Let's say I'm running pg_ctl init or initdb to initialise cluster. When is the exact moment the default database inside this cluster is created?

• In the initdb procedure?
• After I run the server?
• After the first connection to the database?

CodePudding user response：

Quote from the manual

Creating a database cluster consists of creating the directories in which the database data will live, generating the shared catalog tables (tables that belong to the whole cluster rather than to any particular database), and creating the template1 and postgres databases.

^{(emphasis mine)}

So it's created when you run initdb

CodePudding user response：

To see:

/usr/local/pgsql14/bin/initdb -D data/
cd data/
ls -al base/
drwx------  2 postgres users 4096 Feb  9 08:17 1
drwx------  2 postgres users 4096 Feb  9 08:17 13596
drwx------  2 postgres users 4096 Feb  9 08:17 13597

ls -al base/1
total 8304
drwx------ 2 postgres users   4096 Feb  9 08:17 .
drwx------ 5 postgres users   4096 Feb  9 08:17 ..
-rw------- 1 postgres users   8192 Feb  9 08:17 112
-rw------- 1 postgres users   8192 Feb  9 08:17 113
-rw------- 1 postgres users 114688 Feb  9 08:17 1247
-rw------- 1 postgres users  24576 Feb  9 08:17 1247_fsm
-rw------- 1 postgres users   8192 Feb  9 08:17 1247_vm
...

From here [Database File Layout]:

base Subdirectory containing per-database subdirectories

So the 'system' databases are built upon using init(db).