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Create a User-Defined Function

  • Capella Operational
  • how-to
    +
    Create a user-defined function (UDF) to call an inline function or a specific JavaScript function stored in a library.

    For more information about how to create a UDF library, see Create a User-Defined Function Library.

    Prerequisites

    • If you want to use cbq to create your user-defined function, you must complete the prerequisites for using cbq. For more information, see Prerequisites.

    • If you want to use libraries to organize your user-defined functions, you need to create a UDF library and add a JavaScript function. For more information, see Create a User-Defined Function Library.

    Create a User-Defined Function From a UDF Library

    To create a user-defined function that references a JavaScript function from a UDF library:

    • Use the Query Tab.

    • Use the SQL++ CREATE FUNCTION statement, and reference the UDF library and JavaScript function.

    • Query Tab

    • SQL++

    1. On the Operational Clusters page, select the operational cluster where you want to create a user-defined function from a UDF library.

    2. Go to Data Tools  Query.

    3. In the Data Insights area, to the left of the query editor, find the Functions section.

    4. Next to the Functions section header, go to Create (+)  Function.

    5. In the Function Name field, enter a name for your function.

    6. Choose the access level for your user-defined function:

      1. Choose Global to allow all buckets and scopes on this cluster to use this function.

      2. Choose Specific to choose a specific bucket and scope on this cluster that can use this function.

        Choose the same access level and namespace as your UDF library for your user-defined function. Your function name must be unique in your selected namespace. Users must set this bucket and scope as their query context to use this function later.

    7. In the Parameters field, enter a list of parameters, separated by commas (,) for any values you need to process or use in your function.

      For example, if you created a JavaScript function that has a variable named a, you should add a parameter a.

      If you want to create a user-defined function that can take a variable length list of parameters, rather than a comma separated list of parameters, add …​ as a parameter. Your function will accept an array of values as a parameter, and assign each value it receives to the named variables in your function.

    8. Click the UDF Library tab.

    9. Choose the UDF library and specific JavaScript function you want to assign to this user-defined function.

    10. Click Create Function.

    Execute a CREATE FUNCTION statement in cbq to create a user-defined function:

    CREATE FUNCTION default:`travel-sample`.`inventory`.GetBusinessDays(...) LANGUAGE JAVASCRIPT as "getBusinessDays" AT "travel-sample/inventory/my-library";
    Set the same namespace as your UDF library for your user-defined function. Your function name must be unique in your selected namespace. Users must set this bucket and scope as their query context to use this function later.

    For more information on the CREATE FUNCTION statement, see CREATE FUNCTION.

    Create an Inline User-Defined Function

    To create a user-defined function that uses inline JavaScript or SQL++:

    • Query Tab

    • SQL++

    1. On the Operational Clusters page, select the operational cluster where you want to create a user-defined function.

    2. Go to Data Tools  Query.

    3. In the Data Insights area, to the left of the query editor, find the Functions section.

    4. Next to the Functions section header, go to Create (+)  Function.

    5. In the Function Name field, enter a name for your function.

    6. Choose the access level for your user-defined function:

      1. Choose Global to allow all buckets and scopes on this cluster to use this function.

      2. Choose Specific to choose a specific bucket and scope on this cluster that can use this function.

        Your function name must be unique in your selected namespace. Users must set this bucket and scope as their query context to use this function later.

    7. In the Parameters field, enter a list of parameters, separated by commas (,) for any values you need to process or use in your function.

      For example, if you created a JavaScript function that has a variable named a, you should add a parameter a.

      If you want to create a user-defined function that can take a variable length list of parameters, rather than a comma separated list of parameters, add …​ as a parameter. Your function will accept an array of values as a parameter, and assign each value it receives to the named variables in your function. You can also define your function with a variable length parameter list, by adding a variable to your function definition that starts with …​ - such as …​ args.

    8. Click the Inline SQL++ or Inline JavaScript tab.

    9. Enter a SQL++ expression or JavaScript function.

    10. Click Create Function.

    Execute a CREATE FUNCTION statement in cbq to create an inline user-defined function:

    Inline JavaScript
    CREATE FUNCTION celsius(...) LANGUAGE INLINE AS (args[0] - 32) * 5/9;
    Inline SQL++
    CREATE FUNCTION locations(vActivity) { (
  SELECT id, name, address, city
  FROM landmark
  WHERE activity = vActivity) };

    You cannot create 2 functions with the same name inside the same namespace.

    For more information about the CREATE FUNCTION statement, see CREATE FUNCTION.

    Next Steps