Re: Returning Vector of Pairs with a PostgreSQL C Extension Function - Mailing list pgsql-general

TalGloz <glozmantal@gmail.com> writes:
> I want to return an vector of pairs using a C extension.

You're going to have to work a lot harder than this:

>         // Return vector of pairs
>         std::vector<std::pair<std::string, std::string>> ret;
>         ret.emplace_back(encodedLocalT1, encodedLocalT2);
>         PG_RETURN_ARRAYTYPE_P(ret);

I do not know what the internal representation of std::vector is in
your C++ library, but it seems highly unlikely that it exactly matches
what Postgres arrays look like.  Nor has Postgres ever heard of a
std::pair.  You'd need to either create a composite type of two text
columns and then build an array of those, or else decide to return a
two-dimensional array to represent this case.  In any case, you must
use Postgres functions to construct the return value; the C++ library
is completely useless for that.

            regards, tom lane