Coexecutability for Efficient Verification of Data Model Updates Ivan Bocic´∗, Tevfik Bultany Department of Computer Science University of California, Santa Barbara, USA ∗
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[email protected] Abstract—Modern applications use back-end data stores for 1 class PostsController persistent data. Automated verification of the code that updates 2 def destroy_tags the data store would prevent bugs that can cause loss or 3 ... 4 posts = Post.where(id: params[:post_ids]) corruption of data. In this paper, we focus on the most challenging 5 ... part of this problem: automated verification of code that updates 6 posts.each do |p| the data store and contains loops. Due to dependencies between 7 p.tags.destroy_all! loop iterations, verification of code that contains loops is a hard 8 end problem, and typically requires manual assistance in the form of 9 ... loop invariants. We present a fully automated technique that 10 end 11 end improves verifiability of loops. We first define coexecution, a method for modeling loop iterations that simplifies automated Fig. 1. An Example Action reasoning about loops. Then, we present a fully automated static program analysis that detects whether the behavior of In our earlier work [5], we demonstrated that one can a given loop can be modeled using coexecution. We provide check invariants about the data store by translating verification a customized verification technique for coexecutable loops that queries about actions to satisfiability queries in First Order results in more effective verification. In our experiments we Logic (FOL), and then using an automated FOL theorem observed that, in 45% of cases, modeling loops using coexecution reduces verification time between 1 and 4 orders of magnitude.