README
¶
Documents
Two files are used to represent the documents in a segment. The data file contains the data for each document in the segment. The index file contains, for each document, its corresponding offset in the data file.
Data File
The data file contains the fields for each document. The documents are stored serially.
┌───────────────────────────┐
│ ┌───────────────────────┐ │
│ │ Document 1 │ │
│ ├───────────────────────┤ │
│ │ ... │ │
│ ├───────────────────────┤ │
│ │ Document n │ │
│ └───────────────────────┘ │
└───────────────────────────┘
Document
Each document is composed of an ID and its fields. The ID is a sequence of valid UTF-8 bytes and it is encoded first by encoding the length of the ID, in bytes, as a variable-sized unsigned integer and then encoding the actual bytes which comprise the ID. Following the ID are the fields. The number of fields in the document is encoded first as a variable-sized unsigned integer and then the fields themselves are encoded.
┌───────────────────────────┐
│ ┌───────────────────────┐ │
│ │ Length of ID │ │
│ │ (uvarint) │ │
│ ├───────────────────────┤ │
│ │ │ │
│ │ ID │ │
│ │ (bytes) │ │
│ │ │ │
│ ├───────────────────────┤ │
│ │ Number of Fields │ │
│ │ (uvarint) │ │
│ ├───────────────────────┤ │
│ │ │ │
│ │ Field 1 │ │
│ │ │ │
│ ├───────────────────────┤ │
│ │ │ │
│ │ ... │ │
│ │ │ │
│ ├───────────────────────┤ │
│ │ │ │
│ │ Field n │ │
│ │ │ │
│ └───────────────────────┘ │
└───────────────────────────┘
Field
Each field is composed of a name and a value. The name and value are a sequence of valid UTF-8 bytes and they are stored by encoding the length of the name (value), in bytes, as a variable-sized unsigned integer and then encoding the actual bytes which comprise the name (value). The name is encoded first and the value second.
┌───────────────────────────┐
│ ┌───────────────────────┐ │
│ │ Length of Field Name │ │
│ │ (uvarint) │ │
│ ├───────────────────────┤ │
│ │ │ │
│ │ Field Name │ │
│ │ (bytes) │ │
│ │ │ │
│ ├───────────────────────┤ │
│ │ Length of Field Value │ │
│ │ (uvarint) │ │
│ ├───────────────────────┤ │
│ │ │ │
│ │ Field Value │ │
│ │ (bytes) │ │
│ │ │ │
│ └───────────────────────┘ │
└───────────────────────────┘
Index File
The index file contains, for each postings ID in the segment, the offset of the corresponding
document in the data file. The base postings ID is stored at the start of the file as a
little-endian uint64. Following it are the actual offsets.
┌───────────────────────────┐
│ Base │
│ (uint64) │
├───────────────────────────┤
│ │
│ │
│ Offsets │
│ │
│ │
└───────────────────────────┘
Offsets
The offsets are stored serially starting from the offset for the base postings ID. Each
offset is a little-endian uint64. Since each offset is of a fixed-size we can access
the offset for a given postings ID by calculating its index relative to the start of
the offsets. An offset equal to the maximum value for a uint64 indicates that there is
no corresponding document for a given postings ID.
┌───────────────────────────┐
│ ┌───────────────────────┐ │
│ │ Offset 1 │ │
│ │ (uint64) │ │
│ ├───────────────────────┤ │
│ │ ... │ │
│ ├───────────────────────┤ │
│ │ Offset n │ │
│ │ (uint64) │ │
│ └───────────────────────┘ │
└───────────────────────────┘
Documentation
¶
Index ¶
Constants ¶
This section is empty.
Variables ¶
This section is empty.
Functions ¶
This section is empty.
Types ¶
type DataReader ¶
type DataReader struct {
// contains filtered or unexported fields
}
DataReader is a reader for the data file for documents.
func NewDataReader ¶
func NewDataReader(data []byte) *DataReader
NewDataReader returns a new DataReader.
type DataWriter ¶
type DataWriter struct {
// contains filtered or unexported fields
}
DataWriter writes the data file for documents.
func NewDataWriter ¶
func NewDataWriter(w io.Writer) *DataWriter
NewDataWriter returns a new DataWriter.
type IndexReader ¶
type IndexReader struct {
// contains filtered or unexported fields
}
IndexReader is a reader for the index file for documents.
func NewIndexReader ¶
func NewIndexReader(data []byte) (*IndexReader, error)
NewIndexReader returns a new IndexReader.
func (*IndexReader) Base ¶
func (r *IndexReader) Base() postings.ID
Base returns the base postings ID.
type IndexWriter ¶
type IndexWriter struct {
// contains filtered or unexported fields
}
IndexWriter is a writer for the index file for documents.
func NewIndexWriter ¶
func NewIndexWriter(w io.Writer) *IndexWriter
NewIndexWriter returns a new IndexWriter.
type Reader ¶ added in v0.15.14
type Reader interface {
// Len is the number of documents contained by the reader.
Len() int
// Read reads a document with the given postings ID.
Read(id postings.ID) (doc.Document, error)
// Iter returns a document iterator.
Iter() index.IDDocIterator
}
Reader is a document reader from an encoded source.
type SliceReader ¶ added in v0.5.0
type SliceReader struct {
// contains filtered or unexported fields
}
SliceReader is a docs slice reader for use with documents stored in memory.
func NewSliceReader ¶ added in v0.5.0
func NewSliceReader(docs []doc.Document) *SliceReader
NewSliceReader returns a new docs slice reader.
func (*SliceReader) Doc ¶ added in v0.15.0
Doc implements DocRetriever and reads the document with postings ID.
func (*SliceReader) Iter ¶ added in v0.15.14
func (r *SliceReader) Iter() index.IDDocIterator
Iter returns a docs iterator.
func (*SliceReader) Len ¶ added in v0.5.0
func (r *SliceReader) Len() int
Len returns the number of documents in the slice reader.
Source Files