It's possible to shorten table relation aliases?

[un-versed]

Hi @vmihailenco! It's possible to shorten table relation aliases?

I'm facing an issue similar to #524.

I have this example code (I've changed the table and struct names, because I can't share the project data):

type TheNameOfStructInPrivCodebase struct {
	bun.BaseModel          `bun:"table:the_name_of_table_in_the_database,alias:osih"`
	ID                     int64     `json:"id" bun:"id,pk,autoincrement"`
	TheNameOfSecondTableID int64     `json:"the_name_of_second_table_id"`
	CreatedAt              time.Time `json:"created_at" bun:",nullzero,notnull,default:current_timestamp"`
	UpdatedAt              time.Time `json:"updated_at" bun:",nullzero,notnull,default:current_timestamp"`
	// Relationships
	TheNameOfSecondStruct *TheNameOfSecondStruct `json:"the_name_of_second_table" bun:"rel:belongs-to,join:the_name_of_second_table_id=id"`
}

type TheNameOfSecondStruct struct {
	bun.BaseModel         `bun:"table:the_name_of_second_table,alias:osi"`
	ID                    int64     `json:"id" bun:"id,pk,autoincrement"`
	TheNameOfThirdTableID int64     `json:"the_name_of_third_table_id"`
	CreatedAt             time.Time `json:"created_at" bun:",nullzero,notnull,default:current_timestamp"`
	UpdatedAt             time.Time `json:"updated_at" bun:",nullzero,notnull,default:current_timestamp"`
	// Relationships
	TheNameOfThirdStruct *TheNameOfThirdStruct `json:"the_name_of_third_table" bun:"rel:belongs-to,join:the_name_of_third_table_id=id"`
}

type TheNameOfThirdStruct struct {
	bun.BaseModel       `bun:"table:the_name_of_third_table,alias:oi"`
	ID                  int64     `json:"id" bun:"id,pk,autoincrement"`
	ThisInformationUUID string    `json:"this_information_uuid"`
	CreatedAt           time.Time `json:"created_at" bun:",nullzero,notnull,default:current_timestamp"`
	UpdatedAt           time.Time `json:"updated_at" bun:",nullzero,notnull,default:current_timestamp"`
}

func GetData(id int64) (*TheNameOfStructInPrivCodebase, error) {
	db := db.Conn()
	db.AddQueryHook(bundebug.NewQueryHook())

	m := new(TheNameOfStructInPrivCodebase)
	err := db.NewSelect().
		Model(m).
		Relation("TheNameOfSecondStruct").
		Relation("TheNameOfSecondStruct.TheNameOfThirdStruct").
		Where("osih.id = ?", id).
		Scan(context.TODO())

	return m, err
}

Calling GetData returns this error:
sql: Scan error on column index 14, name \"the_name_of_second_table__the_name_of_third_table__this_informa\": bun: TheNameOfThirdStruct does not have column \"this_informa\""

After some research, I found about NAMEDATALEN-1 in PostgreSQL. Which is (in short) a constant to limit the names of tables and columns in the database, with a value of 63 bytes.

In my case, bun is generating an alias with 72 bytes:
the_name_of_second_table__the_name_of_third_table__this_information_uuid

Then, by default, PostgreSQL slices the alias generating a different one: the_name_of_second_table__the_name_of_third_table__this_informa
(the string is missing the last characters: ...tion_uuid)

The problem is: bun uses this alias notation to Scan the rows into structs:
table_name__other_table_name__column_to_scan

After the slice, bun is searching for a field called this_informa to scan, but this field doesn't exists. The right one is this_information_uuid.

There's a way to shorten the alias generated by bun?

P.S.: I've tried using the bun:"alias:table_alias" struct tag, but it didn't work for my case.

Additional info:

I found this old issue in sequelize repo, sequelize/sequelize#2084

I think i'ts the same issue... But in sequelize, they created a way to "minify" the ORM aliases.

sequelize/sequelize#11095

[un-versed]

I found a way to do this:

type TheNameOfStructInPrivCodebase struct {
	bun.BaseModel          `bun:"table:the_name_of_table_in_the_database,alias:osih"`
	ID                     int64     `json:"id" bun:"id,pk,autoincrement"`
	TheNameOfSecondTableID int64     `json:"the_name_of_second_table_id"`
	CreatedAt              time.Time `json:"created_at" bun:",nullzero,notnull,default:current_timestamp"`
	UpdatedAt              time.Time `json:"updated_at" bun:",nullzero,notnull,default:current_timestamp"`
	// Relationships
	TheNameOfSecondStruct *TheNameOfSecondStruct `json:"the_name_of_second_table" bun:"osi,rel:belongs-to,join:the_name_of_second_table_id=id"`
}

type TheNameOfSecondStruct struct {
	bun.BaseModel         `bun:"table:the_name_of_second_table,alias:osi"`
	ID                    int64     `json:"id" bun:"id,pk,autoincrement"`
	TheNameOfThirdTableID int64     `json:"the_name_of_third_table_id"`
	CreatedAt             time.Time `json:"created_at" bun:",nullzero,notnull,default:current_timestamp"`
	UpdatedAt             time.Time `json:"updated_at" bun:",nullzero,notnull,default:current_timestamp"`
	// Relationships
	TheNameOfThirdStruct *TheNameOfThirdStruct `json:"the_name_of_third_table" bun:"oi,rel:belongs-to,join:the_name_of_third_table_id=id"`
}

type TheNameOfThirdStruct struct {
	bun.BaseModel       `bun:"table:the_name_of_third_table,alias:oi"`
	ID                  int64     `json:"id" bun:"id,pk,autoincrement"`
	ThisInformationUUID string    `json:"this_information_uuid"`
	CreatedAt           time.Time `json:"created_at" bun:",nullzero,notnull,default:current_timestamp"`
	UpdatedAt           time.Time `json:"updated_at" bun:",nullzero,notnull,default:current_timestamp"`
}

func GetData(id int64) (*TheNameOfStructInPrivCodebase, error) {
	db := db.Conn()
	db.AddQueryHook(bundebug.NewQueryHook())

	m := new(TheNameOfStructInPrivCodebase)
	err := db.NewSelect().
		Model(m).
		Relation("TheNameOfSecondStruct").
		Relation("TheNameOfSecondStruct.TheNameOfThirdStruct").
		Where("osih.id = ?", id).
		Scan(context.TODO())

	return m, err
}

Notice that in TheNameOfStructInPrivCodebase', I added bun:"osi,[...] tag, inside of TheNameOfSecondStruct relationship reference... This tag "Override default column name." (as described in the docs).

I don't know if it was a misunderstanding, but it wasn't clear to me that I should use a tag that changes a column name as an alias in a table relationship...

It would be nice if bun used the alias already defined in the child structure (bun:"table:the_name_of_third_table,alias:oi"). (It should be an improvement? Or a bug? @vmihailenco)

Anyway, I'm going to mark this as solved, but I think it's a good discussion for an improvement.

Wrapping up: if you want to use custom alias names in bun relationship queries, just set the column_name tag as the name you want.