What is fast refresh on commit?
What is fast refresh on commit?
Fast refresh for a materialized view containing joins and aggregates is possible after any type of DML to the base tables (direct load or conventional INSERT , UPDATE , or DELETE ). It can be defined to be refreshed ON COMMIT or ON DEMAND .
What does a fast refresh means in materialized view?
Materialized views can be refreshed in two ways: fast or complete. A fast refresh requires having a materialized view log on the source tables that keeps track of all changes since the last refresh, so any new refresh only has changed (updated, new, deleted) data applied to the MV.
What does Dbms_mview refresh do?
DBMS_MVIEW. REFRESH: Refreshes one or more Oracle materialized views.
What is the difference between fast refresh and complete refresh in materialized view?
“Complete Refresh” means you truncate entire materialized view and insert new data. “Fast Refresh” means you update (or insert/delete) only the rows which have been changed on master tables.
What are the restrictions for fast refresh materialized view with subqueries?
General Restrictions on Fast Refresh The materialized view must not contain references to non-repeating expressions like SYSDATE and ROWNUM. The materialized view must not contain references to RAW or LONG RAW data types. It cannot contain a SELECT list subquery.
What are the restrictions for fast refresh materialized views with subqueries?
Why materialized view is faster?
Materialized views (MVs) can give amazing performance boost. Once you create one based on your query, Oracle can get the results direct from the MV instead of executing the statement itself. This can make SQL significantly faster.
What is difference between views and materialized views?
Views are generally used when data is to be accessed infrequently and data in table get updated on frequent basis. On other hand Materialized Views are used when data is to be accessed frequently and data in table not get updated on frequent basis.
How does materialized view improve performance in Oracle?
Using Materialized Views to Improve Oracle Database 12c…
- You can perform most DML and query commands such as insert, delete, update, and select.
- They can be partitioned.
- They can be compressed.
- They can be parallelized.
- You can create indexes on them.
Why am I getting the error refresh_fast?
You will get the error on REFRESH_FAST, if you do not create materialized view logs for the master table (s) the query is referring to. If anyone is not familiar with materialized views or using it for the first time, the better way is to use oracle sqldeveloper and graphically put in the options, and the errors also provide much better sense.
Is it possible to fast-refresh MV with min/max after insert?
Unfortunately, as you have noticed, as of 10g a MV that contains MIN or MAX can only be fast-refreshed on commit after insert (so called insert-only MV). The above solution would not work for update/delete (the MV would have to be refreshed manually).
Can I pivot a materialized view on fast refresh?
The pivot command is not available in this Oracle version, and using a GROUP BY + CASE is not allowed on a FAST REFRESH Materialized View. The Materialized View itself looks like this (it contains 700000 rows, the Programmes_Titles table contains 900000 rows):