Default encoding is SQL_ASCII

[aanand]

$ docker run -d --name db postgres
fb08c3d5d9081350f8bc4f9de40d7a31f014c3e1c83382bcc9868eff84a42116

$ docker run --link db:db -i -t postgres psql -h db -U postgres
psql (9.3.5)
Type "help" for help.

postgres=# \l
                             List of databases
   Name    |  Owner   | Encoding  | Collate | Ctype |   Access privileges
-----------+----------+-----------+---------+-------+-----------------------
 postgres  | postgres | SQL_ASCII | C       | C     |
 template0 | postgres | SQL_ASCII | C       | C     | =c/postgres          +
           |          |           |         |       | postgres=CTc/postgres
 template1 | postgres | SQL_ASCII | C       | C     | =c/postgres          +
           |          |           |         |       | postgres=CTc/postgres
(3 rows)

Personally, I'd rather it were UTF-8. Thoughts?

[tianon]

I'd tend to agree, but here's the counterargument:

$ docker run -it --rm debian:sid bash
root@95b748d48bdc:/# apt-get update && apt-get install -y postgresql
...
root@95b748d48bdc:/# /etc/init.d/postgresql start
[ ok ] Starting PostgreSQL 9.4 database server: main.
root@95b748d48bdc:/# su - postgres
postgres@95b748d48bdc:~$ psql
psql (9.4beta2)
Type "help" for help.

postgres=# \l
                             List of databases
   Name    |  Owner   | Encoding  | Collate | Ctype |   Access privileges   
-----------+----------+-----------+---------+-------+-----------------------
 postgres  | postgres | SQL_ASCII | C       | C     | 
 template0 | postgres | SQL_ASCII | C       | C     | =c/postgres          +
           |          |           |         |       | postgres=CTc/postgres
 template1 | postgres | SQL_ASCII | C       | C     | =c/postgres          +
           |          |           |         |       | postgres=CTc/postgres
(3 rows)

postgres=# 

[jpetazzo]

I would prefer UTF8 too.

I just re-installed PostgreSQL on my machine; lo and behold:

jpetazzo@tarrasque:~$ sudo -u postgres psql -l
                                  List of databases
   Name    |  Owner   | Encoding |   Collate   |    Ctype    |   Access privileges   
-----------+----------+----------+-------------+-------------+-----------------------
 postgres  | postgres | UTF8     | en_US.UTF-8 | en_US.UTF-8 | 
 template0 | postgres | UTF8     | en_US.UTF-8 | en_US.UTF-8 | =c/postgres          +
           |          |          |             |             | postgres=CTc/postgres
 template1 | postgres | UTF8     | en_US.UTF-8 | en_US.UTF-8 | =c/postgres          +
           |          |          |             |             | postgres=CTc/postgres
(3 rows)

I believe that it defaults to SQL_ASCII, except if you have an UTF-8 locale; then it will default to that. I believe (but that's not backed by any hard data; just anecdotal experience) that everybody will use some kind of local locale, and that the vast majority (for some definition of "vast") of the installs out there will therefore have UTF8.

Now, to give you a more specific example: during the Docker training, we show an example involving Docker running a Rails app with a PostgreSQL backend. We are updating this to use the canon postgres image instead of our hackish training/postgres image; however, Rails complains because the DB is "only" SQL_ASCII. I'm trying to work around the issue by specifying the encoding in the database.yml; but it would be nice if it could work out of the box for most people.

[tianon]

Hmm, maybe it's based on LANG, even for the default install? We have C.UTF-8 in the base images, so it shouldn't be a "do you have UTF-8; ok we'll use it" issue, but it might be. Maybe we need to locale-gen en_US.UTF-8 in this image. Thanks for doing more testing on this, @jpetazzo!