How much space do VIEWS occupy in PostgreSQL?

Question

If I store my query results as views does it take more space of my memory in comparison to a table with query results?

Another question about views is that can I have new query based on the results of a query that is stored as views?

Answer 1

Views don't store query results, they store queries.

Some RDBMS allow the way to store query results (for some queries): this is called materialized views in Oracle and indexed views in SQL Server.

PostgreSQL does not support those (though, as @CalvinCheng mentioned, you can emulate those using triggers or rules).

Yes, you can use views in your queries. However, a view is just a convenient way to refer to a complex query by name, not a way to store its results.

Answer 2

For Question 1

To answer your first question, you cannot store your query results as views but you can achieve a similar functionality using PostgreSQL's trigger feature.

PostgreSQL supports creation of views natively but not the creation of materialized views (views that store your results) - but this can be handled using triggers. See http://wiki.postgresql.org/wiki/Materialized_Views

views do not take up RAM ("memory").

For Question 2

And to answer the second question, to update a view in postgresql, you will need to use CREATE RULE - http://www.postgresql.org/docs/devel/static/sql-createrule.html

CREATE RULE defines a new rule applying to a specified table or view. CREATE OR REPLACE RULE will either create a new rule, or replace an existing rule of the same name for the same table.

Answer 3

I would like to point out that as of Postgres 9.3, Materialized Views are supported