Calling Functions and Stored Procedures in Snowpark Java¶

Calling System-Defined Functions¶

If you need to call system-defined SQL functions, use the equivalent static methods in the Functions class.

The following example calls the upper static method in the Functions class (the equivalent of the system-defined UPPER function) to return the values in the name column with the letters in uppercase:

DataFrame df = session.table("sample_product_data");
df.select(Functions.upper(Functions.col("name"))).show();

If a system-defined SQL function is not available in the Functions class, you can use the Functions.callUDF static method to call the system-defined function.

For callUDF, pass the name of the system-defined function as the first argument. If you need to pass the values of columns to the system-defined function, define and pass Column objects as additional arguments to the callUDF method.

The following example calls the system-defined function RADIANS, passing in the value from the column degrees:

// Call the system-defined function RADIANS() on degrees.
DataFrame dfDegrees = session.range(0, 360, 45).rename("degrees", Functions.col("id"));
dfDegrees.select(Functions.col("degrees"), Functions.callUDF("radians", Functions.col("degrees"))).show();

The callUDF method returns a Column, which you can pass to the DataFrame transformation methods (e.g. filter, select, etc.).

Calling Scalar User-Defined Functions (UDFs)¶

The method for calling a UDF depends on how the UDF was created:

• To call an anonymous UDF, call the apply method of the UserDefinedFunction object that was returned when you created the UDF.

  The arguments that you pass to a UDF must be Column objects. If you need to pass in a literal, use Functions.lit(), as explained in Using Literals as Column Objects.

• To call UDFs that you registered by name and UDFs that you created by executing CREATE FUNCTION, use the Functions.callUDF static method.

  Pass the name of the UDF as the first argument and any UDF parameters as additional arguments.

Calling a UDF returns a Column object containing the return value of the UDF.

The following example calls the UDF function doubleUdf, passing in the value from the columns quantity. The example passes the return value from doubleUdf to the select method of the DataFrame.

import com.snowflake.snowpark_java.types.*;
...
// Create and register a temporary named UDF
// that takes in an integer argument and returns an integer value.
UserDefinedFunction doubleUdf =
  session
    .udf()
    .registerTemporary(
      "doubleUdf",
      (Integer x) -> x + x,
      DataTypes.IntegerType,
      DataTypes.IntegerType);
// Call the named UDF, passing in the "quantity" column.
// The example uses withColumn to return a DataFrame containing
// the UDF result in a new column named "doubleQuantity".
DataFrame df = session.table("sample_product_data");
DataFrame dfWithDoubleQuantity = df.withColumn("doubleQuantity", doubleUdf.apply(Functions.col("quantity")));
dfWithDoubleQuantity.show();

Calling Table Functions (System Functions and UDTFs)¶

To call a table function or a user-defined table function (UDTF):

1. Construct a TableFunction object, passing in the name of the table function.

2. Call the tableFunction method of the Session object, passing in the TableFunction object and a Map of input argument names and values.

table?Function returns a DataFrame that contains the output of the table function.

For example, suppose that you executed the following command to create a SQL UDTF:

CREATE OR REPLACE FUNCTION product_by_category_id(cat_id INT)
  RETURNS TABLE(id INT, name VARCHAR)
  AS
  $$
    SELECT id, name
      FROM sample_product_data
      WHERE category_id = cat_id
  $$
  ;

The following code calls this UDTF and creates a DataFrame for the output of the UDTF. The example prints the first 10 rows of output to the console.

import java.util.HashMap;
import java.util.Map;
...

Map<String, Column> arguments = new HashMap<>();
arguments.put("cat_id", Functions.lit(10));
DataFrame dfTableFunctionOutput = session.tableFunction(new TableFunction("product_by_category_id"), arguments);
dfTableFunctionOutput.show();

If you need to join the output of a table function with a DataFrame, call the join method that passes in a TableFunction.

Calling Stored Procedures¶

To call a stored procedure, use the sql method of the Session class. See Executing SQL Statements.