I have a PostgreSQL DB, where I use materialized views. The problem occurs when I try to refresh these materialized views.
REFRESH MATERIALIZED VIEW product_cat_mview;
REFRESH MATERIALIZED VIEW productsforproject;
My solution is, when the user want to see updated data, he should click a "refresh button" on the web page, but this takes about 50s (on a local connection and about 2 minutes from the application server) and all this time the user has to wait, which is not good.
Now I should create a solution to automatically refresh these materialized views every 10 minutes. I have created a Java solution with multithreading. But I have one problem.
The first query
REFRESH MATERIALIZED VIEW CONCURRENTLY product_cat_mview;
works correct, but the second
REFRESH MATERIALIZED VIEW CONCURRENTLY productsforproject;
complains that I need to create a unique index. I tried create index, unique index etc. that I found in google, but I still get the message to "Create unique index".
You will have to create a unique index on the materialized view itself.
This would look like this:
CREATE UNIQUE INDEX ON productsforproject (id);
Replace id with a suitable unique key column or a (comma separated) combination of such columns.
The reason for this requirement is that a concurrent refresh works different from a normal refresh: the query is executed, and the existing rows in the materialized view are updated or deleted or new rows inserted based on the query result. The unique index is required to identify which row in the materialized view should be updated or deleted.