Question: Is the DEFAULT value the final determination of whether to alter a Column correct?

[keif888]

Your Question

Why does the default value on a column being the same between the database and the struct prevent an alter being generated for a column? (For SQLite it's a drop/recreate that should be done)

For example a struct with:
TextColumn string `gorm:"type:bytes;size:255;index;default:'';"
Against an SQLite database with
text_column TEXT NOT NULL COLLATE BINARY DEFAULT ''
Will not generate an alter statement because the default: statement below results in false.
Note the difference between Bool and default vs Time and String.

gorm/migrator/migrator.go

Lines 554 to 569 in 0011f39

	switch field.GORMDataType {
	case schema.Time:
	if !strings.EqualFold(strings.TrimSuffix(dv, "()"), strings.TrimSuffix(field.DefaultValue, "()")) {
	alterColumn = true
	}
	case schema.Bool:
	v1, _ := strconv.ParseBool(dv)
	v2, _ := strconv.ParseBool(field.DefaultValue)
	alterColumn = v1 != v2
	case schema.String:
	if dv != field.DefaultValue && dv != strings.Trim(field.DefaultValue, "'\"") {
	alterColumn = true
	}
	default:
	alterColumn = dv != field.DefaultValue
	}

Bool and default allow the DEFAULT being the same to change a column from being altered to not being altered.
Time and String will mark a column for altering, but NOT remove a column from being altered.

The document you expected this should be explained

https://gorm.io/docs/migration.html#Auto-Migration

Expected answer

If this is working as designed (ie. the DEFAULT on a column is the decider on whether it is altered), then it should be documented as so.