I'm running a complex DQL query that returns partial entities using
ResultSetMapping. Since the table has so many columns and I only need a
couple, I end up with entities that only have the needed properties
populated. The large table is an association of the entity I'm actually
fetching. I did this for performance reasons and it works very well when I
run it once. But, if I try to do this partial entity fetch more than once
during a request, then things get strange.
$benchmarks = array('unemployment_rate', 'graduation_rate');
$subs = $subscriptionModel->findWithPartialObservations($study, $year,
$benchmarks);
foreach ($subs as $sub) {
// This is only a partial observation, by design...
$observation = $sub->getObservation();
// This value will be populated
$value = $observation->get('unemployment_rate');
// If I try to get some other property, it will return null. That's ok.
$isNull = $observation->get('some_other_property');
}
// So far, so good. But if I run this again on the same request, with
different benchmarks, the problems start:
$benchmarks = array('cost_per_credit_hour', 'abc_grades');
$subs = $subscriptionModel->findWithPartialObservations($study, $year,
$benchmarks);
foreach ($subs as $sub) {
// This appears to be the same partial observation I got above, but I
don't want that.
$observation = $sub->getObservation();
// This value is missing
$value = $observation->get('cost_per_credit_hour');
// getObservation() appears to be returning the same observation as the
first time through,
// with the wrong properties populated
}
So, I need to force each findWithPartialObservations() call to go back to
the database so that when I call getObservation() on one of the results,
the correct properties are populated. After some reading, I decided that
calling clear() on the entity manager might be the answer. That tells it to
forget all entities and go back to the database when the fetch is run,
right? Well, I added the clear between the two fetches above (in other
words, right above the "So far, so good" comment. But when I run this I get
errors like:
A new entity was found through the relationship
> 'Mrss\Entity\Subscription#observation' that was not configured to cascade
> persist operations for entity: Observation id: 1693. To solve this issue:
> Either explicitly call EntityManager#persist() on this unknown entity or
> configure cascade persist this association in the mapping for example
> @ManyToOne(..,cascade={"persist"}).
>
Now, I don't want the observation to persist on cascade because the
observation is only partially populated. That would erase data by
overwriting good values with nulls for the fields that weren't populated.
I've tried passing entity names to clear() to make it more limited, but I
always get some variation on that error message. Can anyone guide me
towards a way to force my complex fetch to be drawn from the database
rather than the unit of work?
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