All language subtitles for 005 Optimizing Data Fetching_Downloadly.ir_en

We implemented static generation

on the index JS and the eventId JS pages.

Now let's take a closer look.

It works, but maybe we can optimize it.

For example, on the starting page,

so this index JS page.

We are pre generating this page with the pre fetched data,

so to say,

but of course this data will then only update

if we build again.

So if our page was deployed for a couple of hours

or even days, and we have new featured events,

we need to redeploy our page

to reflect that latest state.

That's not ideal.

And one possible work around could be to use,

getStaticProps instead.

Then for every incoming request,

we would pre-render the page again on the fly

but this would be overkill here.

We don't need to pre generate this for every request,

just a couple of times, maybe after a certain time span.

And that's where we can add the revalidate key tutors object

which we returned side-by-side to the props key.

And we can set this to a value

of our choice to 10 seconds, 100 seconds, 10 minutes

whatever it makes sense to you.

Now, our events and the featured events

probably don't change that often.

And it's not the end of the world

if we did update them

and our starting page, doesn't immediately reflect this.

So maybe every 1,800 seconds is a good time span.

That means that every half hour we regenerate this page

for a new incoming request.

And I think that would work quite well here.

With that, this page still works,

but in production, it would be regenerated

from time to time,

at most once every half hour.

Now for eventId, we also could consider re-validating

because there it's similar.

If the details about any event changed,

we don't reflect this on our page

because we never regenerate it.

Again, we could use service side rendering for that

or we add clients site data fetching

so that we have some initial data

and we then update this with the client site data.

But we could also go for re-validating instead here,

and here I will also set revalidate to a certain interval.

Now, I will not go for half an hour here,

because for example,

if the date changes, that's more important

than the general list of featured events.

It's still okay if it's slightly outdated

but I wanna be more accurate

than on the starting page.

So, set this, let's say to 30 seconds,

so that if a new request comes in and it's more

than 30 seconds since the page was last generated,

it will be generated again.

I think that's a setting that makes sense here.

Of course, you can also go for a different duration

if that makes more sense to you though

or alternatively you solved as

with client site data fetching,

in addition to the pre rendering here.

Now, I also have an optimization idea

regarding getStaticPaths.

Currently, we're fetching all events here.

Now, in our case,

that's only free events,

but on a real page,

we could of course have hundreds or thousands of events.

So fetching all those events,

to pre generate all those pages

could be a huge waste that might really

be redundant and could lead to performance issues.

So in reality,

we might want to just pre-render our featured events

because those are more likely to be visited

because they're featured on the starting page.

So therefore here, in eventId on this eventId page,

instead of fetching all events and pre rendering

all the pages, all the detail pages for all events,

I will instead just load my featured events

and therefore import getFeaturedEvents

from the API util helper file,

and then just simply execute getFeaturedEvents down there.

But now with that, of course, that implies

that for some events, the page will not be pre-generated.

So if we leave fallback set to false, we'll have an issue.

If I click on some event, which was not, pre-generated

like this event with an idea of E1,

I get a 404 error

even though we have data for this event

but we didn't define it

in advance and therefore it wasn't pre-generated.

And since we tell next.js that we did prepare

all required pages here,

that's what we tell next.js with fallback false.

It shows as a 404 page here.

So the correct setting here,

would be true,

telling next.js that there are more pages

than the ones we prepared here.

Then it will try to dynamically generate the page

if it encounters a page which was not pre-generated before.

Now, if we do that, it works.

Now we see no event found initially

until the event was fetched

because we are checking if we don't have any event.

And then we showed us fallback and that's good.

We should show a fallback content

whilst we are waiting for the event to arrive

but here it might be better to show some

a loading spinner

or some loading text instead of an error.

Because here it's now actually expected for some events

which haven't been pre-generated

that we don't have them right from the start.

So instead of wrapping this into an error alert,

I'll wrap this in a regular div instead

and give that div a class name of center

which is a globally available class name

to find in the global CSS file.

And then I'll then say loading instead of no event found.

And therefore, now if we reload,

we see loading until the event is there

so that's better.

Alternatively, of course,

we set fallback, not too true, but to blocking.

In that case, next.js will not serve anything

until we're done generating this page.

So if I do that and reload,

then loading the page takes a bit longer

but we get the entire finished page

right from the start.

It's up to you which user experience you want on your page

or stick to this blocking approach

but you can go for either of the two.

And these were a couple of small optimized session steps

which I did want to implement.

Now with that, let's go back

to the two remaining pages we have,

maybe first to the index.js page and the events folder

and let's make sure we also pre-render those correctly

with data which is fetched in advance.

Try implementing it on your own.

We'll do it together in the next lecture.