Extracting date parts using DBIC while keeping queries database agnostic - perl

Question

I use a MySQL database in production and a SQLite database for running tests. One part of my application is used to gather monthly statistics for a year. I've successfully done this, however it came at a cost of not being able to automate tests because I'm using MySQL specific functions when querying for the data:
my $criteria = {
status => ['Complete'],
'YEAR(completed_on)' => DateTime->now()->year(),
};
my $attributes = {
select => [ { count => 'title' }, 'completed_on' ],
as => [qw/num_completed datetime/],
group_by => [qw/MONTH(completed_on)/],
};
Notice I'm using YEAR and MONTH MySQL functions.
I know one way I can substitute the where clause to eliminate the use of MySQLs YEAR function, something like this:
my $dtf = $schema->storage->datetime_parser;
my $begin_date = DateTime->from_day_of_year( year => DateTime->now()->year(), day_of_year => 1 ); #inception o_O
my $end_date = DateTime->from_day_of_year( year => DateTime->now()->year(), day_of_year => 36[56] );
my $criteria = {
status => ['Complete'],
completed_on =>
-between => [
$dtf->format_datetime($begin_date),
$dtf->format_datetime($end_date),
]
};
Using the recommended way to query date fields using DBIC
But I'm stumped as to what to do with the group_by clause and how to make the grouping of this fields date value by month database agnostic as well. Wondering if anyone has any ideas?
Thanks!

Answer 1

Sometimes you will have to make engine specific code in DBIx::Class if you're trying to do special things. You can use $schema->storage->sqlt_type to make different SQL.
Note you can also use substr(completed_on,1,4) to get the year in SQLite.
This will solve your problem:
my $type = $schema->storage->sqlt_type;
my $criteria;
my $attributes;
if ($type eq 'MySQL') {
$criteria = {
status => ['Complete'],
'YEAR(completed_on)' => DateTime->now()->year(),
};
$attributes = {
select => [ { count => 'title' }, 'completed_on' ],
as => [qw/num_completed datetime/],
group_by => [qw/MONTH(completed_on)/],
};
}
elsif ($type eq 'SQLite') {
my $dtf = $schema->storage->datetime_parser;
my $begin_date = DateTime->from_day_of_year( year => DateTime->now()->year(), day_of_year => 1 ); #inception o_O
my $end_date = DateTime->from_day_of_year( year => DateTime->now()->year() + 1, day_of_year => 1 )->add( seconds => -1 );
$criteria = {
status => ['Complete'],
completed_on => {
-between => [
$dtf->format_datetime($begin_date),
$dtf->format_datetime($end_date),
]
}
};
$attributes = {
select => [ { count => 'title' }, 'completed_on' ],
as => [qw/num_completed datetime/],
group_by => ['substr(completed_on,6,2)'],
};
}