Hacker News Reader

Comment by bokwoon | Hacker News Reader

> at the same time, they provide little (or nothing) utilities to map the data coming from a complex query, back to objects

Example of a query builder with built-in mapping capabilities (it’s mine):

https://github.com/bokwoon95/sq

I feel some exasperation when I see query builders that throw a query string back to the user and ask them to map the results themselves. That’s easily the most tedious and mistake-prone part of using SQL queries. In the case of my library, projection and mapping are handled by the same callback function so in order to SELECT a field you basically map it and it’s automatically added to the SELECT clause.

View on HN

I skim-read it but couldn't find an example of what I think as challenging: a join of 3 tables (well, even two).

When you join 3 tables (assuming has many and "has many through" relationships), what you get back is enormous rows and multiple rows, all of this in tabular form, but in the software is usually represented as a graph. I'd love a library that helps building back these massive rows into relationships.

Please forgive me if your library does this, while I saw the "mapping function", I didn't see anything to help me build back graphs. I can map rows "easily", but I cannot recreate associations easily, it requires a bunch of work.

> I didn't see anything to help me build back graphs

Hmm you've certainly given me something to think about. Thanks.

BTW joins are not challenging, but you made me realize I didn't show any joins in my basic examples. Here is an UPDATE with JOIN in the meantime: https://bokwoon.neocities.org/sq.html#postgres-update-with-j....

Thank you for the examples. I see the joins example, but they seem to be about creating queries, not mapping data.

    sql = "select blog.name, post.content, author.display_name from blog join post on blog.id = post.blog_id join author on post.author_id = author.id"

Assuming the relationship: many blogs have many posts and posts have one author, I'd expect something along the lines of (sudo code):

    schemaOnTheFly = Blogs{}.HasMany(Posts{}.HasOne(Author{}) // Sorry the syntax for this doesn't really exist
    blogs := query.Exec(sql, params, schemaOnTheFly)

    fmt.Printf("%+v\n", blogs[0].Posts[0].Author)

That's what I'd expect. Do notice that the schema is per-query, I'll let the developer handle the sharing portion of the schema (might be shared by a few queries)

Reply on news.ycombinator.com