DBIx::Class Update one table from another - mysql

Question

I have a SQL query which works fine directly in MySQL, but I'm struggling to convert it to use via DBIx::Class, I've simplified the query here
UPDATE table1, table2
SET table1.field1 = SOMEFUNC( table1.field4 / table2.field2 )
WHERE table1.id = table2.id
AND table1.field3 = table2.field3
AND table2.field2 IS NOT NULL
AND table2.field2 > 0;
Any suggestions?

Answer 1

In similar cases I usually perform a search on the related table. In your case you have two result sources: table1 and table2. table1 has a relationship to the table table2 (most probably) named table2. So now you perform a search in the table2 using this relationship table2.
my $resultset = $schema->resultset('table1')->search_rs(
{
me.field3 => table2.field3,
table2.field2 => {'!=', '' },
table2.field2 > 0
},
{
'join' => 'table2',
'select' => ['me.field1', 'me.field4', 'table2.field2', 'me.field4' / 'table2.field2' ],
'as' => ['field1','field4', 'field2', 'division_result']
}
);
while ( my $this_res_row = $resultset->next ) {
## Presuming somefunc is a perl subroutine
$this_res_row->update( { field1 => somefunc( $this_res_row->get_column('division_result') ) } );
}
Maybe this is the solution you have come up with, I think it is not possible to do what you want in a single dbic update() statement. Unfortunately, each update() statement will hit your database separately.
By the way, I don't think it is a good idea ta make a second union on the same tables via field3, you have it already done via id fields. Why would you need another one?
Alternatively, and I would consider it a better idea, is to use database triggers to implement your code.
Please, take into account, that I haven't tested the code and it may contain some mistakes, but you have to grasp the idea of how to get what you want.

Answer 2

What about using *_related methods?