H2 VS Kotest

The URL should point to a particular comment, but HN removes fragments: https://github.com/h2database/h2database/issues/3686#issueco...

This sounds very much like the idiocy of "infosec" lunkheads who know nothing about what they're "fixing" but if an automated system tells them a CVE exists, they've absolutely got to have it "patched". They don't look into what the claims of the CVE are, or whether their specific use case is vulnerable. They don't know, they don't care, they're not even programmers. All they know is a box needs ticking.

A similar thing happened with h2database - a "security researcher" found that if you do something you're told not to do, then bad things happen.. but they demanded and got a CVE allocated anyway. Anyone who looks at it realises it's bullshit, but the mere existence of a CVE is all that matters to these idiots.

What the h2database developer said about it: https://github.com/h2database/h2database/issues/3686#issueco...

> I struggle to understand why I should feel the slightest shred of sympathy for "major corporations" that are using a volunteer-developed open-source project. Feel free to get your corporation to pay someone to deal with this, or pay for a similar commercial library.

> ...than it would be to learn the exact syntax and quirks and possibly bugs of someone else's implementation...

Yup. Also, having deep knowledge of the language is required.

SQLite's grammar is neat. Creating a compatible parser would make a fun project. Here's a pretty good example: https://github.com/bkiers/sqlite-parser (Actual ANTLR 4 grammar: https://github.com/bkiers/sqlite-parser/blob/master/src/main... )

Postgres, which tries to be compliant with the latest standards, however...

SQL-2016 is a beast. Not to mention all the dialects.

I'm updating my personal (soon to be FOSS) grammar from ANTLR 3 LL(k) to ANTLR 4 ALL().

I've long had a working knowledge of SQL-92, with some SQL-1999 (eg common table expressions).

But the new structures and extensions are a bit overwhelming.

Fortunately, ANTLR project has ~dozen FOSS grammars to learn from. https://github.com/antlr/grammars-v4/tree/master/sql

They mostly mechanically translate BNFs to LL(k) with some ALL(). Meaning few take advantage of left-recursion. https://github.com/antlr/antlr4/blob/master/doc/left-recursi...

Honestly, I struggled to understand these grammars. Plus, not being conversant with the SQL-2016 was a huge impediment. Just finding a succinct corbis of test cases was a huge hurdle for me.

Fortunately, the H2 Database project is a great resource. https://github.com/h2database/h2database/tree/master/h2/src/...

Now for the exciting conclusion...

My ANTLR grammar which passes all of H2's tests looks nothing like any of the official or product specific BNFs.

Further, I found discrepancy between the product specific BNFs and their implementations.

So a lot of trial & error is required for a "real world" parser. Which would explain why the professional SQL parsing tools charge money.

I still think creating a parser for SQLite is a great project.

H2 - Free, Embedded & Open source

H2 2.1

H2 for mocking relational database connections

It's open-source and written in Java, so you can even create custom procedures and register them straight in your application!

Firstly, let's set up a basic Spring Boot application. We can use the Spring Initializr with Spring Data JPA, H2 Database, Lombok added. H2 Database will provide us with a simple database, and Spring Data JPA will allow us to easily interact with it using Hibernate. Lombok will make it easier to write concise and readable classes.

Sorting chunks by similarity: commonly used tools don't do that. Most archive tools only sort by file type.

I wrote a tool that chunks the data (into variable-sized blocks, to re-sync if there are multiple files that have different length prefixes, but that's another story), and then sorts the chunks by LSH (locality sensitive hash). LSH is used by search engines to detect similar text. It can compress directories that contain multiple version of e.g. source code very well (e.g. trunk, branches). https://github.com/h2database/h2database/blob/master/h2/src/...

I discussed this approach with a researcher in this area in January 2020. AFAIK there is active research in this area, specially to compress DNA sequences. But he also wasn't aware of papers or research in this area for general-purpose data compression.

So, I think this area is largely uncharted. I would be interested (as a hobby side project) to help, if somebody is interested.

As you might know, Advent of Code will begin this Friday! If, like me, you want to have a go at solving the puzzles in Kotlin, I would like to share with you a little library I've developed to reduce boilerplate and solve the puzzles in a test-driven approach. It is based on Kotest, a modern and Kotlin-first test framework.

Kotlin testing with Kotest and MockK

As a matter of fact, in the previous examples, we have shifted a bit away from the TDD standards in the meaning that we test not only the operability of our code, but rather check if the code runs according to certain specifications (Given/When/Then). These specifications are our tests, and the syntactic sugar in the form of the possibility to give clear names to the tests using DisplayName and the grouping of the tests by a set of similar attributes helps us clearly formulate these specifications. There is an entire family of frameworks in different languages that allow us to create such specifications: for Java it is Spock, for Ruby—RSpec, and for Kotlin—Spek and Kotest frameworks. Below, I will go into more detail about them.

I've tried so many times. SO MANY. I love the idea of mutation testing. Even chatGPT couldn't help me. It just made up fake mutation testing frameworks to try. To me, pitest is dead. kotest is not mutation testing, but it's property testing is the next best thing I have found to revolutionize your unit tests.

The extensions are not particularly useful in this scenario because the described functionality can be incorporated into the Host class. On the other hand, they flourish in test frameworks like Kotest and enable the rapid development of useful add-ons like custom matchers. Extending third-party libraries with utility functions is another prevalent use case. In the next sections, we'll zero in on this specific aspect.

We're using Kotest for our unit tests and are quite happy with it.

Basic testing in Kotlin with Kotest built for kotlin specificatlly (upcoming)

Here you are: https://github.com/kotest/kotest/issues/189