github.com/m3db/m3@v1.5.0/src/m3ninx/index/segment/fst/encoding/docs/slice.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 Softwarw.
    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 docs
    22  
    23  import (
    24  	"errors"
    25  
    26  	"github.com/m3db/m3/src/m3ninx/doc"
    27  	"github.com/m3db/m3/src/m3ninx/index"
    28  	"github.com/m3db/m3/src/m3ninx/postings"
    29  )
    30  
    31  var (
    32  	errDocNotFound = errors.New("doc not found")
    33  )
    34  
    35  var _ Reader = (*SliceReader)(nil)
    36  var _ index.MetadataRetriever = (*SliceReader)(nil)
    37  
    38  // SliceReader is a docs slice reader for use with documents
    39  // stored in memory.
    40  type SliceReader struct {
    41  	docs []doc.Metadata
    42  }
    43  
    44  // NewSliceReader returns a new docs slice reader.
    45  func NewSliceReader(docs []doc.Metadata) *SliceReader {
    46  	return &SliceReader{docs: docs}
    47  }
    48  
    49  // Len returns the number of documents in the slice reader.
    50  func (r *SliceReader) Len() int {
    51  	return len(r.docs)
    52  }
    53  
    54  // Read returns a document from the docs slice reader.
    55  func (r *SliceReader) Read(id postings.ID) (doc.Metadata, error) {
    56  	idx := int(id)
    57  	if idx < 0 || idx >= len(r.docs) {
    58  		return doc.Metadata{}, errDocNotFound
    59  	}
    60  
    61  	return r.docs[idx], nil
    62  }
    63  
    64  // Metadata implements MetadataRetriever and reads the document with postings ID.
    65  func (r *SliceReader) Metadata(id postings.ID) (doc.Metadata, error) {
    66  	return r.Read(id)
    67  }
    68  
    69  // Iter returns a docs iterator.
    70  func (r *SliceReader) Iter() index.IDDocIterator {
    71  	postingsIter := postings.NewRangeIterator(0, postings.ID(r.Len()))
    72  	return index.NewIDDocIterator(r, postingsIter)
    73  }