[MTOS-dev] MT::Object::load_iter() problem

[Hirotaka Ogawa]

MT::Object::load_iter() is really complicated.

When ObjectDriver is DBI::sqlite, load_iter() fetches objects from
MT::OD::D::Cache::RAM, which looks up the internal cache first and
queries the database only when lookup failed.

Otherwise, load_iter() fetches objects from MT::OD::D::DBI which
directly queries the database, and then stores fetched objects to
MT::OD::D::Cache::RAM, internal cache.  That is, when using mysql or
postgres, cached objects stored by a load_iter() are never reused by
the next load_iter() requests.  They could be reused only if they were
required by the next load() methods.

In addition, objects loaded by load_iter() seem to be leaked.  After
calling $MT::Object::DRIVER->clear_cache() which clears all contents
of the internal cache, some objects are never destroyed and still
remain in memory.

To fix this situation, load_iter() fetches objects from
MT::OD::D::Cache::RAM[1] or MT::OD::D::DBI[2], without depending on
ObjectDriver setting.

[1] Using MT::OD::D::Cache::RAM (same as DBI::sqlite case)

sub load_iter   {
    my $class = shift;
    my $driver = $class->driver;
    return scalar $driver->search($class, @_);
}

[2] Using MT::OD::D::DBI

sub load_iter   {
    my $class = shift;
    my $driver = $class->driver;
    while ( $driver->isa('Data::ObjectDriver::Driver::BaseCache') ) {
        $driver = $driver->fallback;
    }
    return scalar $driver->search($class, @_);
}

But, after applying this modification, still leak remains.

Using FCGI environment, I reapeatedly performed 'rebuild all' for a
relatively small blog with 237 entries, 390 comments, and 1745
trackbacks and measured RSS of the FCGI proccess.

Without weaken:

Initial       25,152KB
1st rebuild   60,192KB
2nd rebuild   87,144KB
3rd rebuild  114,160KB
4th rebuild  140,848KB
5th rebuild  163,164KB

With weaken:

Initial       24,544KB
1st rebuild   40,332KB
2nd rebuild   46,388KB
3rd rebuild   52,424KB
4th rebuild   58,464KB
5th rebuild   64,524KB

With weaken + load_iter mods:

Initial       24,528KB
1st rebuild   38,032KB
2nd rebuild   42,544KB
3rd rebuild   46,908KB
4th rebuild   51,204KB
5th rebuild   55,708KB

-- 
Hirotaka Ogawa makes no sense.
http://as-is.net/blog/