Perl Catalyst DBIx Cursor Cache - how to clear? - perl

Question

apologises and thanks in advance for what, even as I type, seems likely silly question, but here goes anyway.
I have basic Catalyst application using DBIx::Class with an 'Author' and associated 'Book' table. In addition I also use DBIx::Class::Cursor::Cached to cache data as appropriate.
The issue is that, following an edit, I need to clear cached data BEFORE it has actually expired.
1.) Author->show_author_and_books which fetchs and caches resultset.
2.) the Book->edit_do which needs to clear the cached data from the Author->show_author_and_books request.
See basic/appropriate setup below.
-- MyApp.pm definition including backend 'Cache::FileCache' cache.
__PACKAGE__->config(
name => 'MyApp',
...
'Plugin::Cache' => { 'backend' => { class => 'Cache::FileCache',
cache_root => "./cache",
namespace => "dbix",
default_expires_in => '8 hours',
auto_remove_stale => 1
}
},
...
-- MyApp::Model::DB definition with 'Caching' traits set using 'DBIx::Class::Cursor::Cached'.
...
__PACKAGE__->config(
schema_class => 'MyApp::Schema',
traits => [ 'Caching' ],
connect_info => { dsn => '<dsn>',
user => '<user>',
password => '<password>',
cursor_class => 'DBIx::Class::Cursor::Cached'
}
);
...
-- MyApp::Controller::Author.pm definition with 'show_author_and_books' method - resultset is cached.
...
sub show_author_and_books :Chained('base') :PathPart('') :Args(0)
{
my ( $self, $c ) = #_;
my $author_id = $c->request->params->{author_id};
my $author_and_books_rs = $c->stash->{'DB::Author'}->search({ author_id => $author_id },
{ prefetch => 'book' },
cache_for => 600 } ); # Cache results for 10 minutes.
# More interesting stuff, but no point calling $author_and_books_rs->clear_cache here, it would make no sense:s
...
}
...
-- MyApp::Controller::Book.pm definition with 'edit_do' method which updates book entry and so invalidates the cached data in show_author_and_books.
...
sub edit_do :Chained('base') :PathPart('') :Args(0)
{
my ( $self, $c ) = #_;
# Assume stash contains a book for some author, and that we want to update the description.
my $book = $c->stash->{'book'}->update({ desc => $c->request->params->{desc} });
# How do I now clear the cached DB::Author data to ensure the new desc is displayed on next request to 'Author->show_author_and_books'?
# HOW DO I CLEAR CACHED DB::Author DATA?
...
}
Naturally I'm aware that $author_and_books_rs, as defined in Author->show_author_and_books, contains a method 'clear_cache', but obviously this is out of scope in Book->edit_do ( not to mention another problem there might be).
So, is the correct approach to make the DBIx request again , as per ...show_author_and_books and then call the 'clear_cache' again that or is there a more direct way where I can just say something like this $c->cache->('DB::Author')->clear_cache?
Thank you again.
PS. I'm sure when I look at this tomorrow, the full silliness of the question will hit me:s

Answer 1

Try
$c->model( 'DB::Author' )->clear_cache() ;

Answer 2

The solution I went for in the end was to NOT use 'DBIx::Class::Cursor::Cached', but instead directly use the Catalyst Cache plugin defining multiple
backend caches to handle the different namespaces I trying to manage in the real-world scenario.
I backed away from D::C::Cursor::Cached as all data was/is held in the same namespace plus there doesn't appear to be a method to expire data in advance of
time already set.
So for completeness, from the code above, the MyApp::Model::DB.pm definition would lose the 'traits' and 'cursor_class' key/values.
Then...
The MyApp.pm Plugin::Cache' would expand to contain multiple cache namespaces...
-- MyApp.pm definition including backend 'Cache::FileCache' cache.
...
'Plugin::Cache' => { 'backends' => { Authors => { class => 'Cache::FileCache',
cache_root => "./cache",
namespace => "Authors",
default_expires_in => '8 hours',
auto_remove_stale => 1
},
CDs => { class => 'Cache::FileCache',
cache_root => "./cache",
namespace => "CDs",
default_expires_in => '8 hours',
auto_remove_stale => 1
},
...
}
...
-- MyApp::Controller::Author.pm definition with 'show_author_and_books' method - resultset is cached.
...
sub show_author_and_books :Chained('base') :PathPart('') :Args(0)
{
my ( $self, $c ) = #_;
my $author_id = $c->request->params->{author_id};
my $author = $c->get_cache_backend('Authors')->get( $author_id );
if( !defined($author) )
{
$author = $c->stash->{'DB::Author'}->search({ author_id => $author_id },
{ prefetch => 'book', rows => 1 } )->single;
$c->get_cache_backend('Authors')->set( $author_id, $author, "10 minutes" );
}
# More interesting stuff, ...
...
}
...
-- MyApp::Controller::Book.pm definition with 'edit_do' method which updates book entry and so invalidates the cached data in show_author_and_books.
...
sub edit_do :Chained('base') :PathPart('') :Args(0)
{
my ( $self, $c ) = #_;
# Assume stash contains a book for some author, and that we want to update the description.
my $book = $c->stash->{'book'}->update({ desc => $c->request->params->{desc} });
# How do I now clear the cached DB::Author data to ensure the new desc is displayed on next request to 'Author->show_author_and_books'?
# HOW DO I CLEAR CACHED DB::Author DATA? THIS IS HOW, EITHER...
$c->get_cache_backend('Authors')->set( $c->stash->{'book'}->author_id, {}, "now" ); # Expire now.
# ... OR ... THE WHOLE Authors namespace...
$c->get_cache_backend('Authors')->clear;
...
}
NOTE : as you'll expect from the use of Author and CDs, this isn't the real world scenario I'm working, but should serve to show my intent.
As I'm relatively new to the wonder of DBIx and indeed Catalyst, I'd be interested to hear if there a better approach to this (I very much expect there is), but it will serve for the moment as I'm attempting to update a legacy application.

Answer 3

The plugin could probably be patched to make per result set caches easy to namespace and clear independently, and alternatively it would probably not be so hard to add a namespace to the attributes. If you want to work on that hit #dbix-class and I'd be willing to mentor you - jnap