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Use aggregations to calculate tags

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This commit is contained in:
Las Zenow 2014-02-18 21:35:26 +01:00
parent b3fd8aabe2
commit 706fc88a61
1 changed files with 25 additions and 13 deletions
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38
mapreduce.go
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@ -10,7 +10,7 @@ func GetTags(numTags int, tagsColl *mgo.Collection) ([]string, error) {
var result []struct { var result []struct {
Tag string "_id" Tag string "_id"
} }
err := tagsColl.Find(nil).Sort("-value").Limit(numTags).All(&result) err := tagsColl.Find(nil).Sort("-count").Limit(numTags).All(&result)
if err != nil { if err != nil {
return nil, err return nil, err
} }
@ -55,18 +55,30 @@ func NewMR(database *mgo.Database) *MR {
} }
func (m *MR) UpdateTags(booksColl *mgo.Collection) error { func (m *MR) UpdateTags(booksColl *mgo.Collection) error {
var mr mgo.MapReduce var tags []struct {
mr.Map = `function() { Tag string "_id"
if (this.subject) { Count int "count"
this.subject.forEach(function(s) { emit(s, 1); }); }
} err := booksColl.Pipe([]bson.M{
}` {"$project": bson.M{"subject": 1}},
mr.Reduce = `function(tag, vals) { {"$unwind": "$subject"},
var count = 0; {"$group": bson.M{"_id": "$subject", "count": bson.M{"$sum": 1}}},
vals.forEach(function() { count += 1; }); {"$sort": bson.M{"count": -1}},
return count; {"$limit": TAGS_DISPLAY},
}` }).All(&tags)
return m.update(&mr, bson.M{"active": true}, booksColl, TAGS_COLL) if err != nil {
return err
}
tagsColl := m.database.C(TAGS_COLL)
tagsColl.DropCollection()
for _, tag := range tags {
err = tagsColl.Insert(tag)
if err != nil {
return err
}
}
return nil
} }
func (m *MR) UpdateMostVisited(statsColl *mgo.Collection) error { func (m *MR) UpdateMostVisited(statsColl *mgo.Collection) error {