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There are two things wrong here.
Firstly, you’ve misunderstood what select_related() does. It doesn’t bring the fields from the related model into the current one. Instead, it just pre-fetches the related instance, so that doing the model_instance.foreignkey_field.field_on_related_model doesn’t cause another db hit.
Secondly, your models contradict what you originally said about the foreignkey. You said it was from GeoLocation to Records, but the model definitions show that is the other way round. select_related does not work in that direction – there is no way, given your current models, to query GeoLocation and get the related Records in one go. However, you can query Records and get the related GeoLocations.
(Thirdly, your answer to my comment about the use of the single-element in lookup is completely irrelevant. Use tags_slug=tag.)