由于 table_rewrite
事件的存在,可以实现一个仅允许在维护窗口中重写表的策略。
这是一个实现这种策略的示例。
CREATE OR REPLACE FUNCTION no_rewrite() RETURNS event_trigger LANGUAGE plpgsql AS $$ --- --- Implement local Table Rewriting policy: --- public.foo is not allowed rewriting, ever --- other tables are only allowed rewriting between 1am and 6am --- unless they have more than 100 blocks --- DECLARE table_oid oid := pg_event_trigger_table_rewrite_oid(); current_hour integer := extract('hour' from current_time); pages integer; max_pages integer := 100; BEGIN IF pg_event_trigger_table_rewrite_oid() = 'public.foo'::regclass THEN RAISE EXCEPTION 'you''re not allowed to rewrite the table %', table_oid::regclass; END IF; SELECT INTO pages relpages FROM pg_class WHERE oid = table_oid; IF pages > max_pages THEN RAISE EXCEPTION 'rewrites only allowed for table with less than % pages', max_pages; END IF; IF current_hour NOT BETWEEN 1 AND 6 THEN RAISE EXCEPTION 'rewrites only allowed between 1am and 6am'; END IF; END; $$; CREATE EVENT TRIGGER no_rewrite_allowed ON table_rewrite EXECUTE FUNCTION no_rewrite();
如果您在文档中发现任何不正确、与您特定功能的使用体验不符或需要进一步澄清的地方,请使用此表单来报告文档问题。