如何在 Sequelize ORM 中限制连接行(多对多关联)? [英] How to limit joined rows (many-to-many association) in Sequelize ORM?

问题描述

Sequelize 定义了两种模型:多对多关联的 Post 和 Tag.

There are two models defined by Sequelize: Post and Tag with many-to-many association.

Post.belongsToMany(db.Tag, {through: 'post_tag', foreignKey: 'post_id', timestamps: false});
Tag.belongsToMany(db.Post, {through: 'post_tag', foreignKey: 'tag_id',timestamps: false});

在标签"页面上，我想获取标签数据、相关帖子并用分页显示它们.所以我应该限制帖子.但是如果我尝试将它们限制在包含"中

On a "tag" page I want to get tag data, associated posts and show them with pagination. So I should limit posts. But If I try limit them inside "include"

Tag.findOne({
    where: {url: req.params.url},
    include: [{
        model : Post,
        limit: 10
    }]
}).then(function(tag) {
    //handling results
});

我收到以下错误:

Unhandled rejection Error: Only HasMany associations support include.separate

如果我尝试切换到HasMany"关联，则会出现以下错误

If I try to switch to "HasMany" associations I get following error

Error: N:M associations are not supported with hasMany. Use belongsToMany instead

并且从其他方面的文档中可以看出该限制选项仅支持 include.separate=true".如何解决这个问题?

And from other side documentation says that limit option "only supported with include.separate=true". How to solve this problem?

推荐答案

我知道这个问题很老了，但对于那些仍然遇到这个问题的人来说，有一个简单的解决方法.

I know this question is old but for those of you still experiencing this issue, there's a simple workaround.

由于 Sequelize 向实例添加了自定义方法在关联模型中，您可以将代码重构为如下所示:

Since Sequelize adds custom methods to instances of associated models, you could restructure your code to something like this:

const tag = await Tag.findOne({ where: { url: req.params.url } });
const tagPosts = await tag.getPosts({ limit: 10 });

这与您的代码的工作方式完全相同，但可以进行限制和抵消.

This would work the exact same way as your code but with limiting and offsetting possible.

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