Function lookup_object_oid

src/bin/psql/command.c:5047–5101

* Look up the object identified by obj_type and desc. If successful, * store its OID in *obj_oid and return true, else return false. * * Note that we'll fail if the object doesn't exist OR if there are multiple * matching candidates OR if there's something syntactically wrong with the * object description; unfortunately it can be hard to tell the difference. */

 * object description; unfortunately it can be hard to tell the difference.
 */
static bool
lookup_object_oid(EditableObjectType obj_type, const char *desc,
				  Oid *obj_oid)
{
	bool		result = true;
	PQExpBuffer query = createPQExpBuffer();
	PGresult   *res;

	switch (obj_type)
	{
		case EditableFunction:

			/*
			 * We have a function description, e.g. "x" or "x(int)".  Issue a
			 * query to retrieve the function's OID using a cast to regproc or
			 * regprocedure (as appropriate).
			 */
			appendPQExpBufferStr(query, "SELECT ");
			appendStringLiteralConn(query, desc, pset.db);
			appendPQExpBuffer(query, "::pg_catalog.%s::pg_catalog.oid",
							  strchr(desc, '(') ? "regprocedure" : "regproc");
			break;

		case EditableView:

			/*
			 * Convert view name (possibly schema-qualified) to OID.  Note:
			 * this code doesn't check if the relation is actually a view.
			 * We'll detect that in get_create_object_cmd().
			 */
			appendPQExpBufferStr(query, "SELECT ");
			appendStringLiteralConn(query, desc, pset.db);
			appendPQExpBufferStr(query, "::pg_catalog.regclass::pg_catalog.oid");
			break;
	}

	if (!echo_hidden_command(query->data))
	{
		destroyPQExpBuffer(query);
		return false;
	}
	res = PQexec(pset.db, query->data);
	if (PQresultStatus(res) == PGRES_TUPLES_OK && PQntuples(res) == 1)
		*obj_oid = atooid(PQgetvalue(res, 0, 0));
	else
	{
		minimal_error_message(res);
		result = false;
	}

	PQclear(res);
	destroyPQExpBuffer(query);

	return result;
}

/*
 * Construct a "CREATE OR REPLACE ..." command that describes the specified