Function StoreQueryTuple

src/bin/psql/common.c:761–816

* StoreQueryTuple: assuming query result is OK, save data into variables * * Returns true if successful, false otherwise. */

 * Returns true if successful, false otherwise.
 */
static bool
StoreQueryTuple(const PGresult *result)
{
	bool		success = true;

	if (PQntuples(result) < 1)
	{
		pg_log_error("no rows returned for \\gset");
		success = false;
	}
	else if (PQntuples(result) > 1)
	{
		pg_log_error("more than one row returned for \\gset");
		success = false;
	}
	else
	{
		int			i;

		for (i = 0; i < PQnfields(result); i++)
		{
			char	   *colname = PQfname(result, i);
			char	   *varname;
			char	   *value;

			/* concatenate prefix and column name */
			varname = psprintf("%s%s", pset.gset_prefix, colname);

			if (VariableHasHook(pset.vars, varname))
			{
				pg_log_warning("attempt to \\gset into specially treated variable \"%s\" ignored",
							   varname);
				continue;
			}

			if (!PQgetisnull(result, 0, i))
				value = PQgetvalue(result, 0, i);
			else
			{
				/* for NULL value, unset rather than set the variable */
				value = NULL;
			}

			if (!SetVariable(pset.vars, varname, value))
			{
				free(varname);
				success = false;
				break;
			}

			free(varname);
		}
	}

	return success;
}