mgo不保证不同的指标

Question

I am using following go file as layer between my http API and mgo:

package store

import (
    "reflect"
    "strings"

    "labix.org/v2/mgo"
    "labix.org/v2/mgo/bson"
)

type Manager struct {
    collection *mgo.Collection
}

type Model interface {
    Id() bson.ObjectId
}

func (m *Manager) index(model Model) {
    v := reflect.ValueOf(model).Elem()

    var index, unique []string

    for i := 0; i < v.NumField(); i++ {
        t := v.Type().Field(i)

        if s := t.Tag.Get("store"); len(s) != 0 {
            if strings.Contains(s, "index") {
                index = append(index, t.Name)
            }
            if strings.Contains(s, "unique") {
                unique = append(unique, t.Name)
            }
        }
    }

    m.collection.EnsureIndex(mgo.Index{Key: index})
    m.collection.EnsureIndex(mgo.Index{Key: unique, Unique: true})
}

func (m *Manager) Create(model Model) error {
    m.index(model)

    return m.collection.Insert(model)
}

func (m *Manager) Update(model Model) error {
    m.index(model)

    return m.collection.UpdateId(model.Id(), model)
}

func (m *Manager) Destroy(model Model) error {
    m.index(model)

    return m.collection.RemoveId(model.Id())
}

func (m *Manager) Find(query Query, models interface{}) error {
    return m.collection.Find(query).All(models)
}

func (m *Manager) FindOne(query Query, model Model) error {
    m.index(model)

    return m.collection.Find(query).One(model)
}

As you see I am ensuring indices on each operation by calling m.index(model). The model type has tags of form store:"index" or store:"unique".

As setting a general index is different from setting a unique index I collect them separately and then call m.collection.EnsureIndex on the resolved keys.

However the second call to m.collection.EnsureIndex does never reach the server only the normal indices were sent.

A look into the godocs shows that ensure Index caches its calls so I think I should combine them in one call.

So how do I combine different index settings in one call to EnsureIndex?

Solution: You need to lower case field names from reflect to use them with mgo...

Answer 1

The problem description seems to imply you have unique and non-unique index on the same set of fields. That's an additional unnecessary overhead.. just create one unique index in those cases.