mongoDB/mongoose:如果不为null，则为唯一 [英] mongoDB/mongoose: unique if not null

问题描述

我想知道是否有办法强制唯一集合条目，但仅当条目不为空时. Ë 示例架构:

I was wondering if there is way to force a unique collection entry but only if entry is not null. e Sample schema:

var UsersSchema = new Schema({
    name  : {type: String, trim: true, index: true, required: true},
    email : {type: String, trim: true, index: true, unique: true}
});

在这种情况下不需要'email'，但是如果保存了'email'，我想确保该条目是唯一的(在数据库级别).

'email' in this case is not required but if 'email' is saved I want to make sure that this entry is unique (on a database level).

空条目的值似乎为'null'，因此每个邮件都不会通过'unique'选项崩溃(如果有其他用户没有电子邮件).

Empty entries seem to get the value 'null' so every entry wih no email crashes with the 'unique' option (if there is a different user with no email).

现在我正在应用程序级别上解决它，但是很想保存该数据库查询.

Right now I'm solving it on an application level, but would love to save that db query.

thx

推荐答案

从MongoDB v1.8 +开始，您可以通过将sparse选项设置为true来获得确保唯一值但允许多个文档不包含字段的期望行为.在定义索引时.如:

As of MongoDB v1.8+ you can get the desired behavior of ensuring unique values but allowing multiple docs without the field by setting the sparse option to true when defining the index. As in:

email : {type: String, trim: true, index: true, unique: true, sparse: true}

或在外壳中:

db.users.ensureIndex({email: 1}, {unique: true, sparse: true});

请注意，唯一的稀疏索引仍然不允许具有email字段且 value 为null的多个文档，只有多个文档没有和email字段.

Note that a unique, sparse index still does not allow multiple docs with an email field with a value of null, only multiple docs without an email field.

请参见 http://docs.mongodb.org/manual/core/index-sparse/

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