Re: [boost] [rdb] 0.04

Subject: Re: [boost] [rdb] 0.04
From: Jean-Louis Leroy (jl_at_[hidden])
Date: 2009-09-21 19:03:19

> struct A{
>   bool have_value;
>   B b;
> 
>   void serialize(Ar &ar){
>     ar & have_value;
>     if(have_value) ar & b;
>   }
> };
> 
> that's valid serialization code and introduces a new table column at runtime 
> if the object is mapped to a rdb and only objects with !have_value have been 
> serialized so far.

True, fully static approaches will create the column even if it's never 
used.

> how did you plan to represent views generated by a SELECT query? because the 
> query results can contain columns from different tables so you'd have to have 
> a "dynamic" row type anyway. (unless you tried to deduce the row type from 
> the query type?)

Exactly. My `select' construct remembers all the types that were 
presented to it. Constructs like views and subselects will be statically 
  checked. Errors like using in the `values' clause a column from 
another table in an insert statement, or a column from the same table 
but of the wrong type are also caught at compile-time. I guess that one 
could also make a compile-time assertion that validates an entire schema.

J-L