[std.database] at compile time

[Dmitry Olshansky]

On 14.10.2011 19:13, foobar wrote:
> Andrei Alexandrescu Wrote:
>
>> On 10/14/11 6:08 AM, Jacob Carlborg wrote:
>>> On 2011-10-14 12:19, foobar wrote:
>>>> Has anyone looked at Nemerle's design for this?
>>>> They have an SQL macro which allows to write SQL such as:
>>>>
>>>> var employName = "FooBar"
>>>> SQL (DBconn, "select * from employees where name = $employName");
>>>>
>>>> what that supposed to do is bind the variable(s) and it also validates
>>>> the sql query with the database. This is all done at compile-time.
>>>>
>>>> My understanding is that D's compile-time features are powerful enough
>>>> to implement this.
>>>
>>> You cannot connect to a database in D at compile time. You could some
>>> form of validation and escape the query without connecting to the database.
>>
>> A little SQL interpreter can be written that figures out e.g. the names
>> of the columns involved.
>>
>> Andrei
>
> The downsides with writing a separate SQL interpreter are:
>
> a) No connection to the DB means no way to validate the schema, e.g. the db might not even have a 'name' column in the employees table.

The upside is that you can at least rebuild your app when database is 
down or compile it on a separate machine.

> b) No way to validate the SQL per the exact version the DB uses. E.g. LIMIT vs. TOP and also DB vendor specific extensions to SQL syntax.
> c) NIH - implementing your own SQL interpreter when the DB vendor already provides it.
>
> oh, well, perhaps it would be possible with D3 once it supports proper macros. In any case, such a macro probably would be built atop the DB API currently being discussed.


-- 
Dmitry Olshansky