自动加载视图

Question

Can we create Materialized view in mysql or sql which will automatically reloaded with the data from the underlying bases table without hitting the base table.

Elobration:

I have created viewMasterTable view which is join of 3 tables,

TableA,TableB,Table = viewMasterTable

Now i want this view to be reloaded with the data if any changes ie upadate,insert or delete is made on the base table without hitting the base table.

**Will this view concept will help in performance increase**

Answer 1

You can create materialized views in SQL-Server Enterprise Edition. In MySQL you cannot create materialized views. Thus this only applicable to SQL-Server and a very specific edition.

Now you don't get something for nothing. If you materialize a view it means that the source columns used in the base table(s) have to remain in synchronization with the data in the base tables. Thus any updates/inserts/deletes on the base table will be impacted as the server now has to write to the base tables and update the view. So you will have an extra operation to complete for every write this will incur a performance penalty on the server itself. Depending on size of tables, views and frequency of updates this might or might not be a small penalty.

You can index materialized views and this is where the power really shines. Say you have a very complex view that can be filtered by various columns a materialize view will allow you to index the fields in the view allowing a user to filter much faster. However the downside is that for every index that you create on a materialized view it will incur more write penalties as the server needs to update indexes when updating the view.

So while it can be a really good way to increase performance for reads on a complex query you will see a performance penalty on writes. How bad will this penalty be? Well that depends on how you have arranged your Disk IO pathways ie for example placing your indexes, views and tables on separate physical spindles will help alleviate some of the write overhead.