gorm Count() erases SELECTs for Joins() statement if executed before a Find()

Count() erases SELECTs for Joins() statement if executed before a Find()

Open dschreij opened this issue 1 year ago • 2 comments

GORM Playground Link

https://github.com/go-gorm/playground/pull/681

Description

If you add a Joins() preload statement to a *gorm.DB transaction instance, the select statements to loads field from the relationship seems to be nullified if you first call tx.Count() and then afterwards with the same tx also call tx.Find(). The tx.Find() no longer selects the fields from the joined tables, e.g.

var res []MyModel
tx := db.Model(&MyModel)
tx.Joins("OtherModel")
var cnt *int64
tx.Count(&cnt)
tx.Find(&res)
// res.OtherModel.<somefield> is empty as SELECT for OtherModels have disappeared from the query

A use case for this scenario is if you are paginating: You first want to get the total records in the DB to show in the UI (or calculate the amount of pages) and after doing so, you apply a limit and offset to the tx to obtain a subset of the results.

If you call the join statements again, this results in an error:

var res []MyModel
tx := db.Model(&MyModel)
tx.Joins("OtherModel")
var cnt *int64
tx.Count(&cnt)
tx.Joins("OtherModel")
tx.Find(&res)

pq: table name \"OtherModel\" specified more than once

Jan 10 '24 15:01 dschreij

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