github.com/m3db/m3@v1.5.0/src/m3ninx/index/segment/mem/unique_fields_iterator.go (about)

     1  // Copyright (c) 2020 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 mem
    22  
    23  import (
    24  	"bytes"
    25  	"sort"
    26  
    27  	sgmt "github.com/m3db/m3/src/m3ninx/index/segment"
    28  	"github.com/m3db/m3/src/m3ninx/postings"
    29  )
    30  
    31  type uniqueField struct {
    32  	field        []byte
    33  	postingsList postings.List
    34  }
    35  
    36  type uniqueFieldsIter struct {
    37  	err  error
    38  	done bool
    39  
    40  	currentIdx   int
    41  	current      uniqueField
    42  	backingSlice []uniqueField
    43  	opts         Options
    44  }
    45  
    46  var _ sgmt.FieldsPostingsListIterator = &uniqueFieldsIter{}
    47  
    48  func newUniqueFieldsIter(slice []uniqueField, opts Options) *uniqueFieldsIter {
    49  	sortSliceOfUniqueFields(slice)
    50  	return &uniqueFieldsIter{
    51  		currentIdx:   -1,
    52  		backingSlice: slice,
    53  		opts:         opts,
    54  	}
    55  }
    56  
    57  func (b *uniqueFieldsIter) Next() bool {
    58  	if b.done || b.err != nil {
    59  		return false
    60  	}
    61  	b.currentIdx++
    62  	if b.currentIdx >= len(b.backingSlice) {
    63  		b.done = true
    64  		return false
    65  	}
    66  	b.current = b.backingSlice[b.currentIdx]
    67  	return true
    68  }
    69  
    70  func (b *uniqueFieldsIter) Current() ([]byte, postings.List) {
    71  	return b.current.field, b.current.postingsList
    72  }
    73  
    74  func (b *uniqueFieldsIter) Err() error {
    75  	return nil
    76  }
    77  
    78  func (b *uniqueFieldsIter) Len() int {
    79  	return len(b.backingSlice)
    80  }
    81  
    82  func (b *uniqueFieldsIter) Close() error {
    83  	b.current = uniqueField{}
    84  	return nil
    85  }
    86  
    87  func sortSliceOfUniqueFields(b []uniqueField) {
    88  	sort.Slice(b, func(i, j int) bool {
    89  		return bytes.Compare(b[i].field, b[j].field) < 0
    90  	})
    91  }