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Lutra: General-Purpose Query Language (lutra-lang.org)
submitted 10 months ago by to c/programming@programming.dev
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For the last year, I've been working on a query language that aims to replace SQL and data frame libraries. It's continuation of my work on PRQL and EdgeQL.

Now I need feedback on usability, ergonomics and overall design. Read trough the examples, check out the CLI & tell me what could be better.

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[–] 2 points 10 months ago (1 child) 
func get_album_by_id(album_id: int16): Album -> (
  get_albums()
  | find(func (this) -> this.id == album_id)
)

I'll admit I'm not a database guy, but isn't this inefficient? It looks like it's first querying the DB for all albums, then filtering the results in the interpreter. I assume the db engine has a more optimal implementation for when you do SELECT WHERE query, designed for whatever data structures it's using internally.

Also, minor nitpick but why does it have so many different ways to define a function body?

func something() -> { ... }
func something() -> ( ... )
func something() -> ...
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  • [–] [S] 2 points 10 months ago

    Two great questions!

    First one comes down to how database query optimization and predicate pushdown in particular. In this case, albums would probably have an index on albums.id column, which would optimize get_album_by_id into a single index lookup. Ideally, I would want to have an explicit function for this, something like sql::from_index("albums", "id", 3), but there is no such thing as explicit index lookup in PostgreSQL right now.

    Regarding different function syntaxes:

    • curly braces { ... } construct a new tuple (think object, struct, record),
    • parenthesis are used for precedence. They are not strictly needed for function bodies, but they do give a better visual guide to multi-line definitions, especially when using pipe operator.

    So:

    func something() -> { ... }  # constructs a new tuple
func something() -> ( ... )  # returns a value
func something() -> ...      # equivalent to ( ... )
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