Re: boost.sqlite

From: Marshall Clow (mclow.lists_at_[hidden])
Date: 2024-01-06 16:15:17

On Jan 6, 2024, at 7:50 AM, Ruben Perez via Boost <boost_at_[hidden]> wrote:
> 
>> 
>>> [...] use one connection per thread
>> 
>> Yes, this is likely the best approach in most cases. You might also
>> consider a connection pool. Could a generalised connection pool be
>> something of value in Boost? I may have mentioned this before in
>> relation to MySQL.
> 
> Boost.MySQL has recently added dedicated connection_pool functionality.
> I don't see how sqlite and MySQL could share pooling functionality, since
> one is sync and the other is async. Additionally, efficient pooling
> relies on database-specific details, which are not exposed
> to the end user but are used internally to boost performance.
> 
>> 
>> On another subject, I note that the proposed API extensively uses
>> string_view as a function return type. For example, field::column_name()
>> returns a string_view. I consider this an anti-pattern. (In case anyone
>> doesn't understand the issue, the danger is that the view will be
>> dangling if the caller keeps it beyond the life of... some other object;
>> I was going to write "the field object", but I'm not sure if that's
>> right; maybe the row? The docs don't say.) In the case of e.g. column_name(),
>> std::string's small buffer optimisation means that returning a std::string
>> will not involve dynamic allocation unless the column name is more than
>> maybe 23 characters long, which surely must be sufficient in practically
>> all cases. If you really worry about long column names, please have a
>> separate method (e.g. column_name_view()) whose name is a warning that
>> it returns a view.
> 
> MSVC standard lib and stdlibc++ std::string's have 15 characters of
> static capacity.

libc++’s SSO string holds 22 chars on a 64 bit platforms.

— Marshall

#include <iostream>
#include <string>

int main () {
        std::cout << sizeof (std::string) << std::endl;
        
        std::string s;
        for (int i = 0; i < 30; ++i) {
                s.push_back(' ');
                std::cout << s.size() << "  " << s.capacity() << std::endl;
        }
}