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) 2014 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.