Gorm Gorm Automigrate with MSSQL fails if migration run for nTime (not first time)

Your Question

I have a model

type Numbering struct {
gorm.Model
Year int `gorm:"check:year>0;" json:"year"`
... other fieds
}

func Migrate (tx * gorm.DB) error {
if err := tx.AutoMigrate(&Numbering{}); err != nil {return err }
return nil 

if is the first time migration then migration goes well, but if you modify structs and want to run migration again , instead of altering model and drop existing constraint/index if existing and create a new one, it modify database table by adding new constraint/index with same name. As the result I got db error

go:64 mssql: Could not create constraint or index. See previous errors.
[191.354ms] [rows:0] ALTER TABLE "Numbering" ADD CONSTRAINT "chk_Numbering_Period" CHECK (period>0)
mssql: Could not create constraint or index. See previous errors.

gorm AuotMigrate per each model to drop existing constraints and create a new constraints but it adding as if it does not exists

The document you expected this should be explained

Expected answer

There is a possibility to alter AutoMigrate to check for constraint/index before re-creating them

Comment From: rngallen

After following I have discovered the query used to check constraint by gorm

SELECT count(*) FROM sys.foreign_keys as F inner join sys.tables as T on F.parent_object_id=T.object_id inner join INFORMATION_SCHEMA.TABLES as I on I.TABLE_NAME = T.name WHERE F.name = 'chk_numbering_year' AND I.TABLE_NAME = 'numberings' AND I.TABLE_SCHEMA like '%' AND I.TABLE_CATALOG = 'EVOERMS';

returns null as sys.foregin_keys as no value as it was supposed to be

SELECT count(*) FROM sys.check_constraints as F inner join sys.tables as T 
on F.parent_object_id=T.object_id inner 
join INFORMATION_SCHEMA.TABLES as I on I.TABLE_NAME = T.name WHERE F.name = 'chk_numbering_year' 
AND I.TABLE_NAME = 'numberings' AND I.TABLE_SCHEMA like '%' AND I.TABLE_CATALOG = 'EVOERMS';