How do I apply `NOW()` as datetime column value in Kotlin Exposed? - kotlin-exposed

Question

In PostgreSQL I have a table with a column of the timestamp type. I hope this maps to a Kotlin Exposed data type of datetime (docs are unclear, but that's another question).
My question now is: how do I update/insert a value with the SQL literal NOW(), so that the timestamp is set to the current timestamp by the database server?
I'm currently trying to apply this in the Exposed DSL API like this:
object MyTable : Table() {
val col1: Column<String> = varchar("col1", 100).primaryKey()
val last_update: Column<DateTime?> = datetime("last_update").nullable()
}
MyTable.update ({ MyTable.col1 eq "abcd1234" }) {
// How do I put a literal 'NOW()' here?
it[MyTable.last_update] = ...
}
I found a way to declare a custom Expression in the Exposed source code, like this:
val nowExpression = object : Expression<DateTime>() {
override fun toSQL(queryBuilder: QueryBuilder) = "NOW()"
}
But how do I apply that in my update/insert statement?
Kotlin unit tests I found:
Use Kotlin-side of DateTime.now() (not what I want), or
Use a column default value of now, then omitting the column value in the insert. This is where I found the literal NOW() expression. However, I want to keep my default to NULL on that column.
I did not find a unit test to apply a custom expression in a DSL insert/update, but perhaps I am missing something.

Answer 1

There is update function on Insert/Update statements which accepts Expression.
MyTable.update ({ MyTable.col1 eq "abcd1234" }) {
it.update(MyTable.last_update, nowExpression)
}