如何通过SQL语言查询表、索引、视图的定义？

gaussdb=#  SELECT * FROM pg_get_tabledef('table_name');

gaussdb=#  SELECT oid FROM pg_class WHERE relname='index_name';
gaussdb=#  SELECT * FROM pg_get_indexdef(oid);

gaussdb=#  SELECT viewname, definition FROM pg_views WHERE viewname='view_name';