Export Query Result as CSV file from Docker PostgreSQL container to local machine

Question

I'm not sure if this is possible of if I'm doing something wrong since I'm still pretty new to Docker. Basically, I want to export a query result inside PostgreSQL docker container as a csv file to my local machine.

This is where I got so far. Firstly, I run my PostgreSQL docker container with this command:

sudo docker run --rm --name pg-docker -e POSTGRES_PASSWORD=something -d -p 5432:5432 -v $HOME/docker/volumes/postgres:/var/lib/postgresql/data postgres

Then I access the docker container with docker exec to run PostgreSQL command that would copy the query result to a csv file with specified location like this:

\copy (select id,value from test) to 'test_1.csv' with csv;

I thought that should export the query result as a csv file named test_1.csv in the local machine, but I couldn't find the file anywhere in my local machine, also checked both of these directories: $HOME/docker/volumes/postgres ; /var/lib/postgresql/data postgres

Answer 1

您可以将数据导出到STDOUT并将结果通过管道传输到客户端计算机中的文件：

$ docker exec -it pgdocker psql "COPY (SELECT * FROM test) TO STDOUT CSV" > test_1.csv

Answer 2

The /var/lib/postgresql/data directory is where the database server stores its data files. It isn't a directory that users need to manipulate directly or where nothing interesting can be found.

Paths like test_1.csv are relative to working directory. The default directory when you enter the postgres container with docker exec is / so that's where your file should be. You can also switch to another directory with cd before running psql :

root@b9e5a0572207:/some/other/path# cd /some/other/path/
root@b9e5a0572207:/some/other/path# psql -U postgres

... or you can provide an absolute path:

\copy (select id,value from test) to '/some/other/path/test_1.csv' with csv;

You can use docker cp to transfer a file from the container to the host:

docker cp pg-docker:/some/other/path/test_1.csv /tmp

... or you can create a volume if this is something you do often.