Looking into getting near-realtime analytics data from bigquery, and considering costs vs. accuracy, it seems like using materialized view might be a great win.
Considering "near real time" will change to a minimum of 1 minute refresh_interval_minutes, my main concern is that while from documentation it seems that the query will be only on the delta data, the billing will be on the "standard" minimum of 10MB per table.
As I see it, if this minimum is being forced, it dismiss using materialized view as a valid solution for near-realtime.
I would have used "standard" caching over the queries, but caching does not work when querying table with "buffered data", as far as I understand it.
Please advise,
Shushu
The following are key characteristics of BigQuery Materialized Views:
Zero maintenance: A materialized view is recomputed in background once the base table has changed. All incremental data changes from the base tables are automatically added to the materialized views. No user inputs are required.
In other words it means that incremental changes like streaming data into, is automatically added to the materialized view. That means you don't need to set 1 minute refresh period. The maximum refresh frequency cap is 7 days. You could set it to 7 days, or even disable manual refresh as you don't have deletes.
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In our oracle query, I used materialized view to improve the performance and saw a drastic change in performance time of query, response time is in .17 seconds now rather 30 seconds so its working in case we are working on historical data set and need to have one time refresh of materialized view but now requirement is if base table of materialized view would be updating frequently in that case it would be working as the refresh activity of materialized view would be consuming time as well, currently the base table has around 170000 records but in future definitely going to increase so is there any solution or option to resolve this. As i have tried to apply Indexes as well on the table but not able to achieve response time within .17 sec or around the last response time based on index creation was 18 sec.
I have an Oracle materialized view refreshed on demand. Since the view is pretty large, it takes a while to update. I am wondering: when do the updates really become visible to the queries that try read the view? Does RDBMS update the view in a buffer and then makes it visible when update is complete? Or will the changes gradually become visible to the reader? Is this possible to control this?
Materialized views can be refreshed on commit or on demand.
Oracle's documentation is quite good
https://docs.oracle.com/cd/B19306_01/server.102/b14200/statements_6002.htm#i2116410
To have materialized views refresh incrementally you must use the FAST option and you must have materialized view logs to capture changes on the source tables.
If you schedule the demanded refreshes frequently there will be less work to be done for each refresh. If you schedule them less frequently there will be more work to be done. You need to investigate how changes on the source tables are distributed over time to choose well.
Changes will be visible to users when the refresh (whatever size) commits.
I have materialized view in my own schema and the materialized view source is the other schema table but , this master table has 900 rows and i did some dml operations on this master table after that i will refresh this materialized view as you know , and i did some resarch " how can i refresh my own materialized view " and it says " you can do complete refresh or fast refresh " but i didnt understand these solutions meaning so my question is simple ;
What is the difference between complete refresh and fast refresh in MV ?
P.S:If my master table has 1 million or more rows , which one i should choose? (fast or complete)
Thank you for your reply.
"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.
And just as information "Force Refresh" mean, Oracle tries to make a Fast Refresh and if this is not possible then do "Complete Refresh"
Usually Fast Refresh is much faster than Complete Refresh but it has restrictions. You have to define MATERIALIZED VIEW LOG on master tables.
Here is a full list of restrictions General Restrictions on Fast Refresh, there are quite many.
As always it depends, so if possible try both and measure for your application. As a general rule the fast refresh is likely to be much faster provided that only a small part of the data has changed. If all the data has changed a complete refresh is better.
With the fast refresh Oracle keeps track of the changes for the base tables and applies the changes to the materialized view when it is refreshed. A complete refresh on the other hand rebuilds the materialized view from scratch. With millions of rows that will be expensive, but again it is impossible to pick the best option without knowing more about your application.
We have to create a materialised view in our database from a remote database which is currently in production. The view has about 5 crore records and is taking a long time. In between , the connection has snapped once and not even a single record persisted in our database. Since the remote database is production server, we get a very limited window to create the view.
My question is, can we have something like auto commit /auto start from where left at last time while the view is created so that we don't have to do the entire operation in one go ?
We are tying to make the query such that records can be fetched in smaller numbers as a alternate. But the data is read only for us and doesn't really have a where clause at this point which we can use.
Due to sensitive nature of data, I cannot post the view structure or the query.
No, you can not commit during the process of creating the view. But why don't you import the data to a table instead of a view? This would provide the possibility to commit in between. Furthermore this might provide the possibility, to load only the delta of changes maybe on daily basis - this would reduce the required time dramatically.
I have a table on master site which only allow insert operation. I want to replicate the rows which are inserted recently so, need something which can track the last record replicated into the local site and perform the replication afterwards.
I have tried Oracle materialized view but still confuse that whether I use the Fast Refresh or Complete Refresh. I need all the newly inserted rows replicated in one transaction.
Are there any better approach to do that? Any help would be highly appreciated.
Thanks.
A fast refresh would copy incremental changes over the network but requires that a materialized view log be created on the master site on the source table. That adds some overhead to the inserts happening on the master table but would generally make the refresh more efficient.
A complete refresh would copy every row over the network every time the materialized view is refreshed. That is likely to be less efficient from a refresh perspective but there will be no overhead to inserts on the source table and the master site does not need to create a materialized view log.
Oracle provides a host of data replication technologies-- materialized views are the oldest and probably the least efficient but are relatively trivial to set up. Streams is a newer technology that has much lower overhead but is quite a bit more complex to set up. Golden Gate is the preferred replication technology today but that has extra licensing costs.