Postgresql – Postgres Refresh Materialized View Locks

materialized-viewpostgresql

I have a materialized view in Postgres, and want to know what locks (if any) are taken out when refreshing that view.

CREATE TABLE people ( name VARCHAR(30) );
INSERT INTO people VALUES ('Alice'), ('Bob'), ('Cher');
CREATE MATERIALIZED VIEW test AS SELECT * FROM people;
REFRESH MATERIALIZED VIEW test;

Specifically, I'm trying to understand whether the REFRESH MATERIALIZED VIEW command takes out an ACCESS EXCLUSIVE lock.

I tried an explain with no success:

#> EXPLAIN REFRESH MATERIALIZED VIEW test;

                QUERY PLAN                 
-------------------------------------------
Utility statements have no plan structure

Best Answer

REFRESH MATERIALIZED VIEW CONCURRENTLY takes an EXCLUSIVE lock, so SELECTs may still run. Per the manual.

There seems to be an oversight with REFRESH MATERIALIZED VIEW (without CONCURRENTLY) as it's not listed there. A search of the source code shows that ExecRefreshMatView take an ACCESS EXCLUSIVE lock, as you might expect, so no other queries may run on the view.

I've submitted a docs patch to list it.

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