type Item struct {
TopicId int `json:"topic_id"`
Topic *Topic `json:"topic,omitempty"`
BotId int `json:"bot_id"`
URL string `gorm:"varchar(250);unique" json:"url"`
Title string `gorm:"varchar(250)" json:"title"`
}
type Topic struct {
Title string `gorm:"varchar(250)" json:"title"`
Items []*Item `json:"items,omitempty"`
}
Here is the two models. I want to query the Topics with each have 5 latest items.
Without the limit for items, I could do this by,db.Model(&Topic{}).Preload("Items")
.
When I try to add some limit conditions to items:
db.Model(&Topic{}).Preload("Items", func(db *gorm.DB) *gorm.DB {
return db.Order("title DESC").Limit(5)
})
It will return 5 items in total, not 5 items for each topic.
Actual result:
"records": [
{
"id": 4,
"created_on": "2019-08-11T10:28:54.910022Z",
"title": "Topic 1",
},
{
"id": 5,
"created_on": "2019-08-11T10:29:26.952614Z",
"title": "Programming",
},
{
"id": 6,
"created_on": "2019-08-11T10:34:16.040229Z",
"title": "Topic 3",
"items": [
{
"id": 1,
"created_on": "2019-08-27T14:23:17.766055Z",
"topic_id": 6,
"title": "Title One",
},
......
{
"id": 5,
"created_on": "2019-08-27T14:23:17.766055Z",
"topic_id": 6,
"title": "Title five",
}
]
Expected results:
"records": [
{
"id": 4,
"created_on": "2019-08-11T10:28:54.910022Z",
"title": "Topic 1",
},
{
"id": 5,
"created_on": "2019-08-11T10:29:26.952614Z",
"title": "Programming",
"items": [
{
"id": 6,
"created_on": "2019-08-27T14:23:17.766055Z",
"topic_id": 5,
"title": "Title six",
},
......
{
"id": 10,
"created_on": "2019-08-27T14:23:17.766055Z",
"topic_id": 5,
"title": "Title ten",
}]
},
{
"id": 6,
"created_on": "2019-08-11T10:34:16.040229Z",
"title": "Topic 3",
"items": [
{
"id": 1,
"created_on": "2019-08-27T14:23:17.766055Z",
"topic_id": 6,
"title": "Title One",
},
......
{
"id": 5,
"created_on": "2019-08-27T14:23:17.766055Z",
"topic_id": 6,
"title": "Title five",
}
]
The actual sql it generated is SELECT * FROM "item" WHERE "topic_id" IN (6,4,5) DESC LIMIT 5
It's obvious not the results I want, so how should I get the expected result with gorm?