pg_clickhouse插件，在postgresql中借助clickhouse借用OLAP能力

pg_clickhouse官方文档
clickhouse官方文档
postgresql_fdw文档

1. 启动

docker compose文件内容或者执行下载项目
pg_clickhouse的 clickhouse样例地址

services:
  pg_clickhouse:
    image: ghcr.io/clickhouse/pg_clickhouse:18
    container_name: pg_clickhouse
    environment:
      POSTGRES_PASSWORD: my_pass
    ports:
      - "15432:5432"
    restart: unless-stopped
    depends_on:
      - clickhouse
    volumes:
      - ./init:/docker-entrypoint-initdb.d

  clickhouse:
    image: clickhouse/clickhouse-server:24.8.9.95
    container_name: clickhouse
    ports:
      - "18123:8123"
      - "19000:9000"
    restart: unless-stopped

docker compose up -d

2. clickhouse 数据库表创建,数据初始化

CREATE DATABASE IF NOT EXISTS taxi;

CREATE TABLE taxi.trips
(
    trip_id UInt32,
    vendor_id Enum8(
        '1'      =  1, '2'      =  2, '3'      =  3, '4'      =  4,
        'CMT'    =  5, 'VTS'    =  6, 'DDS'    =  7, 'B02512' = 10,
        'B02598' = 11, 'B02617' = 12, 'B02682' = 13, 'B02764' = 14,
        ''       = 15
    ),
    pickup_date Date,
    pickup_datetime DateTime,
    dropoff_date Date,
    dropoff_datetime DateTime,
    store_and_fwd_flag UInt8,
    rate_code_id UInt8,
    pickup_longitude Float64,
    pickup_latitude Float64,
    dropoff_longitude Float64,
    dropoff_latitude Float64,
    passenger_count UInt8,
    trip_distance Float64,
    fare_amount Decimal(10, 2),
    extra Decimal(10, 2),
    mta_tax Decimal(10, 2),
    tip_amount Decimal(10, 2),
    tolls_amount Decimal(10, 2),
    ehail_fee Decimal(10, 2),
    improvement_surcharge Decimal(10, 2),
    total_amount Decimal(10, 2),
    payment_type Enum8('UNK' = 0, 'CSH' = 1, 'CRE' = 2, 'NOC' = 3, 'DIS' = 4),
    trip_type UInt8,
    pickup FixedString(25),
    dropoff FixedString(25),
    cab_type Enum8('yellow' = 1, 'green' = 2, 'uber' = 3),
    pickup_nyct2010_gid Int8,
    pickup_ctlabel Float32,
    pickup_borocode Int8,
    pickup_ct2010 String,
    pickup_boroct2010 String,
    pickup_cdeligibil String,
    pickup_ntacode FixedString(4),
    pickup_ntaname String,
    pickup_puma UInt16,
    dropoff_nyct2010_gid UInt8,
    dropoff_ctlabel Float32,
    dropoff_borocode UInt8,
    dropoff_ct2010 String,
    dropoff_boroct2010 String,
    dropoff_cdeligibil String,
    dropoff_ntacode FixedString(4),
    dropoff_ntaname String,
    dropoff_puma UInt16
)
ENGINE = MergeTree
PARTITION BY toYYYYMM(pickup_date)
ORDER BY pickup_datetime;


-- 导入数据
INSERT INTO taxi.trips
SELECT * FROM s3(
    'https://datasets-documentation.s3.eu-west-3.amazonaws.com/nyc-taxi/trips_{1..2}.gz',
    'TabSeparatedWithNames', "
    trip_id UInt32,
    vendor_id Enum8(
        '1'      =  1, '2'      =  2, '3'      =  3, '4'      =  4,
        'CMT'    =  5, 'VTS'    =  6, 'DDS'    =  7, 'B02512' = 10,
        'B02598' = 11, 'B02617' = 12, 'B02682' = 13, 'B02764' = 14,
        ''       = 15
    ),
    pickup_date Date,
    pickup_datetime DateTime,
    dropoff_date Date,
    dropoff_datetime DateTime,
    store_and_fwd_flag UInt8,
    rate_code_id UInt8,
    pickup_longitude Float64,
    pickup_latitude Float64,
    dropoff_longitude Float64,
    dropoff_latitude Float64,
    passenger_count UInt8,
    trip_distance Float64,
    fare_amount Decimal(10, 2),
    extra Decimal(10, 2),
    mta_tax Decimal(10, 2),
    tip_amount Decimal(10, 2),
    tolls_amount Decimal(10, 2),
    ehail_fee Decimal(10, 2),
    improvement_surcharge Decimal(10, 2),
    total_amount Decimal(10, 2),
    payment_type Enum8('UNK' = 0, 'CSH' = 1, 'CRE' = 2, 'NOC' = 3, 'DIS' = 4),
    trip_type UInt8,
    pickup FixedString(25),
    dropoff FixedString(25),
    cab_type Enum8('yellow' = 1, 'green' = 2, 'uber' = 3),
    pickup_nyct2010_gid Int8,
    pickup_ctlabel Float32,
    pickup_borocode Int8,
    pickup_ct2010 String,
    pickup_boroct2010 String,
    pickup_cdeligibil String,
    pickup_ntacode FixedString(4),
    pickup_ntaname String,
    pickup_puma UInt16,
    dropoff_nyct2010_gid UInt8,
    dropoff_ctlabel Float32,
    dropoff_borocode UInt8,
    dropoff_ct2010 String,
    dropoff_boroct2010 String,
    dropoff_cdeligibil String,
    dropoff_ntacode FixedString(4),
    dropoff_ntaname String,
    dropoff_puma UInt16
") SETTINGS input_format_try_infer_datetimes = 0;

3. 验证数据和服务正常

clickhouse查看表数量

SELECT count() FROM taxi.trips;

4. postgresql执行链接配置

-- 启用 pg_clickhouse 扩展
CREATE EXTENSION IF NOT EXISTS pg_clickhouse;

-- 创建 ClickHouse 外部服务器
CREATE SERVER IF NOT EXISTS taxi_srv
FOREIGN DATA WRAPPER clickhouse_fdw
OPTIONS (
host 'clickhouse',  -- ClickHouse 服务名（与 docker-compose.yml 一致）
port '8123'         -- ClickHouse HTTP 端口
);

-- 映射 PostgreSQL 用户到 ClickHouse 用户
CREATE USER MAPPING IF NOT EXISTS FOR CURRENT_USER
SERVER taxi_srv
OPTIONS (
user 'default',     -- ClickHouse 用户名
password ''         -- 密码为空（如有密码请修改）
);

5. 创建 schema映射外部clickhouse表

-- 创建 schema
CREATE SCHEMA IF NOT EXISTS taxi;

-- 导入表
IMPORT FOREIGN SCHEMA taxi FROM SERVER taxi_srv INTO taxi;

6. 查询验证

SELECT round(avg(tip_amount), 2) FROM taxi.trips;

注意

• 避免 SELECT *：明确指定所需列，减少数据传输开销
• 数据类型兼容：关联查询时需确保字段类型一致（如用 toUInt64 转换）
• 字典优势：ClickHouse 字典是内存维度表，关联性能优于普通 JOIN
• 查询下推：复杂查询用 EXPLAIN 验证是否完全下推，避免本地计算
• 会话设置：可通过 SET pg_clickhouse.session_settings = 'join_use_nulls 1, final 1' 配置 ClickHouse 会话参数

参考博客