From this answer to What database does Google use?, BigTable is not a relational database. It does not support joins nor does it support rich SQL-like queries. Is this obvious? I do not ...
What are the performance implications of polymodels versus normal BigTable models in google app engine?
What produces the best performance in regular google app engine use, a polymodel or a normal "BigTable" model? The polymodel, effectively, creates a column in the parent table called "class" which ...