const_iterator and const_row_iterator errors in v7.7.2

[CleanHit]

I'm on pqxx v7.7.0 right now and I haven't used for some time. Did anything change regarding iterators in v7.7.2? For example, this works in v7.7.0

std::vector<std::string> output{};
pqxx::result query_result; // this gets populated with a result.
for (pqxx::result::const_iterator iter = query_result.begin(); iter != query_result.end(); iter++)
{
    for (pqxx::const_row_iterator field = iter.begin(); field != iter.end(); field++)
    {
        output.push_back(field.as<std::string>());
    }
}

But fails in v7.7.2 with:

C2079: 'iter' uses undefined class 'pqxx::const_result_iterator'
C2027: use of undefined type 'pqxx::const_result_iterator'
C2677: binary '!=': no global operator found which takes type 'pqxx::result::const_iterator' (or there is no acceptable conversion)

I use:

• Windows 11
• Visual Studio 2022 community edition v17.1.2
• CMake v3.22.3

[jtv]

The main thing that's changed is how libpqxx includes its own headers internally. It could be that your code accidentally fell victim to that. Perhaps your code does an #include <pqxx/foo> which used to in turn do an #include of another header but no longer does.

Could you show us the libpqxx includes at the top of your relevant source file?

[jtv]

And some completely unrelated notes on how to make the code "nicer":

1. Try replacing the for loops with this syntax: for (pqxx::result::const_iterator iter : query_result). Easier on the eyes!
2. Also, try replacing the pqxx::result::const_iterator iter with just auto. It'll figure out the type on its own.
3. If you're querying a lot of rows here, you can speed it up by using pqxx::transaction_base::stream().
4. Converting a field to std::string is pretty inefficient. If performance is a concern here, consider using pqxx::field::view() (when using exec() and pqxx::result) or converting to std::string_view (when using pqxx::transaction_base::stream()).

[CleanHit]

The main thing that's changed is how libpqxx includes its own headers internally. It could be that your code accidentally fell victim to that. Perhaps your code does an #include <pqxx/foo> which used to in turn do an #include of another header but no longer does.

Could you show us the libpqxx includes at the top of your relevant source file?

The .cpp file and the header file have those include

#include <stdexcept>
#include <iostream>
#include <typeinfo>
#include <string>
#include <pqxx/pqxx>

[CleanHit]

And some completely unrelated notes on how to make the code "nicer":

1. Try replacing the `for` loops with this syntax: `for (pqxx::result::const_iterator iter : query_result)`.  Easier on the eyes!

2. Also, try replacing the `pqxx::result::const_iterator iter` with just `auto`.  It'll figure out the type on its own.

3. If you're querying a lot of rows here, you can speed it up by using [pqxx::transaction_base::stream()](https://libpqxx.readthedocs.io/en/stable/a01200.html#aec4d0f102c2c0fab8fa1a48f452abc0f).

4. Converting a field to `std::string` is pretty inefficient.  If performance is a concern here, consider using [pqxx::field::view()](https://libpqxx.readthedocs.io/en/stable/a01044.html#aa05908e8ed320fac8c96b9eb4cf46813) (when using `exec()` and `pqxx::result`) or converting to `std::string_view` (when using `pqxx::transaction_base::stream()`).

Thanks for the tips 😃. This file is relative old and will be refactored at some point.

[jtv]

Looks like <pqxx/pqxx> didn't include all of the headers it needs to include now. Could you try the latest commit on master? I hope it'll fix this.

[CleanHit]

Thanks @jtv, using the master branch resolved the errors.