std.database

[Erik Smith via Digitalmars-d]

On Friday, 4 March 2016 at 11:57:49 UTC, Kagamin wrote:
> On Thursday, 3 March 2016 at 18:08:26 UTC, Erik Smith wrote:
>>> db.execute("select from t").reader; //row range
>>> db.execute("select from t").get!long; //scalar
>>> db.execute("select from t"); //non-query
>>
>> More good options (the 3rd one is there).   Also at the value 
>> access level there are several options to consider: 
>> v.get!long, v.as!long, v.to!long, etc.
>
> to!long looks ok.
>
>>> On the other hand execute can simply return the reader with 
>>> extra getter for scalar
>>> result. Just don't do stuff until it's iterated. Is it 
>>> possible?
>>> auto rows = db.execute("select * from t");
>>
>> I'm hedging a bit on this because there are other capabilities 
>> that need to be introduced that might present a problem.
>
> Can you elaborate?

Actually I like this and I think it can work.  I'm trying to keep 
a single execute function name for both row/no-row queries. I can 
still return the range proxy for no-row queries that is either 
empty or throws on access.

> On the other hand these helper methods are built on top of 
> abstraction API and you have to duplicate them in all drivers. 
> Maybe better have them as extension methods in a single module 
> that will work with all drivers? They are effectively a sort of 
> minimal frontend already.

I'm just waiting for the code to settle a bit in a basic working 
state before I refactor into a two layer design.

> The result set is even iterator/stream, i.e. conceptually has 
> even less container properties than ranges themselves. Why 
> would you think of it as a container? I think it's ok as input 
> range. Anyway, this `execute` method is a frontend, i.e. it's 
> replaceable without touching the driver.

The range itself is an InputRange.  The statement is acting as a 
container only in that it is the source of the range and holds 
the data.  I agree that it is confusing to use the term container 
although it seems to fit the definition of one.