Have you ever experienced going to a website that takes forever to load and wondered why? You are not alone. Even well-developed, popular web applications have performance issues. Some of these apps have pages that can take way more than 2 seconds to load, and this can easily “make or break” your website. As you might have guessed, performance is one of the top most mentioned issues in many web applications’ bug tracking systems.

Architecture of Web Applications

To understand the causes of these performance issues, we need to understand how web apps are constructed on the server side. By far the most common…


Today we are thrilled to announce our official 1.0 release of Cosette, a SQL solver for automatically checking semantic equivalences of SQL queries. With Cosette, one can easily verify the correctness of SQL rewrite rules, find errors in buggy SQL rewrites, building auto-graders for SQL assignments, developing SQL optimizers, busting “fake SQLs,” etc.

What is a SQL solver and what can it do?

As a SQL solver, Cosette checks for semantic equivalences of SQL queries. Two SQL queries are semantically equivalent if they produce the same results given any valid input relations. Here is an example of two semantically equivalent SQL queries:

These two queries will produce the exact same…

University of Washington Database Group

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