This calendar is supposed to be edited by admin users, but do not yet
have the complete JavaScript code to do so, thus for now i have made it
read-only.
I just found out that this is a feature introduced in PostgreSQL 10,
back in 2017.
Besides this being the standard way to define an “auto incremental
column” introduced in SQL:2003[0], called “identity columns”, in
PostgreSQL the new syntax has the following pros, according to [1]:
* No need to explicitly grant usage on the generated sequence.
* Can restart the sequence with only the name of the table and column;
no need to know the sequence’s name.
* An identity column has no default, and the sequence is better
“linked” to the table, therefore you can not drop the default value
but leave the sequence around, and, conversely, can not drop the
sequence if the column is still defined.
Due to this, PostgreSQL’s authors recommendation is to use identity
columns instead of serial, unless there is the need for compatibility
with PostgreSQL older than 10[2], which is not our case.
According to PostgreSQL’s documentation[3], the identity column can be
‘GENERATED BY DEFAULT’ or ‘GENERATED ALWAYS’. In the latter case, it is
not possible to give a user-specified value when inserting unless
specifying ‘OVERRIDING SYSTEM VALUE’. I think this would make harder to
write pgTAP tests, and the old behaviour of serial, which is equivalent
to ‘GENERATED BY DEFAULT’, did not bring me any trouble so far.
[0]: https://sigmodrecord.org/publications/sigmodRecord/0403/E.JimAndrew-standard.pdf
[1]: https://www.2ndquadrant.com/en/blog/postgresql-10-identity-columns/
[2]: https://wiki.postgresql.org/wiki/Don't_Do_This#Don.27t_use_serial
[3]: https://www.postgresql.org/docs/15/sql-createtable.html
I intend to use the same SVG file for customers and employees, so i had
to change Oriol’s design to add a class to layers that are supposed to
be only for customers, like trees. These are hidden in the admin area.
I understood that customers and employees have to click on a campsite to
select it, and then they can book or whatever they need to do to them.
Since customers and employees most certainly will need to have different
listeners on campsites, i decided to add the link with JavaScript. To
do so, i need a custom XML attribute with the campsite’s identifier.
Since i have seen that all campsites have a label, i changed the
“identifier” to the unique combination (company_id, label). The
company_id is there because different companies could have the same
label; i left the campsite_id primary key for foreign constraints.
In this case, as a test, i add an <a> element to the campsite with a
link to edit it; we’ll discuss with Oriol what exactly it needs to do.
However, the original design had the labels in a different layer, that
interfered with the link, as the numbers must be above the path and
the link must wrap the path in order to “inherit” its shape. I had no
other recourse than to move the labels in the same layer as the paths’.
It made no sense to have a file upload in each form that needs a media,
because to reuse an existing media users would need to upload the exact
same file again; this is very unusual and unfriendly.
A better option is to have a “centralized” media section, where people
can upload files there, and then have a picker to select from there.
Ideally, there would be an upload option in the picker, but i did not
add it yet.
I’ve split the content from the media because i want users to have the
option to update a media, for instance when they need to upload a
reduced or cropped version of the same photo, without an edit they would
need to upload the file as a new media and then update all places where
the old version was used. And i did not want to trouble people that
uploads the same photo twice: without the separate relation, doing so
would throw a constraint error.
I do not believe there is any security problem to have all companies
link their media to the same file, as they were already readable by
everyone and could upload the data from a different company to their
own; in other words, it is not worse than it was now.
This page is more or less similar to home, in terms of database: it
has a carousel and a list of items; in this case, the definition of
campsite services.
As i said early, when adding the home carousel, this carousel has its
own relation and set of functions to manage slides. They are also
duplicated in Go code, but i think i will need to refactor it later to
a carousel package or something like that, because both relations have
the exact same fields and types, so it makes no sense to have twice the
same code.
I already did it with the CSS and JavaScript code, mostly because it was
easier to replace the `.surroundings div` selector with `.carousel`, and
because that way i can have a single template that loads and initializes
Slick.
There is no UI to create or edit service definitions, although there are
the SQL functions, because i have no more time now, and Oriol needs to
check that the style is correct for that page.
I debated with myself whether to create the home_carousel relation or
rather if it would be better to have a single carousel relation for all
pages. However, i thought that it would be actually harder to maintain
a single relation because i would need an additional column to tell one
carrousel from another, and what would that column be? An enum? A
foreign key to another relation? home_carousel carries no such issues.
I was starting to duplicate logic all over the packages, such as the
way to encode media paths or “localization” (l10n) input fields.
Therefore, i refactorized them.
In the case of media path, i added a function that accepts rows of
media, because always need the same columns from the row, and it was
yet another repetition if i needed to pass them all the time. Plus,
these kind of functions can be called as `table.function`, that make
them look like columns from the table; if PostgreSQL implemented virtual
generated columns, i would have used that instead.
I am not sure whether that media_path function can be immutable. An
immutable function is “guaranteed to return the same results given the
same arguments forever”, which would be true if the inputs where the
hash and the original_filename columns, instead of the whole rows, but
i left it as static because i did not know whether PostgreSQL interprets
the “same row but with different values” as a different input. That is,
whether PostgreSQL’s concept of row is the actual tuple or the space
that has a rowid, irrespective of contents; in the latter case, the
function can not be immutable. Just to be in the safe side, i left it
stable.
The home page was starting to grow a bit too much inside the app
package, new that it has its own admin handler, and moved it all to a
separate package.
I am not happy with the localization interface for admins, but it is the
easier that i could think of (for me, i guess), with a separate for
each language.
I am not at all proud of the use of RecordArray, but i did not see the
need to create and register a type just to show the translation links.
I might change my mind when i need to add more and more translation
links, but only it the current interface remains, which i am not that
sure at the moment.
Since campsite types need a media, i have to insert also images to the
media relation. The best would be to use PostgreSQL’s
pg_read_binary_file to read the media content from actual files when
inserting the new rows, but the files need to be within the database
cluster directory, or have to use an absolute path when running as a
superuser to read from files outside the cluster directory, which means
that it would depend on the path where i leave the files, that is
different in development that in staging.
To avoid that problem i can simply insert the rows using their base64
strings, with PostgreSQL’s decode. The images are kind of small, but
i was worried that each change in demo.sql would duplicate that data in
git, even if the change is not related to the images, because git stores
the whole file; even if small, soon everything adds up.
I do not care if the _final_ demo.sql is big, as this file is packaged
in a different deb and is only installed in staging, so i’ve chosen to
use m4 to build a single “amalgamated” SQL file from the base .sql
file and the individual image files converted to base64 strings. That
way, each image is individually managed by git and the base .sql file
does not balloon up for each little change.
Changed m4’s quotes to [[ ]] because the default ` ' was interfering
with Intellij’s syntax highlighting.
jordi fita mas