Hi, I propose to acquire SI-read predicate locks on materialized views as the attached patch. Currently, materialized views do not participate in predicate locking, but I think this causes a serialization anomaly when `REFRESH MATERIALIZED VIEW CONCURRENTLY` is used. For example, supporse that there is a table "orders" which contains order information and a materialized view "order_summary" which contains summary of the order information. CREATE TABLE orders (date date, item text, num int); CREATE MATERIALIZED VIEW order_summary AS SELECT date, item, sum(num) FROM orders GROUP BY date, item; "order_summary" is refreshed once per day in the following transaction. T1: REFRESH MATERIALIZED VIEW CONCURRENTLY order_summary; "orders" has a date column, and when a new item is inserted, the date value is determined as the next day of the last date recorded in "order_summary" as in the following transaction. T2: SELECT max(date) + 1 INTO today FROM order_summary; INSERT INTO orders(date, item, num) VALUES (today, 'apple', 1); If such two transactions run concurrently, a write skew anomaly occurs, and the result of order_summary refreshed in T1 will not contain the record inserted in T2. On the other hand, if the materialized view participates in predicate locking and the transaction isolation level is SELIALIZABLE, this anomaly can be avoided; one of the transaction will be aborted and suggested to be retried. The problem doesn't occur when we use REFRESH MATERIALIZED VIEW (not CONCURRENTLY) because it acquires the strongest lock and any concurrent transactions are prevent from reading the materialized view. I think this is the reason why materialized views didn't have to participate in predicate locking. However, this is no longer the case because now we support REFRESH ... CONCURRENTLY which refreshes the materialized view using DELETE and INSERT and also allow to read it from concurrent transactions. I think we can regard them as same as DELETE, INSERT, and SELECT on regular tables and acquire predicate locks on materialized views as well. What do you think about it? Regards, Yugo Nagata -- Yugo NAGATA <nagata@sraoss.co.jp>