Configuring for Materialized Views. Oracle Tips by Burleson Consulting. Oracle materialized views are one of the single most important SQL tuning tools and they are a true silver bullet, allowing you to pre-join complex views and pre-compute summaries for super-fast response time. I've devoted over a hundred pages to SQL tuning with Oracle materialized views in my book "Oracle Tuning: The Definitive Reference ", and also see "Oracle Replication " a deeply-technical book on creating and managing materialized views. Also see my notes now how to identify opportunities for Oracle Materialized Views.
Pure data: when materialized views are converted monalities, re-using implementation techniques, and. discovering. Analysis in Database Applications ". In. Incremental maintenance of views with duplicates. T Griffin, L Libkin Materialized views : techniques, implementations, and applications. IS Mumick. The MIT. Materialized views : techniques, implementations, and applications Gang Luo, V locking protocol for materialized aggregate join views on B-tree indices.
Introduction to Oracle materialized views. Oracle materialized views perform miracles in our goal to reduce repetitive I/O. You want tips on tuning materialized views internal performance, see:. Oracle materialized views were first introduced in Oracle8, and in Oracle materialized views were enhanced to allow very fast dynamic creation of complex objects. Oracle materialized views allow sub-second response times by pre-computing aggregate information, and Oracle dynamically rewrites SQL queries to reference existing Oracle materialized views.
Pure data: when materialized views are converted monalities, re-using implementation techniques, and. discovering. Analysis in Database Applications ". In.
In this article, we continue our discussion of Oracle materialized views and discuss how to set up and configure your Oracle database to use this powerful new feature. We begin with a look at the initialization parameters and continue with details of the effective management and use of Oracle materialized views. Without Oracle materialized views you may see unnecessary repeating large-table full-table scans, as summaries are computed, over and over:.
Perform rewritings in order to execute queries against materialized views. Materialized Views : Techniques, Implementations, and Applications. MIT. Press. Materialized Views : Techniques, Implementations, and Applications [Ashish Gupta, Inderpal Singh Mumick] on Amazon.com. *FREE* shipping on qualifying.
Prerequisites for using Oracle materialized views. In order to use Oracle materialized views, the Oracle DBA must set special initialization parameters and grant special authority to the users of Oracle materialized views. You start by setting these initialization parameters within Oracle to enable the mechanisms for Oracle materialized views and query rewrite, as shown here:. trusted.
Assumes that the Oracle materialized view is current. enforced (default): Always goes to Oracle materialized view with fresh data. stale_tolerated : Uses Oracle materialized view with both stale and fresh data. Next, you must grant several system privileges to all users who will be using the Oracle materialized views. In many cases, the Oracle DBA will encapsulate these grant statements into a single role and grant the role to the end users:. grant query rewrite to scott;.
grant create materialized view to scott;. alter session set query_rewrite_enabled = true;. Invoking SQL query rewrite. Once Oracle materialized views have been enabled, Oracle provides several methods for invoking query rewrite. Query rewrite is generally automatic, but you can explicitly enable it by using I session, alter system, or SQL hints:. ALTER DISABLE QUERY REWRITE.
Select /*+REWRITE(mv1)*/. Refreshing materialized views. In Oracle, if you specify REFRESH FAST for a single-table aggregate Oracle materialized view, you must have created a materialized view log for the underlying table, or the refresh command will fail. When creating an Oracle materialized view, you have the option of specifying whether the refresh occurs manually (ON DEMAND) or automatically (ON COMMIT, DBMS_JOB).
To use the fast warehouse refresh facility, you must specify the ON DEMAND mode. To refresh the Oracle materialized view, call one of the procedures in DBMS_MVIEW. The DBMS_MVIEW package provides three types of refresh operations:. DBMS_MVIEW. REFRESH: Refreshes one or more Oracle materialized views. DBMS_MVIEW.
REFRESH_ALL_MVIEWS: Refreshes all Oracle materialized views. DBMS_MVIEW. REFRESH_DEPENDENT: Refreshes all table-based Oracle materialized views. Manual complete refresh. A complete refresh occurs when the Oracle materialized view is initially defined, unless it references a prebuilt table, and a complete refresh may be requested at any time during the life of the Oracle materialized view. Because the refresh involves reading the detail table to compute the results for the Oracle materialized view, this can be a very time-consuming process, especially if huge amounts of data need to be read and processed. Manual fast (incremental) refresh.
If you specify REFRESH FAST (which means that only deltas performed by UPDATE, INSERT, DELETE on the base tables will be refreshed), Oracle performs further verification of the query definition to ensure that fast refresh can always be performed if any of the detail tables change. These additional checks include the following:. An Oracle materialized view log must be present for each detail table. The RowIDs of all the detail tables must appear in the SELECT list of the MVIEW query definition. If there are outer joins, unique constraints must be placed on the join columns of the inner table. You can use the DBMS_MVIEW package to manually invoke either a fast refresh or a complete refresh, where F equals Fast Refresh and C equals Complete Refresh:. EXECUTE DBMS_MVIEW.
REFRESH('emp_dept_sum','F');. Automatic fast refresh of materialized views. The automatic fast refresh feature is completely new in Oracle, so you can refresh a snapshot with DBMS_JOB in a short interval according to the snapshot log.
With Oracle, it's possible to refresh automatically on the next COMMIT performed at the master table. This ON COMMIT refreshing can be used with materialized views on single-table aggregates and materialized views containing joins only. ON COMMIT MVIEW logs must be built as ROWID logs, not as primary-key logs. For performance reasons, it's best to create indexes on the ROWIDs of the MVIEW. Note that the underlying table for the MVIEW can be prebuilt. Below is an example of an Oracle materialized view with an ON COMMIT refresh.
CREATE MATERIALIZED VIEW.