PostgreSQL pg_clickhouse插件的安装和使用

clickhouse公司开发的pg_clickhouse可以由PostgreSQL数据库调用clickhouse数据库的能力，实现快速的查询。

我按照pg_clickhouse文档的提示，完成了docker镜像下载、容器的运行等步骤。

1. docker镜像下载
   文档中的命令行是

docker pull ghcr.io/clickhouse/pg_clickhouse:18-0.1.0

国内用官方地址下载较慢，还容易中断。可以用南京大学镜像快速下载。

docker pull ghcr.nju.edu.cn/clickhouse/pg_clickhouse:18-0.1.0
Trying to pull ghcr.nju.edu.cn/clickhouse/pg_clickhouse:18-0.1.0...
Getting image source signatures
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Writing manifest to image destination
Storing signatures
5cb0431c686e00a8fb24d4a5c80d3102bcbab366c5a2e1da2e9d344477e3b006

2. 运行容器
   首次运行用docker run命令，并创建插件。

docker run --name pg_clickhouse -e POSTGRES_PASSWORD=my_pass -d ghcr.nju.edu.cn/clickhouse/pg_clickhouse:18
docker exec -it pg_clickhouse psql -U postgres -c 'CREATE EXTENSION pg_clickhouse'

以后再次运行，只要docker start启动容器，docker exec -it登录即可

docker start pg_clickhouse
pg_clickhouse

docker exec -it pg_clickhouse psql -U postgres
psql (18.1 (Debian 18.1-1.pgdg13+2))
Type "help" for help.

postgres=# CREATE SERVER taxi_srv FOREIGN DATA WRAPPER clickhouse_fdw
       OPTIONS(driver 'binary', host 'localhost', dbname 'taxi');
CREATE SERVER
postgres=# CREATE USER MAPPING FOR CURRENT_USER SERVER taxi_srv
       OPTIONS (user 'default');
CREATE USER MAPPING
postgres=# CREATE SCHEMA taxi;
CREATE SCHEMA
postgres=# IMPORT FOREIGN SCHEMA taxi FROM SERVER taxi_srv INTO taxi;
ERROR:  pg_clickhouse: connection error: fail to connect: Connection refused

前几步都没有报错，导入SCHEMA报错了，应该是缺少一个运行中的clickhouse服务器。