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Logica – Declarative logic programming language for data

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Re: Logica – Declarative logic programming language for data

#51

Post by foobarqux »

kukkeliskuu wrote: post #35
foobarqux wrote: post #21

There don't seem to be any examples of how to connect to an existing (say sqlite) database even though it says you should try logica if "you already have data in BigQuery, PostgreSQL or SQLite,". How do you connect to an existing sqlite database?

I was turned off by this at first, but then tried it out. These are mistakes in the documentation. The tools just work with PostgreSQL and SQLite without any extra work.

How do you connect to an existing database so that you can query it? There are examples of how you can specify an "engine" which will create a new database and use it as a backend for executing queries but I want to query existing data in an sqlite database.

Re: Logica – Declarative logic programming language for data

#52

Post by diggan »

thenaturalist wrote: post #46
usgroup wrote: post #44

Earlier quoted context omitted.

I may be misremembering but I think that at the time, Logica was the work of one developer who happened to be at Google. I'm not sure that there was an institutional push to use this language, nor that it has significant adoption at Google itself.

This seems supported by the fact that the repo is not under a Google org and it has a single maintainer.

> that the repo is not under a Google org

I don't think that matters? github.com/google has a bunch of projects with large warnings that "This is not a Google project", not sure why or how that is. From the outside it looks like if you work at Google, they take ownership of anything you write.

Re: Logica – Declarative logic programming language for data

#53

Post by pstoll »

anorak27 wrote: post #33

There's also Malloy[0] from Google that compiles into SQL > Malloy is an experimental language for describing data relationships and transformations. [0]: https://github.com/malloydata/malloy

Came here to mention Malloy. Which is from the team that built Looker, which Google acquired. The Looker CTO founder then started (joined?) Malloy. And … he recently 6mo ago moved from Google to Meta.

https://www.linkedin.com/posts/medriscoll_big-news-in-the-da...

Also for those playing along at home - a few other related tools for “doing more with queries”.

- AtScale - a semantic layer not dissimilar to LookML but with a good engine to optimize pre building the aggregates and routing queries among sql engines for perf.

- SDF - a team that left Meta to make a commercial offering for a sql parser and related tools. Say to help make dbt better.

(No affiliation other than having used / been involved with / know some of these people at work)

Re: Logica – Declarative logic programming language for data

#54

Post by azornathogron »

diggan wrote: post #52
thenaturalist wrote: post #46

Earlier quoted context omitted.

This seems supported by the fact that the repo is not under a Google org and it has a single maintainer.

> that the repo is not under a Google org I don't think that matters? github.com/google has a bunch of projects with large warnings that "This is not a Google project", not sure why or how that is. From the outside it looks like if you work at Google, they take ownership of anything you write.

> From the outside it looks like if you work at Google, they take ownership of anything you write.

That is precisely how it works.

Disclaimer: I am not a lawyer, and I'm sure the validity and enforceability of the relevant contract clauses varies by jurisdiction.

Re: Logica – Declarative logic programming language for data

#55

Post by pstoll »

thom wrote: post #49
thenaturalist wrote: post #45

Earlier quoted context omitted.

Never heard of M4 before and, lo and behold, of course HN has a discussion of it: https://news.ycombinator.com/item?id=34159699 The author discusses Logica vs. plain SQL vs POSIX. I’d always start with dbt/ Sqlmesh. The library you’re talking about exists: dbt packages. Check out hub.getdbt.com and you’ll find dozens of public packages for standardizing sources, data formatting or all kinds of data ops. You can use a…

M4 is absolutely ancient, one of those things you've probably only seen flashing by on your screen if you've found yourself running `make; make install`. I suppose it is a perfectly cromulent tool for SQL templating but you're right that you must be able to get more mileage out of something targeted like dbt/SQLMesh.

Having debugged my share of autoconf setups..I assumed it had to be a new M4 and not the ancient quirky GNU M4 thing because no one in their right mind would wish M4 (and related GNU autoconfig / autconf) on any other sentient beings.

It’d be like saying - “hey, I’m starting a new project and trying to pick between ed, sed, or awk. Whatcha think”? Def not.

Re: Logica – Declarative logic programming language for data

#56

Post by pstoll »

thom wrote: post #49
thenaturalist wrote: post #45

Earlier quoted context omitted.

Never heard of M4 before and, lo and behold, of course HN has a discussion of it: https://news.ycombinator.com/item?id=34159699 The author discusses Logica vs. plain SQL vs POSIX. I’d always start with dbt/ Sqlmesh. The library you’re talking about exists: dbt packages. Check out hub.getdbt.com and you’ll find dozens of public packages for standardizing sources, data formatting or all kinds of data ops. You can use a…

M4 is absolutely ancient, one of those things you've probably only seen flashing by on your screen if you've found yourself running `make; make install`. I suppose it is a perfectly cromulent tool for SQL templating but you're right that you must be able to get more mileage out of something targeted like dbt/SQLMesh.

Also +1 for cromulent use of “cromulent”.

Re: Logica – Declarative logic programming language for data

#57

Post by aseipp »

cess11 wrote: post #40
aseipp wrote: post #20

Earlier quoted context omitted.

For the record, I don't use Logica myself so I'm not familiar with every design decision or feature -- I'm not a Python programmer. I'm speaking about Datalog in general. > making variables implicit at the call site What example are you looking at? The NewsData example for instance seems pretty understandable to me. It seems like for any given predicate you can either take the implicit name of the column or you can m…

They define a NewsData/5, but use a NewsData/2. Are you aware of any SQL transpilers that spend so much time transpiling that you get irritated? I'm not.

Ah, I see what you mean. I'm not sure predicates like NewsData can actually be overloaded by arity, I'd have to check the docs. It mostly just seems like a shorter way to write the predicate with unbound variables.

> Are you aware of any SQL transpilers that spend so much time transpiling that you get irritated? I'm not.

Again, when you are running a tool on something that returns results in ~millisecond time, it is important the tool does not spoil that. Even 100-200ms is noticeable when you're typing things out. They could have worded it differently, it's probably just typical "A programmer wrote these docs" stuff, so it's just bad copy. A dedicated technical writer would probably do something different.

Re: Logica – Declarative logic programming language for data

#58

Post by avodonosov »

puzzledobserver wrote: post #42
avodonosov wrote: post #26

> Composite(a * b) distinct :- ... Wait, does Logica factorize the number passed to this predicate when unifying the number with a * b? So when we call Composite (100) it automatically tries all a's and b's who give 100 when m7ltiplied I'd be curious to see the SQL it transpiles to.

As someone who is intimately familiar with Datalog, but have not read much about Logica: The way I read these rules is not from left-to-right but from right-to-left. In this case, it would say: Pick two numbers a > 1 and b > 1, their product a*b is a composite number. The solver starts with the facts that are immediately evident, and repeatedly apply these rules until no more conclusions are left to be drawn. "But th…

Bottom-up? Ok, I see. From the tutorial it seems Logica reifies every predicate into an actual table (except for what they call "infinite predicates")

I found a way to look at the SQL it generates without installing anything:

Execute the first two cells in the online tutorial collab (the Install and Import). Then replace the 3rd cell content with the following and execute it:

    %%logica Composite

    @Engine("sqlite"); # don't try to authorise and use BigQuery

    # Define numbers 1 to 30.
    Number(x + 1) :- x in Range(30);
  
    # Defining composite numbers.
    Composite(a * b) distinct :- Number(a), Number(b), a > 1, b > 1;
  
    # Defining primes as "not composite".
    Prime(n) distinct :- Number(n), n > 1, ~Composite(n);
Look at the SQL tab in the results.

Re: Logica – Declarative logic programming language for data

#59

Post by avodonosov »

puzzledobserver wrote: post #42
avodonosov wrote: post #26

> Composite(a * b) distinct :- ... Wait, does Logica factorize the number passed to this predicate when unifying the number with a * b? So when we call Composite (100) it automatically tries all a's and b's who give 100 when m7ltiplied I'd be curious to see the SQL it transpiles to.

As someone who is intimately familiar with Datalog, but have not read much about Logica: The way I read these rules is not from left-to-right but from right-to-left. In this case, it would say: Pick two numbers a > 1 and b > 1, their product a*b is a composite number. The solver starts with the facts that are immediately evident, and repeatedly apply these rules until no more conclusions are left to be drawn. "But th…

Where does your intimate knowledge of Datalog comes from? Do you use Datalog regularly (maybe with Datomic)? Or you just studied how it is implemenced out of curiosity?

Re: Logica – Declarative logic programming language for data

#60

Post by evgskv »

foobarqux wrote: post #21

There don't seem to be any examples of how to connect to an existing (say sqlite) database even though it says you should try logica if "you already have data in BigQuery, PostgreSQL or SQLite,". How do you connect to an existing sqlite database?

Yeah, we need better tutorials.

To use SQLite use @Engine("sqlite") imperative. And you can then connect to you database file with @AttachDatabase imperative.

For example if you have example.db file with Fruit table which has col0 column, then you can count fruits with program:

@Engine("sqlite"); @AttachDatabase("example", "example.db");

CountFruit(fruit) += 1 :- Fruit(fruit);

Then run CountFruit predicate.

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