ReQL: pluses and minuses of pipeline-style queries

[Rikki Cattermole via Digitalmars-d]

On 27/04/2015 1:12 a.m., Idan Arye wrote:
> On Sunday, 26 April 2015 at 01:03:12 UTC, Rikki Cattermole wrote:
>> I'm personally moving towards a DSL.
>>
>> unittest {
>>     auto myQuery = """
>> using webdev.base.orm.query.parser.defs # allow for D class name
>> instead of table name
>> ; # end of \"sentence\"
>>
>> from MyModel
>> where key == $0
>> as simple
>> # as index # but only one can be defined, two in total internal
>> ; # end of \"sentence\"
>>
>> from MyModel
>> where value contains $0
>> as complex
>> # as index # but only one can be defined, two in total internal
>> ; # end of \"sentence\"
>>
>> """.query;
>>
>>     MyModel[] gotValues = myQuery.simple("test");
>>     gotValues = myQuery.perform("complex", "another");
>> }
>>
>> Pros:
>> - Runtime reloadability
>> - Runtime composability
>> - More flexible
>> Cons:
>> - It's a string
>
> I get why people want to use a DSL based on the host language's
> constructs. The host language is built to deal with it's own constructs,
> so composing your queries from them allows you to easily do stuff like
> store query parts in variables, create functions that modify queries,
> use reflection on the queries, send variables and expressions from the
> host process directly to the query etc.
>
> What do you gain from a string-based DSL? It doesn't allow you to do any
> of these things - at least not any more conveniently/efficiently/safely
> than you could with SQL strings - so essentially it's just a language to
> replace SQL.
>
> Now, Some languages are so messed up that it's worthwhile to create a
> language the compiles to them(*cough* Javascript *cough*). SQL is not
> one of them. Even if we assume this language is better than SQL - is the
> difference enough to justify leanring this new language, to translate
> SQL errors caused by misuse of that langauge(or propagate and let the
> user deal with it), and deal with errors caused by bad implementation of
> the translation?

Worse case scenario, you are free to use the raw sql function for a 
query. But it will only work if its for an SQL database engine.
Also this won't compile to D.