An Overview of Datalog (2010)

https://clojure.github.io/clojure-contrib/doc/datalog.html

by teleforce • 2 years ago

93 23 2 years ago

clojure.github.io

29athrowaway2• 2 years ago

Datalog is tempting but can be slow.

For recursion it can be elegant, but a graph query language like Cypher is much easier to work with.

Less verbose than SQL but also much less readable.

plaguuuuuu• 2 years ago

it is totally declarative and almost like an SMT solver so has some properties that can make it more useful in certain situations - I think it might even be fully statically verifiable but not sure. would need to look it up.

I think Rust was initially using it for reference counting.

29athrowaway2• 2 years ago

No doubt that it is powerful and useful.

But it is no SQL killer or Cypher killer.

er4hn3• 2 years ago

One very fun and practical application for Datalog is Biscuits, which are a type of arbitrarily scoped authorization token: https://biscuitsec.org/.

I tried them out for a pet project over here: https://er4hn.info/blog/2024.05.08-biscuits/ and was pretty impressed with what I found. It's not a perfect solution, but I liked it a lot more than OAuth.

nine_k• 2 years ago

Speaking of which, there's a great write-to about a related kind auth token, macaroons: https://fly.io/blog/macaroons-escalated-quickly/

er4hn3• 2 years ago

Which funny enough, I learned about biscuits from a prior article Thomas wrote: https://fly.io/blog/api-tokens-a-tedious-survey/

bmacho• 2 years ago

You microservices picture is not readable, since it is dark text over transparent, over dark background.

er4hn3• 2 years ago

Thanks for the feedback. The top left corner of the page has a little sun icon that changes to a light background. I haven't gotten around to figuring out how to change pictures based on the background for good contrast.

samstave2• 2 years ago

Would love to hear the InstantDB folk input on this, as they talk about Datalog and (something else) in their design fro their query language, and stuff about GraphQL...

https://news.ycombinator.com/item?id=41322281

Under the hood we save data to postgres as triples and wrote a datalog engine for fetching data [3]. We don’t expect you to write datalog queries so we wrote a graphql-like query language that doesn’t require any build step.

stopachka2• 2 years ago

[Instant Team] We are big fans of Datalog, and Clojure's syntax for Datalog specifically.

Datalog has a simple syntax, and implementing a basic triple store is relatively straight forward. This let us build out a) a client-side store, b) an invalidation engine, and c) a multi-tenant triple store, with a team of 5.

Clojure's syntax for datalog is especially amenable too, because the language is expressed as a datastructure. We often 'build' up queries, and having the language expressed as a data structure helps us do that.

We talk about the design journey here: https://www.instantdb.com/essays/next_firebase#exploring-sql

If you're interesting in implementing one yourself, I particularly like this chapter in SICP:

https://sarabander.github.io/sicp/html/4_002e4.xhtml#g_t4_00...

samstave2• 2 years ago

Im interested in building a [many things] with Instant.

The climbing idea for example from the other thread...

But I need to formulate my use case more clearly.

I am super interested in the "iterating" you did with AJ at Subset.so -- as thats a neato thing.

My climbing idea was predicated on an idea of forking an AppID (like from your demos) whereby if I can have a class of an app that is forkable -- then others can have the same copy of my app, but they could be linked...

Actually imma reach out to you guys because I (in typing this) just formulated what I want to build with this :-)

Ill need some iterating hand-holding like subset has. :-)

HN is so amazing.

{EDIT - I just saw that the original post on datalog is from 2010! oops. I thought it was someone writing up their own thing on it...}

cricketlover• 2 years ago

Do we need another language for querying relqtional data? Why not just use SQL?

nucleogenesis• 2 years ago

Datalog is rad and has some neat ergonomics. It’s not so much a need as a want kind of thing. It’s definitely worth looking into.

I’ve only ever seen it used in Clojure(Script) projects although there’s support in other languages too.

koito17• 2 years ago

Datalog is a subset of Prolog, both of which predate SQL. By your logic, we should be asking what was the point of SQL.

DaiPlusPlus• 2 years ago

what was the point of SQL.

IBM's get-it-out-the-door release of partial (if not broken) implementation of Codd's relational-algebra model, which incorporates parts of predicate-logic, set-theory, and more besides. It kicked-off an industrywide multivendor revolution in information storage, processing, and retrieval.

...but thesedays I'm convinced the point of SQL is to have something other programming languages can point-to to deflect any criticisms of being slow or unwilling to adopt new features, being specifically unergonomic, or most of all: being entirely unresponsive to the day-to-day needs of present-day application developers.

packetlost• 2 years ago

Datalog is strictly more powerful than SQL and way easier to understand recursive, self-referential queries than CTEs.

burakemir• 2 years ago

I am sure Clojure is great but it really shows the need for an "overview of datalog" that is not embedded in the context of a programming language with it's own syntactic choices.

My own humble attempt is here https://github.com/google/mangle ... I had come across datalog in Clojure and thought it is a complete nonstarter. Most people (including me) are not in a position to start using Clojure if all they want is a query capability.

IMHO what most people would want a datalog implementation that is very easy to integrate into their existing setup, with their existing data. Yet for extensibility it is also important to enable users to write datalog queries in it's own special syntax so one can have type checking, modules, declarations in a way that is independent of the host programming language.

From a teaching point of view, one does need an example database. Here is "employee department boss", with a volunteering spin: https://github.com/google/mangle/blob/main/docs/example_volu...

There is a long history of approaches to integrate querying into programming languages (eg LINQ). Trade off here between making an easy to use yet powerful query language, keeping it simple and integrating it tightly into the host language or using a DSL along clear interface.

truckerbill• 2 years ago

Check out cozo

aarroyoc• 2 years ago

A good video about Datalog: https://www.youtube.com/watch?v=M5fwAkJqAVw

pgt• 2 years ago

Learn Datalog Today: https://www.learndatalogtoday.org/

stuartrexking• 2 years ago

Clojure is the girl you should have married but didn’t.

An Overview of Datalog (2010)

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