Cross Join for calculation in Spark SQL

Question

I have a temporary view with only 1 record/value and I want to use that value to calculate the age of the customers present in another big table (with 100

Answer 1

Inside view you are using constant value, You can simply put same value in below query without cross join.

select 
a.custid, 
a.birthdt, 
cast((datediff(to_date('10-05-2020', 'dd-MM-yyyy'), a.birthdt)/365.25) as int) as age
from cust a;

scala> spark.sql("select * from cust").show(false)
+------+----------+
|custid|birthdt   |
+------+----------+
|A1234 |1980-03-20|
|B3456 |1985-05-09|
|C2356 |1990-12-15|
+------+----------+

scala> spark.sql("select a.custid, a.birthdt, cast((datediff(to_date('10-05-2020', 'dd-MM-yyyy'), a.birthdt)/365.25) as int) as age from cust a").show(false)
+------+----------+---+
|custid|birthdt   |age|
+------+----------+---+
|A1234 |1980-03-20|40 |
|B3456 |1985-05-09|35 |
|C2356 |1990-12-15|29 |
+------+----------+---+

Answer 2

Hard to work out exactly your point, but if you cannot use Scala or pyspark and dataframes with .cache etc. then I think that instead of of using a temporary view, just create a single row table. My impression is you are using Spark %sql in a notebook on, say, Databricks.

This is my suspicion as it were.

That said a broadcastjoin hint may well mean the optimizer only sends out 1 row. See https://jaceklaskowski.gitbooks.io/mastering-spark-sql/content/spark-sql-hint-framework.html#specifying-query-hints

Answer 3

Simply use withColumn!

df.withColumn("new_col", lit("10-05-2020").cast("date"))