Re: Returning Vector of Pairs with a PostgreSQL C Extension Function

TalGloz <glozmantal(at)gmail(dot)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&lt;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