How to create variable with the first day of current month in Databricks Spark Scala?

Question

Using Spark Scala on Databricks, I am trying to create a variable that contains the first day of the current month.

In the first step, I just get the current date, and it works fine:

val current_date = LocalDate.now()

That gives me the correct output, such as:

current_date: java.time.LocalDate = 2022-05-02

My problem is when I try to get the first day of the current month. I have tried to use TemporalAdjuster, but it doesn't work. Can anyone indicate me the correct way to do this?

Examples that I have tried:

val current_month = current_date.temporal(TemporalAdjuster.firstDayOfMonth())

>>> error: value temporal is not a member of java.time.LocalDate
val current_month = current_date.temporal(TemporalAdjuster.firstDayOfMonth())

>>> error: value firstDayOfMonth is not a member of object java.time.temporal.TemporalAdjuster
val current_month = current_date.temporal(TemporalAdjuster.firstDayOfMonth())

val current_month = current_date.with(TemporalAdjuster.firstDayOfMonth())

>>> error: identifier expected but 'with' found.
       val current_month = current_date.with(TemporalAdjuster.firstDayOfMonth())
                                        ^

Answer 1

I just had to use the method withDayOfMonth(1). The 1 inside the brackets indicates that it must return the first day of month.

The following code works:

val current_month = LocalDate.now().withDayOfMonth(1)

Answer 2

Simplest way is to use date_trunc function to round a current date to a given granularity. To get first day, you need to truncate current date to a month level, like this (we need to use to_date because date_trunc returns a timestamp):

to_date(date_trunc( "mon", current_date()))

For example, if you run it as following on Databricks:

display(spark.range(3).withColumn("first_day", 
  to_date(date_trunc( "mon", current_date()))))

you'll get