Re: [boost] SQL: next iteration of sqlpp11

Subject: Re: [boost] SQL: next iteration of sqlpp11
From: Roland Bock (rbock_at_[hidden])
Date: 2014-02-05 17:24:50

On 2014-02-05 22:07, Johan Baltié wrote:
> On Wed, Feb 5, 2014 at 9:57 PM, Roland Bock <rbock_at_[hidden]> wrote:
>>> Maybe if SOCI creates it's own expression grammar for SQL queries it would
>>> be a faster and more practical solution, since SOCI has been around for
>>> quite some time and has solved several issues along the way. And the
>>> expression tree for SQL queries is the fastest part of such a library. The
>>> eye candy and sugar should be easy to convert to string and use the SOCI
>>> engine for it.
>>>
>>> Sqlpp11 will still need to reimplement what SOCI has done several years ago.
>> No. It will not. sqlpp11 will not touch databases, but only glue code...
> I would add that SOCI would still have to handle raw string for SQL,
> because there are things that are specific to one database and cannot
> even be expressed in another DBMS. And we often need them. It's bad to
> say to someone "you have to stuck to the lowest common denominator" if
> he only uses one DBMS.
>
> So, you would have two different syntax for the same library... quite
> strange. Better to split it in 2 differents lib parts like this I
> think.
Not sure if I fully understand your meaning, but here are some
additional comments:

Lowest common denominator:
sqlpp11 builds an expression tree. Whoever interprets the expression
tree can decide how to interpret it and what to accept. So for instance,
sqlpp11 supports outer join (of course), sqlite3 does not. If you give
an expression containing an outer join to the sqlite3 connector, a
static assert will inform you that this won't work. In a multi-database
connector, you might need to replace the static assert by a runtime
exception.

Specific features:
There are quite a few ways to extend sqlpp11. You could add new value
types, or new functions. For example, last November, Dominique Devienne
was asking about array binding for high performance inserts into an
Oracle database. As written in the post that started this thread, that
feature is not part of sqlpp11. But I am convinced that it would be easy
to add a different kind of parameter struct to add the feature.
I don't know if SOCI supports it though, so maybe you would have to use
a different connector.

Can you give me a few examples of the specific things you have in mind?
I probably won't add them to sqlpp11 directly, but I would like to
provide the means to add them without pain.

Cheers,

Roland