Add tests for loading the catalog

pglablib/catalog/PgDatabaseSizes.cpp

@@ -0,0 +1,25 @@
+#include "PgDatabaseSizes.h"
+
+#include "Pgsql_Result.h"
+
+PgDatabaseSizes loadDatabaseSizes(Pgsql::Connection &connection)
+{
+	std::string q =
+		"SELECT pg_database.oid, "
+		"  case when has_database_privilege(current_role, pg_database.oid, \n"
+		"    'connect') then pg_database_size(pg_database.oid) else -1 end \n"
+		"FROM pg_database";
+
+	Pgsql::Result sizesResult = connection.query(q.c_str());
+
+	PgDatabaseSizes result;
+	result.reserve(sizesResult.rows());
+	for (auto& row : sizesResult)
+	{
+		PgDatabaseSize ds;
+		ds.oid = row.get(0);
+		ds.totalBytes = row.get(1);
+		result.push_back(ds);
+	}
+	return result;
+}