Function¶

Creating a Function (CREATE FUNCTION)¶

To start a CREATE FUNCTION query, use createFunction in SchemaBuilder:

import static com.datastax.oss.driver.api.querybuilder.SchemaBuilder.*;

CreateFunctionStart create = createFunction("log");

Like all other CREATE queries, one may supply ifNotExists() to require that the UDF should only be created if it doesn’t already exist, i.e.:

CreateFunctionStart create = createFunction("cycling", "log").ifNotExists();

You may also specify that you would like to replace an existing function by the same signature if it exists. In this case, use orReplace:

CreateFunctionStart create = createFunction("cycling", "log").orReplace();

One may also specify the parameters of a function using withParameter:

createFunction("cycling", "left")
    .withParameter("colName", DataTypes.TEXT)
    .withParameter("num", DataTypes.DOUBLE)

There are a number of steps that must be executed to complete a function:

• Specify whether the function is called on null input (calledOnNull) or if it should simply return null (returnsNullOnNull).

• Specify the return type of the function using returnsType

• Specify language of the function body using withJavaLanguage, withJavaScriptLanguage, or withLanguage

• Specify the function body with as or asQuoted

For example, the following defines a complete CREATE FUNCTION statement:

createFunction("cycling", "log")
    .withParameter("input", DataTypes.DOUBLE)
    .calledOnNull()
    .returnsType(DataTypes.DOUBLE)
    .withJavaLanguage()
    .asQuoted("return Double.valueOf(Math.log(input.doubleValue()));");

// CREATE FUNCTION cycling.log (input double) CALLED ON NULL INPUT RETURNS double LANGUAGE java
// AS 'return Double.valueOf(Math.log(input.doubleValue()));'

The as method expects an already quoted function body. Use asQuoted to quote it automatically. Bodies containing single quotes use the $$ delimiter, as long as the body does not also contain $$. Otherwise, the builder surrounds the body with single quotes and escapes each embedded single quote by doubling it. For example:

createFunction("sayhi")
    .withParameter("input", DataTypes.TEXT)
    .returnsNullOnNull()
    .returnsType(DataTypes.TEXT)
    .withJavaScriptLanguage()
    .asQuoted("'hi ' + input;");
// CREATE FUNCTION sayhi (input text) RETURNS NULL ON NULL INPUT RETURNS text
// LANGUAGE javascript AS $$ 'hi ' + input; $$

For a body containing both delimiters, such as return "O'Reilly $$";, asQuoted produces 'return "O''Reilly $$";'.

Dropping a Function (DROP FUNCTION)¶

To create a DROP FUNCTION query, use dropFunction:

dropFunction("cycling", "log");
// DROP FUNCTION cycling.log

You may also specify ifExists:

dropFunction("log").ifExists();
// DROP FUNCTION IF EXISTS log