Hello! After updating to newest version of exposed...

# exposed

[Rafał Kuźmiński]

Hello! After updating to newest version of exposed (ColumnType changes) my custom abs() function is not working for nullable columns. I tried to create other method for nullable type, but I have no idea how to make it compile.

Default version

class Abs<T : Number>(
    val expr: Expression<T>,
    columnType: IColumnType<T>
) : Function<T>(columnType), WindowFunction<T?> {
    override fun toQueryBuilder(queryBuilder: QueryBuilder): Unit = queryBuilder { append("ABS(", expr, ")") }

    override fun over(): WindowFunctionDefinition<T?> {
        return WindowFunctionDefinition(columnType, this)
    }
}

fun <T : Number> ExpressionWithColumnType<T>.abs() = Abs(this, this.columnType)

My experiment with nullable type:

class AbsNullable<T : Number?>(
    val expr: Expression<T>,
    columnType: IColumnType<T>
) : Function<T>(columnType), WindowFunction<T?> {
    override fun toQueryBuilder(queryBuilder: QueryBuilder): Unit = queryBuilder { append("ABS(", expr, ")") }

    override fun over(): WindowFunctionDefinition<T?> {
        return WindowFunctionDefinition(columnType, this)
    }
}

fun <T : Number?> ExpressionWithColumnType<T>.abs() = AbsNullable(this, this.columnType)

But compiler throws error for columnType like on screenshot

Do you have any ideas how to configure functions for nullable columns? Or maybe is there built in function for absolute value in exposed?

[Chantal Loncle]

Hi @Rafał Kuźmiński There are quite a few built-in classes available for math functions and trigonometric functions, one of which is AbsFunction. But these classes are not set up to implement the WindowFunction interface, which you seem to need.

This single function class works with both nullable and non-nullable columns for me:

class Abs<T : Number?>(
    val expr: Expression<T>,
    columnType: IColumnType<T & Any>
) : Function<T?>(columnType), WindowFunction<T?> {
    override fun toQueryBuilder(
        queryBuilder: QueryBuilder
    ) { queryBuilder { append("ABS(", expr, ")") } }

    override fun over(): WindowFunctionDefinition<T?> {
        return WindowFunctionDefinition(columnType, this)
    }
}

fun <T : Number?> ExpressionWithColumnType<T>.abs(): Abs<T> = Abs(this, this.columnType)

Alternatively you could take a look at how our Min and Max classes are implemented.