In Oracle 19c database, when we drop a table what happens to the procedures, triggers, index that uses this table?
Will the triggers, procedures, index gets dropped automatically or
will it become INVALID status?
I want to know what is the correct process that needs to be
followed while dropping the table when you know you already have
the triggers, procedures, index associated with that particular
table?
Please help me out.
Indexes and triggers on the table will be dropped (as will grants)
Synonyms and views will become invalid
Hard-coded references to the table in procedures, packages, functions and triggers will make them invalid. References via dynamic SQL won't result in invalidation, but would fail when executed.
Query the DBA_DEPENDENCIES view to see which objects have dependencies and will get invalidated. There can be knock on impacts (dropping a table invalidates a procedure and a package that calls that procedure will be invalidated even if it doesn't reference the table directly).
If all usages are within the same user/schema, you can query USER_DEPENDENCIES instead. Don't bother with ALL_DEPENDENCIES view as, if another user has created objects referencing the victim table, you might not have privileges to see that object anyway.
Related
I have a oracle view it returns 5 million records from different tables and i use this view to insert into different tables using a single procedure, inside this procedure i use this several times and this is affecting the performance, is there any way we can query the view once and later i can use it multiple places?
A view is a stored query; itself, it doesn't contain any data. If its code is complex and fetches data from several tables, using different conditions, aggregations, whatnot, it can take some time to access data.
In your situation, maybe a global (or private; depending on Oracle version you use) temporary table (GTT) would help.
you create it once
at the beginning of the procedure, insert data from the view into it
the rest of the procedure would work with those prepared data
once the session (or transaction; depending on how you set the GTT up) is over, data from the table is lost
the table can be reused next time you run the procedure
It occurred to me that I have a fundamental issue with respect to privileges.. Anyone who is granted access to my data warehouse, will be given privileges to objects in the reporting schema. However, whenever we drop objects, those privileges are lost.
The fundamental requirements that should be met with the approach are:
Indexes not populated during load of data (dropped, disabled?) to avoid populating while inserting
Retain existing privileges.
What do you guys think is the best approach based on the requirements above?
For requirement 1: depending on the version of Oracle you're running, you may be able to alter the indexes as invisible. Making indexes invisible will cause the optimizer to ignore them, but it can come in handy because you can simply make them visible again after whatever operation you're performing. If that won't work, you could alter them unusable instead. More info here: https://oracle-base.com/articles/11g/invisible-indexes-11gr1
For requirement 2: Once an object is dropped, the privileges are dropped along with it. There's not really any straightforward way to retain the grants as they are when an object is dropped, however, you could use a number of different methods to "save" the privileges when a table is dropped. These are just some ideas to get you going, not a guaranteed method of success.
Method 1: Using Triggers and DBMS_SCHEDULER to issue the grants. Triggers can be very powerful, and if you create a trigger that is set to run when a table of a specific name is created under a specific schema, you can use DBMS_SCHEDULER to run a job that will issue the missing grants.
Method 2: Per Littlefoot's suggestion, you can save the grant statements in a SQL script and run it manually every time the table is created (or create a trigger for it!)
Method 3: Work with the business and implement a process wherein the table does not need to be dropped, and instead is altered to fit business needs. To use this method, you'll have to understand why the object is being dropped in the first place. Is a drop really necessary to accomplish the desired outcome? I've seen teams request that tables be dropped when they really just wanted the tables to be truncated. If this is one of those scenarios, truncating instead of dropping will let you keep the object and its grants intact.
In any scenario, you'll also want to make sure that you are managing permissions via roles whenever possible, rather than issuing grants to individual users/schemas. Utilizing roles will make managing permissions a lot easier in just about any scenario.
If you DROP an object, the grants are gone. However:
Indexes not populated during load of data (dropped, disabled?) to avoid
populating while inserting
Retain existing privileges.
Here is one common approach. There are others. If you have partitioning there are better ways.
ALTER INDEX my_index1 UNUSABLE;
ALTER INDEX my_index2 UNUSABLE;
...
ALTER INDEX my_indexn UNUSABLE;
TRUNCATE TABLE my_table_with_n_indexes; -- OPTIONAL (depends if you need to start empty)
INSERT /*+ APPEND */ INTO my_table_with_n_indexes; -- Do your load here. APPEND hint optional, depending on what you are doing
ALTER INDEX my_index1 REBUILD;
ALTER INDEX my_index2 REBUILD;
...
ALTER INDEX my_indexn REBUILD;
Let's say I created a table test_table in development just to test a trigger, this trigger would then be reused in many other tables (future and existing).
So I code the trigger, test it, all good! But at the moment, if I want to replicate it, I will have to copy it from test_table's triggers and edit it.
So if someone deletes the table accidentally, the trigger is gone, and I don't have it saved nowhere else. Or if I just want to delete random test tables in our database, I can't.
What's a recommended way to save a trigger as a "template" in oracle? So I can reuse it in other tables and have it not be dependant of a random test table, or any table.
There are a lot of ways you can keep a copy of your TRIGGER SQLText.
Here's a few examples.
In Version Control:
You can use any of the many version control tools to maintain a versioned history for any code you like, including SQL, PL/SQL, etc. You can rewind time, view differences over time, track changes to the template, even allow concurrent development.
As a Function:
If you want the template to live in the database, you can create a FUNCTION (or PACKAGE)that takes as parameters the target USER and TABLE, and it replaces the USER and TABLE values in its template to generate the SQLTEXT required to create or replace the template TRIGGER on the target TABLE. You can make it EDITIONABLE as needed.
In a Table:
You can always just create a TABLE that holds template TRIGGER SQLText as a CLOB or VARCHAR2. It would need to be somewhere where it isn't likele to be "randomly" deleted, though. You can AUDIT changes to the TABLE's data, to see the template change over time. Oracle has tons of auditing options.
In the logs:
You can just log (all) DDL out. If you ENABLE_DDL_LOGGING, the log xml will have a copy of every DDL statement, categorized, along with when and where it came from.
I currently have 2 schemas, A and B.
B has a table, and A executes selects inserts and updates on it.
In our sql scripts, we have granted permissions to A so it can complete its tasks.
grant select on B.thetable to A
etc,etc
Now, table 'thetable' is dropped and another table is renamed to B at least once a day.
rename someothertable to thetable
After doing this, we get an error when A executes a select on B.thetable.
ORA-00942: table or view does not exist
Is it possible that after executing the drop + rename operations, grants are lost as well?
Do we have to assign permissions once again ?
update
someothertable has no grants.
update2
The daily process that inserts data into 'thetable' executes a commit every N insertions, so were not able to execute any rollback. That's why we use 2 tables.
Thanks in advance
Yes, once you drop the table, the grant is also dropped.
You could try to create a VIEW selecting from thetable and granting SELECT on that.
Your strategy of dropping a table regularly does not sound quite right to me though. Why do you have to do this?
EDIT
There are better ways than dropping the table every day.
Add another column to thetable that states if the row is valid.
Put an index on that column (or extend your existing index that you use to select from that table).
Add another condition to your queries to only consider "valid" rows or create a view to handle that.
When importing data, set the new rows to "new". Once the import is done, you can delete all "valid" rows and set the "new" rows to "valid" in a single transaction.
If the import fails, you can just rollback your transaction.
Perhaps the process that renames the table should also execute a procedure that does your grants for you? You could even get fancy and query the dictionary for existing grants and apply those to the renamed table.
No :
"Oracle Database automatically transfers integrity constraints, indexes, and grants on the old object to the new object."
http://download.oracle.com/docs/cd/B19306_01/server.102/b14200/statements_9019.htm#SQLRF01608
You must have another problem
Another approach would be to use a temporary table for the work you're doing. After all, it sounds like it is just the data is transitory, at least in that table, and you wouldn't keep having to reapply the grants each time you had a new set of data/create the new table
In context of Oracle 9i database, usually for a view to be created an underlying base table is mandatory, however this constraint can be violated if the FORCED clause is used while creating the view.
What is the significance of these views if their base tables does not exist?
In which conditions these views will be of help?
you would use the FORCE keyword if you are creating several views that reference each other and you don't want to spend time to determine in which order they should be created.
See also:
streamlining creating of packages and views
On a large project this can be very useful: I create a table, someone else creates a packaged function, and you create a view that accesses the table and the packaged function. We then all put our DDL into the source control / release system and the DBA installs all the code on the test / production system. The FORCE keyword ensures that the view gets created, though possibly in an invalid state, even if its DDL is run before the table and/or package DDL.