Provided by: libdbix-class-helpers-perl_2.036000-2_all 
NAME
DBIx::Class::Helper::ResultSet::DateMethods1::Announce - Original Announcement of
DBIx::Class::Helper::ResultSet::DateMethods1
Content
A little over three years ago <https://github.com/frioux/dbic-
withdates/commit/5e6893d4cb873eca75118061c104bed9b891dee0> I got inspired while on vacation to Crested
Butte, CO and started a branch in DBIC called merely, "date-ops." The idea was to allow users to call
various date functions, portably, directly in DBIC. With some help from some people who use other
databases, I got it working with SQL Server, SQLite, PostgreSQL, MySQL, and Oracle.
Unfortunately after we finished it ( about six months after I started <https://github.com/frioux/dbic-
withdates/commit/fcb5b33a58426ee9d4b87fd84144d05d7a1cf9e9> ) it merely languished. There were some
technical issues we never got around to ironing out, mostly because it wasn't clear to us what the cost
of not taking care of them would be.
Fast forward a few more months and I was working on a greenfield project at work. I wanted to do some
date math in the database, so far I did all of my development against SQLite but deployed to SQL Server,
and it looked like the date ops were my solution. I decided that given that I was the primary author of
them, I could live with deploying them to production. I did exactly that and had pretty much no
problems. Well, no problems until I had to upgrade DBIC. Every time I needed to upgrade DBIC I had to
merge/rebase the branch. It turned out to be much more work than I bargained for, and I ended up just
never updating DBIC.
At some point ( just under a month ago <https://github.com/frioux/DBIx-Class-
Helpers/commit/5fefda2e5dafb0b78e9ee5a687fb698899d8d2ff> ) I decided that I needed to upgrade DBIC and
that maintaining these date ops was no longer tenable. Armed with three more years of experience than I
had when I started I embarked on converting the date ops to date methods, that would work as Helpers. In
addition to not being core, so I could release at my own pace, I could also version the API, so if I end
up making some critical mistakes or needing to break the API for some features in the future, I can
merely release "::DateMethods2". So without further ado:
Announcing "DBIx::Class::Helper::ResultSet::DateMethods1"
Do you store dates in your database? Do you ever want to manipulate them efficiently? Well here's your
solution!
First, how do you search in a more comprehensible way?
$rs->dt_on_or_before(
{ -ident => '.when_created' },
DateTime->now->subtract(days => 7),
);
"dt_on_or_before" (as well as "dt_before", "dt_on_or_after", or "dt_after") merely aliases "<=", "<",
">=", and ">", respectively. Instead of trying to think about the numerical meaning of a date on a
timeline, just use these named methods. In addition to the nicer name, they can take DateTime object
(which are automatically converted to UTC), and autoprepend "current_source_alias" in
DBIx::Class::ResultSet when passed an "-ident" that starts with a ".". You can pass any of a value, a
column (via "-ident"), a subquery, literal sql, or a "DateTime" object to either parameter slots of these
methods.
Second, how do I really leverage this module to do stuff with dates in my database?
Here's a query I originally wrote with date ops. Basically it groups some columns by some "date parts"
like year, month, day, etc. You can use it to make nice reports of things like how many things have been
done per month, or maybe find out if the system is more busy in the summer:
$rs->search(undef, {
columns => {
count => '*',
year => $rs->dt_SQL_pluck({ -ident => '.start' }, 'year'),
month => $rs->dt_SQL_pluck({ -ident => '.start' }, 'month'),
},
group_by => [
$rs->dt_SQL_pluck({ -ident => '.start' }, 'year'),
$rs->dt_SQL_pluck({ -ident => '.start' }, 'month'),
],
)->hri->all
I use that exact query (though I give the user a UI for which dateparts to include) in my system, and it
works on SQL Server and SQLite, and it's fast. Awesome.
Or how about a query to discover how many issues were resolved before the next full day after their
creation? Check it out:
# note that 'day', 1 should also work
$rs->dt_before(
{ -ident => '.resolution' },
$rs->dt_SQL_add({ -ident => '.creation' }, 'hour', 24),
)->all
Both of the above queries work on all of the supported datebases!
Third, some little helpers to extend the above.
On top of those things, I also throw in a couple other handy methods. One, "utc" converts a DateTime
object to a string, in the UTC timezone. Hopefully you shouldn't need it directly, but I've already
ended up using it in places where our code forced me to return a simple hash to get merged into a search
query, instead of letting me call methods on an RS.
Another lagniappe is "utc_now" which returns some literal sql that resolves to the current date and time
in UTC on your database. You can pass it in to search just like you would datetime. So if your server
and your database have in sync clocks, these would do the same thing:
$rs->dt_on_or_before(
{ -ident => '.when_created' },
DateTime->now->subtract(days => 7),
);
$rs->dt_on_or_before(
{ -ident => '.when_created' },
$rs->dt_SQL_add($rs->utc->now, 'day', -7),
);
(NOTE: many people seem to hold suspect the idea that the clock is correct on a given server. If you
can't trust the clock of a server, you probably can't trust the server. Use NTP.)
And that's it. I hope you can use and enjoy these helpers!
SEE ALSO
original blog post <https://blog.afoolishmanifesto.com/posts/announcing-helper-resultset-datemethods1/>
AUTHOR
Arthur Axel "fREW" Schmidt <frioux+cpan@gmail.com>
COPYRIGHT AND LICENSE
This software is copyright (c) 2020 by Arthur Axel "fREW" Schmidt.
This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5
programming language system itself.
perl v5.36.0 DBIx::Class::Helper::ResultSet::DateMethods1::Announcement(3pm)