.
     2  //
     3  // Permission is hereby granted, free of charge, to any person obtaining a copy
     4  // of this software and associated documentation files (the "Software"), to deal
     5  // in the Software without restriction, including without limitation the rights
     6  // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
     7  // copies of the Software, and to permit persons to whom the Software is
     8  // furnished to do so, subject to the following conditions:
     9  //
    10  // The above copyright notice and this permission notice shall be included in
    11  // all copies or substantial portions of the Software.
    12  //
    13  // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
    14  // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
    15  // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
    16  // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
    17  // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
    18  // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
    19  // THE SOFTWARE.
    20  
    21  package linear
    22  
    23  import (
    24  	"fmt"
    25  	"math"
    26  
    27  	"github.com/m3db/m3/src/query/block"
    28  	"github.com/m3db/m3/src/query/functions/lazy"
    29  	"github.com/m3db/m3/src/query/parser"
    30  )
    31  
    32  // RoundType rounds each datapoint in the series.
    33  // Ties are resolved by rounding up. The optional to_nearest argument allows
    34  // specifying the nearest multiple to which the timeseries values should be
    35  // rounded (default=1). This variable may be a fraction.
    36  // Special cases are: round(_, 0) = NaN
    37  const RoundType = "round"
    38  
    39  type roundOp struct {
    40  	toNearest float64
    41  }
    42  
    43  func parseArgs(args []interface{}) (float64, error) {
    44  	// NB: if no args passed; this should use default value of `1`.
    45  	if len(args) == 0 {
    46  		return 1, nil
    47  	}
    48  
    49  	if len(args) > 1 {
    50  		return 0, fmt.Errorf("invalid number of args for round: %d", len(args))
    51  	}
    52  
    53  	// Attempt to parse a single arg.
    54  	if nearest, ok := args[0].(float64); ok {
    55  		return nearest, nil
    56  	}
    57  
    58  	return 0, fmt.Errorf("unable to cast to to_nearest argument: %v", args[0])
    59  }
    60  
    61  func roundFn(roundTo float64) block.ValueTransform {
    62  	if roundTo == 0 {
    63  		return func(float64) float64 { return math.NaN() }
    64  	}
    65  
    66  	roundToInverse := 1.0 / roundTo
    67  	return func(v float64) float64 {
    68  		return math.Floor(v*roundToInverse+0.5) / roundToInverse
    69  	}
    70  }
    71  
    72  // NewRoundOp creates a new round op based on the type and arguments.
    73  func NewRoundOp(args []interface{}) (parser.Params, error) {
    74  	toNearest, err := parseArgs(args)
    75  	if err != nil {
    76  		return nil, err
    77  	}
    78  
    79  	lazyOpts := block.NewLazyOptions().SetValueTransform(roundFn(toNearest))
    80  	return lazy.NewLazyOp(RoundType, lazyOpts)
    81  }