Dolt is a SQL database with Git-style versioning. One of our biggest priorities is ensuring that Dolt is a drop in replacement for any MySQL database. That means any query that can be run on a MySQL database must run correctly on a Dolt as well.
To help measure this product objective, we adopted the sqllogictest package about a year and a half ago. It has about 6 million queries (along with the expected results) that were originally written to ensure the correctness of SQLite. 2 months later we hit 89% correctness.
Today we are proud to announce that we have hit 99% correctness on the sqllogictest package. Let's highlight a few SQL features that helped get our score up! Each of these features increased our score by about 2% (~100,000 test cases).
In February 2020, Aaron implemented SQL Views. SQL views are used to save commonly repeated queries. Dolt even versions them for you!
For example, creating a view looks like this:
CREATE VIEW getnames
SELECT first_name, last_name FROM contacts;
To use it simply do
Back in May 2020, Daylon implemented Secondary indexes. Indexes are essentially maps that allow for faster retrievals of certain keys.
Here's an example of a UNIQUE secondary index used so no duplicate emails exists.
CREATE TABLE `contacts` (
id int PRIMARY KEY,
email varchar(20) UNIQUE,
In February 2021, Zach implemented window functions. Window functions allow for more expressive computations on top of aggregations. The most popular one is ROW_NUMBER()
ROW_NUMBER() OVER w AS 'row_number',
WINDOW w AS (ORDER BY id);
Distinct Expressions for functions
Last month, I implemented DISTINCT uniqueness for functions. This syntax is useful for computations on de-duplicated data. For example, if we wanted to count all of the different first names we have, we can do
SELECT COUNT(DISTINCT *) FROM contacts
Our pursuit of 99% correctness has further validated that Dolt is a database. We will continue to ship more MySQL compliant features to hit 100% correctness along with much better performance. If you are curious about Dolt please join our discord here and learn more!