Postgresql is not being found within my vala project

Question

So I have a project but it is using Vala, it has been so hard finding much within the community but making it through. I have this one project, may be simple but I am find it to be dragging for a long time now.

How do I connect to Postgresql?

I ran the example code online:

using GLib;
using Postgres;


public static int main (string[] args)
{
        string conninfo;

        if (args.length > 1) {
                conninfo = args[1];
        } else {
                conninfo = "dbname = postgres";
        }

        /* Make a connection to the database */
        Database conn = Postgres.connect_db (conninfo);

        /* Check to see that the backend connection was successfully made */
        if (conn.get_status () != ConnectionStatus.OK) {
stderr.printf ("Connection to database failed: %s", conn.get_error_message ());
                return 1;
        }

        /*
         * Our test case here involves using a cursor, for which we must be 
inside
         * a transaction block.  We could do the whole thing with a single
         * PQexec() of "select * from pg_database", but that's too trivial to 
make
         * a good example.
         */

        /* Start a transaction block */
        Result res = conn.exec ("BEGIN");
        if (res.get_status () != ExecStatus.COMMAND_OK) {
                stderr.printf ("BEGIN command failed: %s", 
conn.get_error_message ());
                return 1;
        }

        /*
         * Fetch rows from pg_database, the system catalog of databases
         */
        res = conn.exec ("DECLARE myportal CURSOR FOR select * from 
pg_database");
        if (res.get_status () != ExecStatus.COMMAND_OK) {
                stderr.printf ("DECLARE CURSOR failed: %s", 
conn.get_error_message ());
                return 1;
        }

        res = conn.exec ("FETCH ALL in myportal");
        if (res.get_status () != ExecStatus.TUPLES_OK) {
                stderr.printf ("FETCH ALL failed: %s", conn.get_error_message 
());
                return 1;
        }

        /* first, print out the attribute names */
        int nFields = res.get_n_fields ();
        for (int i = 0; i < nFields; i++) {
                stdout.printf ("%-15s", res.get_field_name (i));
        }
        stdout.printf ("\n\n");

        /* next, print out the rows */
        for (int i = 0; i < res.get_n_tuples(); i++) {
                for (int j = 0; j < nFields; j++) {
                        stdout.printf ("%-15s", res.get_value (i, j));
                }
                stdout.printf ("\n");
        }

        ConnectionOptions opt = Postgres.get_default_options ();
        stdout.printf ("label=%s, keyword=%s\n", opt.label, opt.keyword);

stdout.printf ("db=%s, user=%s, passwd=%s, host=%s, port=%s, tty=%s, options=%s\n", conn.get_db (), conn.get_user (), conn.get_passwd (), conn.get_host (), conn.get_port (), conn.get_tty (), conn.get_options ());

        /* close the portal ... we don't bother to check for errors ... */
        res = conn.exec ("CLOSE myportal");

        /* end the transaction */
        res = conn.exec ("END");

        return 0;
}

however whenever i run

$ valac --pkg libpq test.vala -X -lpq

in the mingw cmd line i get

C:/.../test.vala.c:7:10: fatal error: postgresql/libpq-fe.h: No such file or directory
    7 | #include <postgresql/libpq-fe.h>
      |          ^~~~~~~~~~~~~~~~~~~~~~~
compilation terminated.
Compilation failed: 1 error(s), 0 warning(s)
error: cc exited with status 1

I have been trying many ways to install postgres with pacman -S including

 pacman -S mingw-w64-x86_64-postgresql 

and many other versions of libpq

Answer 1

The error is from the C compiler ( cc ) and is saying it can't find a C header file that's used. The first thing to try is installing the header file, for Arch Linux (which uses pacman ) I believe the libpq-fe.h header file is in the postgresql-devel package.