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limitations.md

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Limitations

The following limitations are currently known:

Limitation Workaround
OnConflict OnConflict clauses are not supported
Nested transactions Nested transactions and savepoints are not supported. It is therefore recommended to set the configuration option DisableNestedTransaction: true,
Locking Lock clauses (e.g. clause.Locking{Strength: "UPDATE"}) are not supported. These are generally speaking also not required, as the default isolation level that is used by Cloud Spanner is serializable.
Auto-save associations Auto saved associations are not supported, as these will automatically use an OnConflict clause
Session Labelling Session labelling is not supported.
Request Priority Request priority is not supported.
Request Tag Request tag is not supported.
Request Options Request options are not supported.
Partitioned queries Partitioned queries are not supported.
Backups Backups are not supported by this driver. Use the Cloud Spanner Go client library <https://github.com/googleapis/google-cloud-go/tree/main/spanner>_ to manage backups programmatically.

OnConflict Clauses

OnConflict clauses are not supported by Cloud Spanner and should not be used. The following will therefore not work.

user := User{
    ID:   1,
    Name: "User Name",
}
// OnConflict is not supported and this will return an error.
db.Clauses(clause.OnConflict{DoNothing: true}).Create(&user)

Auto-save Associations

Auto-saving associations will automatically use an OnConflict clause in gorm. These are not supported. Instead, the parent entity of the association must be created before the child entity is created.

blog := Blog{
    ID:     1,
    Name:   "",
    UserID: 1,
    User: User{
        ID:   1,
        Name: "User Name",
    },
}
// This will fail, as the insert statement for User will use an OnConflict clause.
db.Create(&blog).Error

Instead, do the following:

user := User{
    ID:   1,
    Name: "User Name",
    Age:  20,
}
blog := Blog{
    ID:     1,
    Name:   "",
    UserID: 1,
}
db.Create(&user)
db.Create(&blog)

Nested Transactions

gorm uses savepoints for nested transactions. Savepoints are currently not supported by Cloud Spanner. Nested transactions can therefore not be used with GORM.

Locking

Locking clauses, like clause.Locking{Strength: "UPDATE"}, are not supported. These are generally speaking also not required, as Cloud Spanner uses isolation level serializable for read/write transactions.