multicorn

pig repo add pgdg -u          # 添加 PGDG 仓库并更新缓存

CREATE EXTENSION multicorn;

from multicorn import ForeignDataWrapper

class MyFDW(ForeignDataWrapper):
    def __init__(self, options, columns):
        super().__init__(options, columns)
        self.options = options
        self.columns = columns

    def execute(self, quals, columns):
        """以字典形式返回行。quals 包含 WHERE 下推信息。"""
        yield {"id": 1, "name": "example"}

    def insert(self, new_values):
        """处理 INSERT 操作。"""
        pass

    def update(self, old_values, new_values):
        """处理 UPDATE 操作。"""
        pass

    def delete(self, old_values):
        """处理 DELETE 操作。"""
        pass

CREATE EXTENSION multicorn;

CREATE SERVER multicorn_srv FOREIGN DATA WRAPPER multicorn
  OPTIONS (wrapper 'myfdw.MyFDW');

CREATE FOREIGN TABLE my_table (
  id integer,
  name text
)
SERVER multicorn_srv
OPTIONS (
  option1 'value1'
);

SELECT * FROM my_table;

CREATE SERVER csv_srv FOREIGN DATA WRAPPER multicorn
  OPTIONS (wrapper 'multicorn.csvfdw.CsvFdw');

CREATE FOREIGN TABLE csvtest (
  col1 text,
  col2 text
)
SERVER csv_srv
OPTIONS (
  filename '/tmp/data.csv',
  skip_header '1',
  delimiter ','
);