From: Logan Capaldo <logancapaldo@...>
Date: 2006-12-06T09:31:44+09:00
Subject: Re: Lisp comprehensions => SQL

On Wed, Dec 06, 2006 at 07:27:31AM +0900, Victor Zverok Shepelev wrote:
> From: Logan Capaldo [mailto:logancapaldo@gmail.com]
> Sent: Wednesday, December 06, 2006 12:15 AM
> >To: ruby-talk ML
> >Subject: Re: Lisp comprehensions => SQL
> >
> >On Wed, Dec 06, 2006 at 06:58:49AM +0900, Victor Zverok Shepelev wrote:
> >> Hi all.
> >>
> >> Random idea, just for fun - using "list comprehensions" for SQL queries
> >> generation.
> >>
> >> employees = Table.new(:id, :name, :sec_name, :salary, :age)
> >>
> >> employees.select{|e| e.name == 'John' && e.salary > 50}.sort_by{|e|
> >> e.age}[2,10]
> >>
> >> #generates "select * from Employees where name = 'John' and salary > 50
> >> order by age limit 2,10"
> >>
> >> employees.select{|e| e.salary < 150}.count
> >>
> >> #generates "select count(*) from Employees where salary < 150
> [...]
> >The ez_where plugin for rails does this.
> >http://brainspl.at/articles/2006/01/30/i-have-been-busy
> 
> Yeah, seems to be close to my proposition.
> What I dislike in the solution (and in Mongoose, which repeats the solution)
> that conditions is NOT plain Ruby, but custom DSL.
> 
> #ez_where:
> 
> articles = Article.ez_find(:all, :include => :author) do |article, author|
>   article.title =~ "%Foo Title%"
>   author.any do
>     name == 'Ezra'
>     name == 'Fab'
>   end 
> end
There's a reason for this, see below
> 
> #my idea, thus lacking knowledge about tables relationships:
> 
> (articles+authors).select{|article, author| 
>    article.author_id == author.id && 
>    article.title =~ "%Foo Title%" && 
>    (author.name == 'Ezra' || author.name == 'Fab')
> }
> 
> Seems to read as "just ruby". 
> What do you think about?
> 
There's a problem:
> (articles+authors).select{|article, author| 
   articles+authors perfectly doable. Same with select
>    article.author_id == author.id && 
     article.authod_id == author.id # doable with appropiate def's of
author_id, #==, id, etc. What's _NOT_ doable is &&. You can't override
that. You have to use another operator or something like any do ... end

>    article.title =~ "%Foo Title%" && 
>    (author.name == 'Ezra' || author.name == 'Fab')
> }
> BTW, I think about some common "over-DSL-ing" between DSL-addict.
> It's something like "Syntactic saccharin"[1] - seems to be "very cool", but
> no added value.
> 
> V.
> 
> 1. http://en.wikipedia.org/wiki/Syntactic_sugar#Syntactic_saccharin
>