Magento 1 Collections
Magento groupBy for collections¶
You might be running into exceptions being thrown, saying "Item (Mage_Catalog_Model_Product)" with the same id "*" already exist". And that is because multiple product records of the same item are added to collection, but that is not allowed.
Therefore you might think something like
$collection->getSelect()->groupBy('e.entity_id') will solve the problem.
Yes it will solve the problem, however if
$collection->count() is used anywhere in the project
that now becomes
1 which might break things like pagination, etc.
Better solution would be to solve it with
$collection->getSelect()->distinct(true) which would also get rid of duplicate
items, and will not break any of Magento internal counting for collections.