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This video demonstrates how to switch a Ruby on Rails application's database from SQLite to PostgreSQL by updating configuration files, installing and configuring PostgreSQL (including setting up user roles), and running the necessary Rails commands for production deployment.
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Right, so guys,
0:00
the next step on my agenda is to change
our database from SQLite to PostgreSQL.
0:00
Now, SQLite is the database that all
Rails' applications use by default.
0:05
But if I go to config, and
then I go to database.yml,
0:08
we can see that here it
says the adapter is SQLite.
0:13
SQLite is a great database.
0:17
However, it's not suitable for production.
0:19
And I'm going to switch to PostgreSQL
because that's what we're going to use to
0:21
deploy with Kamal.
0:24
And so, we need to switch to
PostgreSQL for that to actually work.
0:25
So, two different things that you need
to know is that SQLite is used for
0:28
development and PostgreSQL is
generally used for production.
0:31
PostgreSQL has greater capabilities and
it's a larger database.
0:34
If you don't know what I'm saying,
I'm saying it's PostgreSQL,
0:37
if you've never heard of it before.
0:40
PostgreSQL, right here.
0:42
Okay, so let's get started.
0:43
The first thing I'm gonna
do is stop the server.
0:45
I'm going to use the Windows key and
the arrow buttons to put it over there so
0:46
you can see it.
0:50
Then the first command we're going to
run is called rails db:system:change,
0:50
and then it's going to be, to=postgresql.
0:57
Now, this is kind of a simpler way of
changing our system to PostgreSQL.
1:00
And it's just going to change
this database.yml file.
1:04
If I just make this full screen so
you can see it a little bit better.
1:07
So you're gonna change
the adapter to PostgreSQL, and
1:10
it will do some other things as well
in the other configuration files.
1:12
So hit Enter on that command.
1:15
We are going to overwrite, so hit y.
1:17
And now it's done.
1:19
So as you can see, it added the Gem,
it forced database.yml file to change, and
1:20
it added some stuff to the docker file.
1:25
Next, we need to install
PostgreSQL on our Linux subsystem.
1:27
So to do that, we're going to hit clear,
just so we can clear it.
1:30
And we can make it clear.
1:32
And we're first going to run the command,
sudo apt update.
1:34
This command updates everything on
our Linux subsystem for Windows.
1:37
And as you can see, now it is done, and
14 packages have been upgraded, it says.
1:41
Next, we're actually going
to install Postgres, and
1:45
this might take a while if you don't
have it already, so be prepared.
1:47
So the command is sudo apt install
postgresql postgresql-contrib.
1:51
So hit Enter on that command.
1:58
And as you can see it says,
postgresql is already the newest version.
2:00
And that's because I already
have Postgres on this machine.
2:03
But for you, it will just install it and
it might take a few seconds.
2:05
So the next command is actually going
to ensure that the service of Postgres
2:08
is started on the machine.
2:11
So the next command is sudo
systemctl start, of course,
2:13
because we're gonna start it,
postgresql.service.
2:17
So it's all fairly simple to understand.
2:22
I think we get it, right?
2:24
So hit Enter on that command,
and now it's started.
2:25
So now that Postgres is installed, we need
to connect Ruby on Rails to Postgres.
2:28
First of all, you need to know that any
Ruby on Rails app tries to connect to
2:31
Postgres using a role.
2:35
By default,
this role is the main user of your PC.
2:36
So in my case, it would be Mal, M-A-L.
2:39
This word right here, Mal.
2:43
Now, when Postgres is installed,
2:44
it automatically creates
a role called Postgres.
2:46
But we need to create a role called Mal,
or whatever you called your PC.
2:48
So let's go ahead and do that.
2:52
So in our terminal we're gonna hit
clear again, just to make it clearer.
2:53
So we're going to run
the Postgres commands now.
2:57
So, sudo -i -u postgres.
2:59
Hit Enter.
3:02
And as you can see, now we're
actually logged in as the role or
3:03
the user, called postgres.
3:07
Because with Postgres there are many
different users, kinda like a Windows PC,
3:08
you can have different users,
but this is just a database.
3:12
So now we're gonna create a user
called the original user of our PC.
3:15
Now we're gonna create a user called Mal,
and that way Ruby on Rails will
3:19
automatically connect because it is
expecting our role to be called Mal.
3:23
So now we are logged in as the default
Postgres user, and we can create a new
3:26
role called Mal, in my case, so
that Rails can connect to Postgres easily.
3:30
So we're gonna run the command,
createuser --interactive.
3:34
So as you can see,
this script prompts us with some choices.
3:39
We have to enter the name
of the role to add.
3:41
Of course, my case is gonna be mal.
3:43
But for you it's most likely
definitely not going to be mal, so
3:45
make sure to check up here while it is.
3:49
And then you have to put this one in here,
pretty much.
3:51
So in your case,
it'll be whatever you named your PC.
3:54
If you haven't named your PC,
it might be something different.
3:56
The name of the role must be your
default username on your PC.
3:59
In my case Mal,
your username will probably not be Mal.
4:02
Hit Enter, and as you can see, it says,
shall the new role be a super user?
4:05
And we're going to say yes, because it
must be a super user to create databases.
4:08
So hit yes, type yes.
4:12
Now it says, error: creation of the role,
mal already exists.
4:14
So that means that mal already exists,
and I'm fine.
4:18
But you need to actually create that role.
4:20
And if it says already exists,
then you're good too.
4:21
Now that we've done that,
we're going to actually hit exit, and
4:23
then we're going to run the command
called rails db:create.
4:26
And if that works,
then we've done everything successfully.
4:29
Now it says, could not find gem
pg in locally installed gems.
4:32
This is the common error we'll run into,
we don't have the gem.
4:35
So just run, bundle install,
4:37
which we forgot to run earlier after
we ran the Rails DB system change.
4:39
So now that we've installed Postgres,
we're going to run rails db:reate again.
4:43
And it's going to create a DB with
Postgres, which is a better, more, well,
4:47
not more efficient, but
better database, right?
4:51
So, rails db:reate.
4:54
And as you can see,
we have successfully created the database,
4:56
which means we have successfully
switched to PostgreSQL.
4:59
There was just one more
thing I forgot to mention.
5:02
When you run your app again and
you run rails s,
5:04
you're going to need to run
the pending migrations.
5:06
If you just hit this button, or
if you go to your terminal and
5:08
you stop the server and
then run rails db:migrate,
5:11
then this error will go away and
the migrations will be resolved.
5:14
So run pending migrations.
5:17
As you can see, it says,
could not find posts with id2.
5:18
That's because I'm looking
at a post in the URL.
5:21
So I'll just go to /posts, and
all of our posts are gone.
5:23
But that's okay,
we can just create them again.
5:26
And so, yeah,
if you run into that migration error,
5:28
just run the pending migrations and
then it'll go away.
5:30
Now, for the Mac users,
we have a tutorial here by DigitalOcean.
5:33
DigitalOcean has really good tutorials.
5:36
And it says, how to use PostgreSQL with
the Ruby on Rails application on macOS.
5:38
It's from 2019, but
it'll still work, so don't worry.
5:42
The best part about DigitalOcean is
that you can actually change and
5:45
use your specific version of macOS.
5:48
So it's gonna be more or
less the same steps.
5:49
You're gonna install Postgres.
5:51
Then here's something different, you have
to include it in your path variable so
5:53
you can access it via command line tools.
5:56
Then you have to apply the changes, and
5:58
then you have to start the service
as we did in Linux subsystem.
5:59
Then the same thing we did,
create a username, login.
6:02
This tutorial will be linked in the
description, so make sure to follow it.
6:05
Get Postgres on your machine.
6:08
You can also look at YouTube videos,
which we'll have in the description too.
6:09
I can't show you how to do it on a Mac
because I don't have one available to me,
6:12
but I can at least show
you the best tutorials so
6:15
that you can easily do it without hassle.
6:17
So check the description and
you'll find all the best tutorials.
6:19
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