Calling functions and stored procedures in Snowpark Java¶
To process data in a DataFrame, you can call system-defined SQL functions, user-defined functions, and stored procedures. This topic explains how to call these in Snowpark.
Calling system-defined functions¶
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
static method to call the system-defined function.
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
The following example calls the system-defined function RADIANS, passing in the value from the
// 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();
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:
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
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)¶
Construct a TableFunction object, passing in the name of the table function.
Call the tableFunction method of the Session object, passing in the
TableFunctionobject and a
Mapof 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¶
You can execute a procedure either on the server side (in the Snowflake environment) or locally. Keep in mind that as the two environments are different, the conditions and results of procedure execution may differ between them.
You can call a procedure with the Snowpark API in either of the following ways:
Execute a function locally for testing and debugging using the SProcRegistration.runLocally method.
Execute a procedure in the server-side Snowflake environment using one of the Session.storedProcedure methods. This includes a procedure scoped to the current session or a permanent procedure stored on Snowflake.
You can also call a permanent stored procedure you create with the Snowpark API from SQL code. For more information, refer to Calling a Stored Procedure.
For more on creating procedures with the Snowpark API, refer to Creating stored procedures for DataFrames in Java.
Executing a procedure’s logic locally¶
You can execute the lambda function for your procedure in your local environment using the
The method executes the function and returns its result as the type returned by the function.
For example, you can call a lambda function that you intend to use in a procedure before registering a procedure from it on Snowflake. You
begin by assigning the lambda code as a value to a variable whose type is one of the
interfaces. Using that variable, you can test call the function with the
SProcRegistration.runLocally method. You can also use
the variable to represent the function when registering the procedure.
Code in the following example initializes a
JavaSProc variable from the lambda function that will be the procedure’s logic. It then
tests the function by passing the variable to the
SProcRegistration.runLocally method with the function’s argument. The variable
is also used to register the function.
Session session = Session.builder().configFile("my_config.properties").create(); // Assign the lambda function to a variable. JavaSProc1<Integer, Integer> func = (Session session, Integer num) -> num + 1; // Execute the function locally. int result = (Integer)session.sproc().runLocally(func, 1); System.out.println("\nResult: " + result); // Register the procedure. StoredProcedure sp = session.sproc().registerTemporary( func, DataTypes.IntegerType, DataTypes.IntegerType ); // Execute the procedure on the server. session.storedProcedure(sp, 1).show();
Executing a procedure on the server¶
To execute a procedure in the Snowflake environment on the server, use the
Session.storedProcedure method. The method returns a
For example, you can execute:
A temporary or permanent procedure you create using the Snowpark API.
A procedure created using a CREATE PROCEDURE statement.
Code in the following example creates a temporary procedure designed to execute on the server, but only last for as long as the current Snowpark session. It then executes the procedure using both the procedure’s name and the com.snowflake.snowpark_java.StoredProcedure variable representing it.
Session session = Session.builder().configFile("my_config.properties").create(); String incrementProc = "increment"; // Register the procedure. StoredProcedure tempSP = session.sproc().registerTemporary( incrementProc, (Session session, Integer num) -> num + 1, DataTypes.IntegerType, DataTypes.IntegerType ); // Execute the procedure on the server by passing the procedure's name. session.storedProcedure(incrementProc, 1).show(); // Execute the procedure on the server by passing a variable // representing the procedure. session.storedProcedure(tempSP, 1).show();