102. stop that join! discarding dimension tables when learning high capacity classifiers
Department: Computer Science & Engineering
Faculty Advisor(s): Vraj Shah
Name: Vraj Paragbhai Shah
Grad Year: 2018
Many datasets have multiple tables connected by key-foreign key dependencies. Data scientists usually join all tables to bring in extra features from the so-called dimension tables. Unlike the statistical relational learning setting, such joins do not cause record duplications, which means regular IID models are typically used. Recent work demonstrated the possibility of using foreign key features as representatives for the dimension tables' features and eliminating the latter a priori, potentially saving runtime and effort of data scientists. However, the prior work was restricted to linear models and it established a dichotomy of when dimension tables are safe to discard due to extra overfitting caused by the use of foreign key features. In this work, we revisit that question for two popular high capacity models: decision tree and SVM with RBF kernel. Our extensive empirical and simulation-based analyses show that these two classifiers are surprisingly and counter-intuitively more robust to discarding dimension tables and face much less extra overfitting than linear models. We provide intuitive explanations for their behavior and identify new open questions for further ML theoretical research. We also identify and resolve two key practical bottlenecks in using foreign key features.
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