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text_inverted_index.go
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/
text_inverted_index.go
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package textinvertedindex
import (
"encoding/json"
"reflect"
"github.com/RoaringBitmap/roaring"
"github.com/rs/zerolog/log"
"github.com/segmentio/fasthash/fnv1a"
"github.com/spaghettifunk/norman/internal/storage/indexer"
"github.com/spaghettifunk/norman/pkg/containers/mapset"
)
type TextInvertedIndex[T indexer.ValidType] struct {
Metadata indexer.IndexMetadata[T] `json:"metadata"`
Index map[string]*roaring.Bitmap `json:"index"`
StopWords mapset.Set[string] `json:"-"`
}
// New creates a new Text InvertedIndex object
// English is the only language supported
func New[T indexer.ValidType](columnName string) *TextInvertedIndex[T] {
stopWords := mapset.New[string]()
for _, sw := range stopWordsEN {
stopWords.Put(sw)
}
var t T
return &TextInvertedIndex[T]{
Metadata: indexer.IndexMetadata[T]{
CastType: reflect.TypeOf(t).Kind(),
IndexType: indexer.TextInvertedIndex,
ColumnName: columnName,
},
Index: make(map[string]*roaring.Bitmap, 1_000),
StopWords: stopWords,
}
}
// AddValue adds the current value for the given id to the index
func (i *TextInvertedIndex[T]) AddValue(id string, value interface{}) bool {
// make sure we operate only with strings
document, ok := value.(string)
if !ok {
log.Error().Msg("value cannot be casted to string")
return false
}
tokens := i.analyze(document)
visited := make(map[string]bool, len(tokens))
for _, word := range tokens {
if _, ok := visited[word]; ok {
continue
}
rb, ok := i.Index[word]
if !ok {
rb = roaring.NewBitmap()
i.Index[word] = rb
}
rb.Add(fnv1a.HashString32(id))
visited[word] = true
}
return true
}
// Search queries the index for the given text.
func (i *TextInvertedIndex[T]) Search(value interface{}) []uint32 {
// make sure we operate only with strings
text, ok := value.(string)
if !ok {
log.Error().Msgf("value %x is not accepted", value)
return nil
}
var r *roaring.Bitmap
for _, token := range i.analyze(text) {
if ids, ok := i.Index[token]; ok {
if r == nil {
r = roaring.NewBitmap()
iterator := ids.Iterator()
for iterator.HasNext() {
r.Add(iterator.Next())
}
} else {
// run intersection
r = roaring.ParAnd(0, r, ids)
}
} else {
// Token doesn't exist.
return nil
}
}
return r.ToArray()
}
func (i *TextInvertedIndex[T]) GetColumnName() string {
return i.Metadata.ColumnName
}
func (i *TextInvertedIndex[T]) GetIndexType() indexer.IndexType {
return i.Metadata.IndexType
}
type TextInvertedIndexJSON[T indexer.ValidType] struct {
Metadata indexer.IndexMetadata[T] `json:"metadata"`
Indexes []TextMapIdsJSON `json:"index"`
}
type TextMapIdsJSON struct {
Key string `json:"key"`
Ids []uint32 `json:"ids"`
}
func (i *TextInvertedIndex[T]) MarshalJSON() ([]byte, error) {
textIndexes := TextInvertedIndexJSON[T]{
Metadata: i.Metadata,
}
for val, ids := range i.Index {
textIndexes.Indexes = append(textIndexes.Indexes, TextMapIdsJSON{val, ids.ToArray()})
}
return json.Marshal(textIndexes)
}
func (i *TextInvertedIndex[T]) Deserialize(data []byte) error {
textIndexes := []TextMapIdsJSON{}
if err := json.Unmarshal(data, &textIndexes); err != nil {
return err
}
for _, bi := range textIndexes {
rb := roaring.NewBitmap()
rb.AddMany(bi.Ids)
i.Index[bi.Key] = rb
}
return nil
}