Blog | Querify Labs

Introduction to the Join Ordering Problem

May 2, 2021

A typical database may execute an SQL query in multiple ways, depending on the selected operators' order and algorithms. One crucial decision is the order in which the optimizer should join relations. In this blog post, we define the join ordering problem and estimate the complexity of join planning.

What is Cost-based Optimization?

Apr 19, 2021

In this blog post, we will discuss what a cost of a query plan is and how it can drive optimizer decisions.

Memoization in Cost-based Optimizers

Mar 25, 2021

Query optimization is an expensive process that needs to explore multiple alternative ways to execute the query. The query optimization problem is NP-hard, with the number of possible plans growing exponentially with the query's complexity. This blog post will discuss memoization - an important technique that allows rule-based optimizers to consider billions of alternative plans in a reasonable time.

Rule-based Query Optimization

Jan 28, 2021

In this blog post, we discuss rule-based optimization - a common pattern to explore equivalent plans used by modern optimizers. Then we analyze the rule-based optimization in Apache Calcite, Presto, and CockroachDB.

Inside Presto Optimizer

Jan 4, 2021

Presto is an open-source distributed SQL query engine for big data. In this blog post series, we explore the internals of the Presto query optimizer. In the first part, we discuss the relational tree organization, the optimizer interface, and the design of the rule-based planner.