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/
extractor.go
97 lines (75 loc) · 1.91 KB
/
extractor.go
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package main
import (
"database/sql"
"encoding/json"
"github.com/cloudflare/ahocorasick"
_ "github.com/lib/pq"
)
// An entity (which has an ID and several representative strings)
type Entity struct {
id string
}
type Entities struct {
terms []string
termOffsetToEntity []*Entity
}
type Extractor struct {
cfg *Config
entities Entities
matcher *ahocorasick.Matcher
}
func NewExtractor(cfg *Config) *Extractor {
return &Extractor{cfg: cfg}
}
func (self *Entities) addEntity(id string, termsJson string) error {
entity := Entity{id}
var terms []string
err := json.Unmarshal([]byte(termsJson), &terms)
if err != nil {
return err
}
for _, term := range terms {
self.terms = append(self.terms, term)
self.termOffsetToEntity = append(self.termOffsetToEntity, &entity)
}
return nil
}
func (extr *Extractor) LoadEntities() error {
return extr.loadEntitiesFromDatabase(extr.cfg.dbConnectionString)
}
func (extr *Extractor) loadEntitiesFromDatabase(dbConnectionString string) error {
db, err := sql.Open("postgres", dbConnectionString)
if err != nil {
return err
}
rows, err := db.Query("SELECT id, terms FROM entities")
if err != nil {
return err
}
defer rows.Close()
var entities Entities
for rows.Next() {
var id, terms string
if err := rows.Scan(&id, &terms); err != nil {
return err
}
if err := entities.addEntity(id, terms); err != nil {
return err
}
}
if err := rows.Err(); err != nil {
return err
}
extr.matcher = ahocorasick.NewStringMatcher(entities.terms)
logInfo("Loaded", len(entities.terms), "terms")
extr.entities = entities
return nil
}
func (extr *Extractor) Extract(text string) []string {
matchIndexes := extr.matcher.Match([]byte(text))
matchingTermIds := make([]string, 0, 1000)
for _, termIndex := range matchIndexes {
matchingTermIds = append(matchingTermIds, extr.entities.termOffsetToEntity[termIndex].id)
}
return matchingTermIds
}