Clojurians Log v2

Hi, I'm trying to do a select in database using Honey sql in clojure. My database is MYSQL, and this is the sql that i want: select LPAD(CardPayment.authorization_code, 6, 0) as authorization from CardPayment

Someone know how to use LPAD function in honeysql? I dont find in the documents and examples

@contato509

user=> (require '[honeysql.core :as h] '[honeysql.helpers :refer [select from]])
nil
user=> (-> (select #sql/call [:lpad :CardPayment.authorization_code 6 0]) (from :CardPayment) (h/format))
["SELECT lpad(CardPayment.authorization_code, ?, ?) FROM CardPayment" 6 0]

@seancorfield thanks so much, you save my day of work

With the AS alias:

user=> (-> (select [#sql/call [:lpad :CardPayment.authorization_code 6 0] :authorization]) (from :CardPayment) (h/format))
["SELECT lpad(CardPayment.authorization_code, ?, ?) AS authorization FROM CardPayment" 6 0]
user=> 

And here's an alternative if you need parameters to lpad being evaluated (so it uses h/call instead of the tagged literal):

user=> (-> (select [(h/call :lpad :CardPayment.authorization_code 6 0) :authorization]) (from :CardPayment) (h/format))
["SELECT lpad(CardPayment.authorization_code, ?, ?) AS authorization FROM CardPayment" 6 0]
user=> 

It worked, thanks

Has anyone looked into wrapping the "R2DBC" libraries from the creators of Spring, a way to communicate with your database in a "non-blocking" fashion? It's bascially based on a java library called "Reactor" and compatible with rx java.

From a performance perspective, I guess it's interesting. But I found the interop quite cubersome when trying to wrap it with clojure.

https://r2dbc.io/

I've seen a couple of people over the years ask about async database I/O libraries but they're always non-standard and niche. Sometimes they're just "fake" async wrappers around JDBC (which is inherently blocking/sync), sometimes they're proprietary to a specific database. A couple of initiatives in that area have posted notices that they are no longer maintained. I think once we have fibers (lightweight threads from Project Loom) in the JDK and good adoption, we'll start to see some interesting stuff within and around JDBC.

That r2dbc API looks very builder-centric which is not a nice pattern to work with from Clojure really, although clojure.java.data.builder would probably make it more palatable @jarvinenemil

https://github.com/clojure/java.data#usage-with-builder-classes

there is a presentation where oracle says they will no longer work on ADBA (which was some kind async database access standard) and that project loom is the future

https://www.oracle.com/mx/a/tech/docs/dev6323-reactivestreams-fiber.pdf

nicer would be a clojure data access library that talks directly to postgres, no jdbc, no idea how much work it would be but pg is well documented

looks like there is a java one already https://vertx.io/docs/vertx-pg-client/java/

Thank you! That was one of the ones I was thinking of, yes!

@kaxaw75836 Except all those of us who do not use PostgreSQL 🙂

@seancorfield do you pick mysql for new projects?

We use Percona's fork of MySQL for all our projects at work.

Years ago we were a SQL Server shop (back when we ran Windows servers in production). But we switched from IIS/Windows/SQL Server to Apache/Red Hat/MySQL about ten years ago and we've been very happy with that.