github.com/m3db/m3@v1.5.0/src/m3ninx/search/searcher/conjunction.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 searcher
    22  
    23  import (
    24  	"sort"
    25  
    26  	"github.com/m3db/m3/src/m3ninx/index"
    27  	"github.com/m3db/m3/src/m3ninx/postings"
    28  	"github.com/m3db/m3/src/m3ninx/search"
    29  )
    30  
    31  type conjunctionSearcher struct {
    32  	searchers search.Searchers
    33  	negations search.Searchers
    34  }
    35  
    36  // NewConjunctionSearcher returns a new Searcher which matches documents which match each
    37  // of the given searchers and none of the negations.
    38  func NewConjunctionSearcher(searchers, negations search.Searchers) (search.Searcher, error) {
    39  	if len(searchers) == 0 {
    40  		return nil, errEmptySearchers
    41  	}
    42  
    43  	return &conjunctionSearcher{
    44  		searchers: searchers,
    45  		negations: negations,
    46  	}, nil
    47  }
    48  
    49  func (s *conjunctionSearcher) Search(r index.Reader) (postings.List, error) {
    50  	var (
    51  		pl           postings.List
    52  		plNeedsClone = true
    53  	)
    54  
    55  	listCount := len(s.searchers)
    56  	if listCount < len(s.negations) {
    57  		listCount = len(s.negations)
    58  	}
    59  	lists := make([]postingsListWithLength, 0, listCount)
    60  
    61  	for _, sr := range s.searchers {
    62  		curr, err := sr.Search(r)
    63  		if err != nil {
    64  			return nil, err
    65  		}
    66  		lists = append(lists, postingsListWithLength{
    67  			list:   curr,
    68  			length: curr.Len(),
    69  		})
    70  	}
    71  
    72  	sort.Sort(byLengthAscending(lists))
    73  	for _, curr := range lists {
    74  		if pl == nil {
    75  			pl = curr.list
    76  		} else {
    77  			var err error
    78  			pl, err = pl.Intersect(curr.list)
    79  			if err != nil {
    80  				return nil, err
    81  			}
    82  			plNeedsClone = false
    83  		}
    84  
    85  		// We can break early if the intersected postings list is ever empty.
    86  		if pl.IsEmpty() {
    87  			break
    88  		}
    89  	}
    90  
    91  	lists = lists[:0]
    92  	for _, sr := range s.negations {
    93  		curr, err := sr.Search(r)
    94  		if err != nil {
    95  			return nil, err
    96  		}
    97  		lists = append(lists, postingsListWithLength{
    98  			list:   curr,
    99  			length: curr.Len(),
   100  		})
   101  	}
   102  
   103  	sort.Sort(byLengthDescending(lists))
   104  	for _, curr := range lists {
   105  		// We can break early if the resulting postings list is ever empty.
   106  		if pl.IsEmpty() {
   107  			break
   108  		}
   109  
   110  		var err error
   111  		pl, err = pl.Difference(curr.list)
   112  		if err != nil {
   113  			return nil, err
   114  		}
   115  		plNeedsClone = false
   116  	}
   117  
   118  	if pl != nil && plNeedsClone {
   119  		// There was no new instance created indirectly (by Intersect/Difference), so need to clone.
   120  		pl = pl.CloneAsMutable()
   121  	}
   122  
   123  	return pl, nil
   124  }
   125  
   126  type postingsListWithLength struct {
   127  	list   postings.List
   128  	length int
   129  }
   130  
   131  type byLengthAscending []postingsListWithLength
   132  
   133  func (l byLengthAscending) Len() int {
   134  	return len(l)
   135  }
   136  
   137  func (l byLengthAscending) Less(i, j int) bool {
   138  	return l[i].length < l[j].length
   139  }
   140  
   141  func (l byLengthAscending) Swap(i, j int) {
   142  	l[i], l[j] = l[j], l[i]
   143  }
   144  
   145  type byLengthDescending []postingsListWithLength
   146  
   147  func (l byLengthDescending) Len() int {
   148  	return len(l)
   149  }
   150  
   151  func (l byLengthDescending) Less(i, j int) bool {
   152  	return l[i].length > l[j].length
   153  }
   154  
   155  func (l byLengthDescending) Swap(i, j int) {
   156  	l[i], l[j] = l[j], l[i]
   157  }