CREATE FUNCTION

您可以通过指定函数名称、输入和输出数据类型来创建或替换 JavaScript UDF。 Please check the mapping of data types for input and output.

The following example defines a new function test_add_five_5:

CREATE OR REPLACE FUNCTION test_add_five_5(value float32)
RETURNS float32
LANGUAGE JAVASCRIPT AS $$
  function test_add_five_5(values) {
    for(let i=0;i<values.length;i++) {
      values[i]=values[i]+5;
    }
    return values;
  }
$$;

备注：

Line 1: the function is to be created with name test_add_five_5, taking a single float32 parameter.
Line 2: the function is to return a float32
Line 4: the same function name is defined in the code block. To improve performance, multiple UDF calls will be batched. The value is actually an array of float 为了提高性能，将对多个 UDF 调用进行批处理。 The values is an array of float
第 5 行和第 6 行：迭代输入数组并将每个值加 5
Line 8: return an array of new values as return type
第 10 行：关闭代码块。

注意

In Timeplus Enterprise, you can add debug information via console.log(..) in the JavaScript UDF. The logs will be available in the server log files.

创建聚合函数

创建用户定义聚合函数 (UDAF) 需要更多的精力。 Please check this documentation for the 3 required and 3 optional functions.

CREATE AGGREGATE FUNCTION test_sec_large(value float32)
RETURNS float32
LANGUAGE JAVASCRIPT AS $$
    {
      initialize: function() {
         this.max = -1.0;
         this.sec = -1.0
      },
      process: function(values) {
        for (let i = 0; i < values.length; i++) {
          if (values[i] > this.max) {
            this.sec = this.max;
            this.max = values[i]
          }
          if (values[i] < this.max && values[i] > this.sec)
            this.sec = values[i];
        }
      },
            finalize: function() {
            return this.sec
            },
            serialize: function() {
            let s = {
            'max': this.max,
            'sec': this.sec
            };
        return JSON.stringify(s)
      },
        deserialize: function(state_str) {
                                           let s = JSON.parse(state_str);
                                           this.max = s['max'];
                                           this.sec = s['sec']
        },
        merge: function(state_str) {
                                     let s = JSON.parse(state_str);
                                     if (s['sec'] >= this.max) {
                                     this.max = s['max'];
                                     this.sec = s['sec']
                                     } else if (s['max'] >= this.max) {
                                     this.sec = this.max;
                                     this.max = s['max']
                                     } else if (s['max'] > this.sec) {
                                     this.sec = s['max']
                                     }
                                     }
        }
$$;

CREATE FUNCTION​

创建聚合函数​

CREATE FUNCTION

创建聚合函数