教程：复合兴趣计算器运算符

本教程逐步讲解如何为 Lakeflow Designer 创建用于计算复合兴趣的 Python UDF 运算符。 使用此示例可了解转换单个值或列的生成运算符的基础知识。 若要了解详细信息，请参阅 Lakeflow Designer 中的用户定义的运算符。

概述

本教程逐步讲解如何使用 Python UDF 创建用户定义的运算符。 运算符使用复利公式计算投资的未来值， A = P × (1 + r/n)^(n×t)其中：

• P = 主体（起始金额）
• r = 年利率（如十进制）
• n = 每年复合周期数
• t = 以年为单位的时间

步骤 1：编写和测试Python函数

首先，定义执行计算的核心Python函数。 在笔记本单元格中进行测试，以确保其正确运行。

def compound_amount(principal: float,
                    annual_rate: float,
                    compounds_per_year: int,
                    years: float) -> float:
    """
    Compute compound interest future value.

    A = P * (1 + r/n)^(n*t)

    principal: starting amount (P)
    annual_rate: annual nominal rate as decimal (r), e.g. 0.05
    compounds_per_year: compounding periods per year (n), e.g. 12
    years: time in years (t), can be fractional
    """
    import math
    if principal is None or annual_rate is None or compounds_per_year is None or years is None:
        return None

    if compounds_per_year <= 0:
        raise ValueError("compounds_per_year must be > 0")

    return principal * math.pow(1.0 + annual_rate / compounds_per_year,
                                 compounds_per_year * years)

可以使用以下代码测试函数：

# $1,000 invested at 5% annual rate, compounded monthly for 10 years
compound_amount(1000, 0.05, 12, 10)
# Expected result: ~1647.01

步骤 2：为操作员创建 YAML

YAML 配置定义运算符在 Lakeflow Designer 中的显示方式。 对于此运算符：

• Principal 使用 expression 组件，以便用户从其数据中选择一列
• 年利率、每年复利次数和年数使用具有默认值和约束条件的number控件
• 运算符有一个输入端口，该端口为表达式参数提供列数据

schema: user-defined-operator-v0.1.0
type: uc-udf
name: Compound Amount
id: finance.compound_amount
version: '1.0.0'
description: >
  Computes the future value of an investment using compound interest.
  Formula: A = P * (1 + r/n)^(n*t)
config:
  type: object
  properties:
    principal:
      type: string
      format: expression
      title: Principal
      examples:
        - 'Select principal column or expression'
      x-ui:
        widget: expression
        port: in
    annual_rate:
      type: number
      title: Annual rate (decimal)
      default: 0.05
      minimum: 0
      examples:
        - 'e.g. 0.05 for 5%'
      x-ui:
        widget: number
    compounds_per_year:
      type: number
      title: Compounds per year
      default: 12
      minimum: 1
      examples:
        - 'e.g. 12 for monthly'
      x-ui:
        widget: number
    years:
      type: number
      title: Years
      default: 10
      minimum: 0
      examples:
        - 'Time in years (t)'
      x-ui:
        widget: number
  required:
    - principal
    - annual_rate
    - compounds_per_year
    - years
  additionalProperties: false
ports:
  input:
    - name: in
      title: Input
  output:
    - name: out
      title: Output

有关所有可用属性、数据类型、控件和选项的完整指南，请参阅用户定义运算符 YAML 参考。

步骤 3：创建 Unity 目录函数

将 YAML 架构和Python函数合并为单个 CREATE FUNCTION 语句。 YAML 配置位于函数正文开头的 docstring 中。

CREATE OR REPLACE FUNCTION main.my_schema.compound_amount(
    principal DOUBLE,
    annual_rate DOUBLE,
    compounds_per_year INT,
    years FLOAT)
RETURNS DOUBLE
LANGUAGE PYTHON
AS $$
  """
  schema: user-defined-operator-v0.1.0
  type: uc-udf
  name: Compound Amount
  id: finance.compound_amount
  version: "1.0.0"
  description: >
    Computes the future value of an investment using compound interest.
    Formula: A = P * (1 + r/n)^(n*t)
  config:
    type: object
    properties:
      principal:
        type: string
        format: expression
        title: Principal
        examples:
          - "Select principal column or expression"
        x-ui:
          widget: expression
          port: in
      annual_rate:
        type: number
        title: Annual rate (decimal)
        default: 0.05
        minimum: 0
        examples:
          - "e.g. 0.05 for 5%"
        x-ui:
          widget: number
      compounds_per_year:
        type: number
        title: Compounds per year
        default: 12
        minimum: 1
        examples:
          - "e.g. 12 for monthly"
        x-ui:
          widget: number
      years:
        type: number
        title: Years
        default: 10
        minimum: 0
        examples:
          - "Time in years (t)"
        x-ui:
          widget: number
    required:
      - principal
      - annual_rate
      - compounds_per_year
      - years
    additionalProperties: false
  ports:
    input:
      - name: in
        title: Input
    output:
      - name: out
        title: Output
  """

  def compound_amount(principal: float,
                      annual_rate: float,
                      compounds_per_year: int,
                      years: float) -> float:
      import math
      if principal is None or annual_rate is None or compounds_per_year is None or years is None:
          return None

      if compounds_per_year <= 0:
          raise ValueError("compounds_per_year must be > 0")

      return principal * math.pow(1.0 + annual_rate / compounds_per_year,
                                   compounds_per_year * years)

  return compound_amount(principal, annual_rate, compounds_per_year, years)
$$

步骤 4：测试函数

使用 SQL 直接测试 UC 函数：

-- Test 1: $1,000 at 5% compounded monthly for 10 years
SELECT main.my_schema.compound_amount(1000, 0.05, 12, 10)
-- Expected: ~1647.01

-- Test 2: $1,000 at 5% compounded annually for 1 year
SELECT main.my_schema.compound_amount(1000, 0.05, 1, 1)
-- Expected: 1050.00

-- Test 3: $1,000 at 15% compounded monthly for 1 year
SELECT main.my_schema.compound_amount(1000, 0.15, 12, 1)
-- Expected: ~1160.75

步骤 5：注册操作员

将运算符添加到 .user_defined_operators.yaml 文件：

operators:
  - catalog: main
    schema: my_schema
    functionName: compound_amount

步骤 6：设置权限

向需要使用此操作员的用户授予访问权限：

GRANT USE SCHEMA ON SCHEMA main.my_schema TO `<user>`;
GRANT EXECUTE ON FUNCTION main.my_schema.compound_amount TO `<user>`;

在 Lakeflow Designer 中使用运算符

注册后，该操作器会显示在 Lakeflow Designer 中，并具有以下内容：

• 用于从输入数据中选择主体列的下拉列表
• 利率、复利频率和年限的数字输入框（带有合理的默认值）

用户可以应用此运算符来计算整个投资数据列的未来值。