I have a database running under Sql server 2005 with merge replication. I want to change some of the FK columns to be 'not null' as they should always have a value. SQL server won't let me do that though, this is what it says:
Unable to modify table. It is invalid to drop the default constraint
on the rowguid column that is used by
merge replication. The schema change
failed during execution of an internal
replication procedure. For corrective
action, see the other error messages
that accompany this error message. The
transaction ended in the trigger. The
batch has been aborted.
I am not trying to change the constraints on the rowguid column at all, only on another column that is acting as a FK. Other columns I want to set to be not null because the record doesn't make any sense without that information (i.e. on a customer, the customer name).
Questions:
Is there a way to update columns to be 'not null' without turning off replication then turning it back on again?
Is this even the best way to do this - should I be using a constraint instead?
Apparently SSMS makes changes to tables by dropping them and recreating them. So just needed to make the changes using T-SQL statement.
ALTER TABLE dbo.MyTable ALTER COLUMN MyColumn nvarchar(50) NOT NULL
You need to script out your change in T-SQL statements as SQL Server Management Studio will look to drop and re-create the table, as opposed to simply adding the additional column.
You will also need to add the new column to your Publications.
Please note that changing a column in this manner can be detrimental to the performance of Replication. Dependent on the size of the table you are altering, can lead to a lot of data being replicated. Consider that although your table modification can be performed in a single statement, if 1 million rows are affected then 1 million updates will be generated at the Subscriber, NOT a single update statement as is commonly thought.
The hands on, improved performance approach.......
To perform this exercise you need to:
Backup your Replication environment by scripting out your entire configuration.
Remove the table from Replication at
both Publishers/Subscribers
Add the column at each
Publisher/Subscriber.
Apply the Update locally at each
Publisher/Subscriber.
Add the table back into Replication.
Validate that transactions are being
Replicated.
Related
I have a table with quite many rows (more than 300 000 000). I want to remove not null constraint for one of the columns by running the next SQL query while the database is still under load (since the table is big, it may take about 10 minutes):
ALTER TABLE DECLARATION
ALTER COLUMN LOCAL_REFERENCE_NUMBER VARCHAR(22) NULL WITH (ONLINE = ON);
I expect this ONLINE = ON option to ensure that the table is not locked during the update to make sure that the applications that use the database can still do it during the update.
However, the docs say that ONLINE = ON is only applicable for adding and removing indexes as well as primary key or unique constraints, i.e., as it seems from the official documentation, this option has no effect for the not null constraints.
Is it indeed the case, or the documentation is just not full? If that is the case, what is so special about dropping not null constraints that it cannot be done online?
Thank you.
As stated in commment section this operation should be metadata operation only(if no data type changes occured):
ALTER TABLE DECLARATION
ALTER COLUMN LOCAL_REFERENCE_NUMBER VARCHAR(22) NULL;
It could be verified by setting Extended Event session and observing sqlserver.compressed_alter_column_is_md_only event (SQL Server 2016+)
I'm using SQL Server 2012 Express and since I'm really used to PL/SQL it's a little hard to find some answers to my T-SQL questions.
What I have: about 7 tables with distinct columns and an additional one for logging inserted/updated/deleted values from the other 7.
Question: how can I create one trigger per table so that it stores the modified data on the Log table, considering I can't used Change Data Capture because I'm using the SQL Server Express edition?
Additional info: there is only two columns in the Logs table that I need help filling; the altered data from all the columns merged, example below:
CREATE TABLE USER_DATA
(
ID INT IDENTITY(1,1) NOT NULL,
NAME NVARCHAR2(25) NOT NULL,
PROFILE INT NOT NULL,
DATE_ADDED DATETIME2 NOT NULL
)
GO
CREATE TABLE AUDIT_LOG
(
ID INT IDENTITY(1,1) NOT NULL,
USER_ALTZ NVARCHAR(30) NOT NULL,
MACHINE SYSNAME NOT NULL,
DATE_ALTERERED DATETIME2 NOT NULL,
DATA_INSERTED XML,
DATA_DELETED XML
)
GO
The columns I need help filling are the last two (DATA_INSERTED and DATA_DELETED). I'm not even sure if the data type should be XML, but when someone either
INSERTS or UPDATES (new values only), all data inserted/updated on the all columns of USER_DATA should be merged somehow on the DATA_INSERTED.
DELETES or UPDATES (old values only), all data deleted/updated on the all columns of USER_DATA should be merged somehow on the DATA_DELETED.
Is it possible?
Use the inserted and deleted Tables
DML trigger statements use two special tables: the deleted table and
the inserted tables. SQL Server automatically creates and manages
these tables. You can use these temporary, memory-resident tables to
test the effects of certain data modifications and to set conditions
for DML trigger actions. You cannot directly modify the data in the
tables or perform data definition language (DDL) operations on the
tables, such as CREATE INDEX. In DML triggers, the inserted and
deleted tables are primarily used to perform the following: Extend
referential integrity between tables. Insert or update data in base
tables underlying a view. Test for errors and take action based on the
error. Find the difference between the state of a table before and
after a data modification and take actions based on that difference.
And
OUTPUT Clause (Transact-SQL)
Returns information from, or expressions based on, each row affected
by an INSERT, UPDATE, DELETE, or MERGE statement. These results can be
returned to the processing application for use in such things as
confirmation messages, archiving, and other such application
requirements. The results can also be inserted into a table or table
variable. Additionally, you can capture the results of an OUTPUT
clause in a nested INSERT, UPDATE, DELETE, or MERGE statement, and
insert those results into a target table or view.
Just posting because this is what solved my problem. As user #SeanLange said in the comments to my post, he said to me to use an "audit", which I didn't know it existed.
Googling it, led me to this Stackoverflow answer where the first link there is a procedure that creates triggers and "shadow" tables doing sort of what I needed (it didn't merge all values into one column, but it fits the job).
I need a simple resize of a column from VARCHAR(36) to VARCHAR(40).
If you try to use SQL Server Enterprise Manager, the script it generates is effectively creating a new table with the new structure, inserting all of the data from the existing table into it, dropping the existing table, renaming the new table, and recreating any indexes.
If you read the documentation (and many online resources including SO), you can use an ALTER statement for the resize.
Does the ALTER affect the way the data is stored in any way? Indexes? Statistics? I want to avoid performance hits because of this modification due to the fact that the table can get large.
Just use ALTER TABLE. SSMS is a bit, er, stupid sometimes
You'll need to drop and recreate dependent constraints (FK, unique, index, check etc)
However, this is only a metadata change and will be very quick for any size table (unless you also change NOT NULL to NULL or varchar to nvarchar or such)
No, ALTER TABLE (http://msdn.microsoft.com/de-de/library/ms190273.aspx) is the way how Microsoft intended to do this kind of change.
And if you do not add extra options to your command, no indexes or statistics should get harmed.
A possibility of data loss is also not given, because you are just making the column bigger.
Everything should be fine.
Changes to database structure should NEVER be made using SSMS on a porduction environment for just the reason you brought up. It can destroy performance in a large table. ALTER table is the prefered method, it is faster and it can be stored in source control as a change to push to prod after testing.
Following should be the better way to handle this
IF EXISTS (SELECT 1
FROM INFORMATION_SCHEMA.COLUMNS
WHERE TABLE_NAME = '<tablename>'
AND COLUMN_NAME = '<field>')
BEGIN
ALTER TABLE <tablename> ALTER COLUMN [<field>] varchar(xxxx) null
END
ELSE
I'm trying to insert a few thousand rows into a table in a database that is replicated across two servers. From either the publisher or the subscriber, I get the same error:
Msg 548, Level 16, State 2, Line 1
The insert failed. It conflicted with an identity range check constraint in database 'XXX', replicated table 'dbo.NODE_ATTRIB_RSLT', column 'ID'. If the identity column is automatically managed by replication, update the range as follows: for the Publisher, execute sp_adjustpublisheridentityrange; for the Subscriber, run the Distribution Agent or the Merge Agent.
The statement has been terminated.
Checking the constraint on the table, it seems to me like I should be able to insert at least 1000 rows at a time before running into issues. However, I get the same error when trying to insert just a few tens of rows!
Here's how I'm trying to insert data:
insert into NODE_ATTRIB_RSLT
([NODE_ID]
,[ATTRIB_ID]
,[STATE_ID]
,[PLAN_REVISION_ID]
,[TIMESTAMP]
,[VALUE]
,[VALUE_TEXT]
,[LAST_MODIFIED])
SELECT [NODE_ID]
,[ATTRIB_ID]
,[STATE_ID]
,[PLAN_REVISION_ID]
,[TIMESTAMP]
,[VALUE]
,[VALUE_TEXT]
,[LAST_MODIFIED] FROM [NODE_ATTRIB_RSLT_TEMP]
The PK column is an autogenerated identity called ID. To try to insert fewer rows at a time I've added a WHERE clause at the end of the select like so:
WHERE ID >= 1000 and ID <1100
but to no avail.
Running sp_adjustpublisheridentityrange on the Publisher executes successfully but has no effect.
How can I fix this problem with inserts?
How can I modify the ranges of the indentity range contraints to a more reasonable level while leaving the replication running?
I think I worked out what the problem was.
Looking at the properties for the replicated table, it had the standard default identity range of 10000 for the Publisher and 1000 for the Subcriber.
However, checking the identity constraint on the actual table (using SP_HELPCONSTRAINT 'node_attrib_rslt') revealed that there was only a pool of 1000 IDs on both servers. This made the bulk insert fail even when I restricted the number of rows to insert - I'm guessing SQL Server doesn't even get that far when it checks the constraint when running an INSERT INTO.
To fix it I had to do several things:
Change the identity range of the table. I set it up to 20K for both Publisher and Subcriber.
On the Publisher, expand Replication --> Local Publications
Right-click the particular subscription and choose Properties.
Select the Articles page.
Highlight the appropriate Table.
Click on the Article Properties 'button', and choose 'Set Properties of Highlighted Table Article'.
In the Article Properties window, look for Identity Range Management options.
Change the appropriate values.
Press OK and OK on the dialog windows.
Run the sp_adjustpublisheridentityrange stored proc on the Publisher.
New query window on the server
Choose the correct database
Execute sp_adjustpublisheridentityrange #table_name = 'node_attrib_rslt'
From the subcriber, force-synchronise the servers.
On the Subscriber, expand Replication --> Local Subcriptions
Right-click the particular subscription and choose View Subscription Status.
In the dialog that appears, press the monitor button.
In the Replication Monitor window that appears, expand the particular Publisher in the left hand pane.
Click on the Subcription to edit.
In the right hand pane, right-click on the subcription status and choose Start Synchronising.
The status should update to 'Synchronising' while it does its thing.
After it's finished, click on the 'Warnings and Agents' tab. I had a 'Snapshot Agent' listed in the lower pane. Right click on that Agent and start it. After it had been running for a while, the change of properties on the server should have migrated to the client.
Maybe: insert some test rows into the table.
Edit: I've had to do this task again recently, and the constraint on the table would not update until I inserted a bunch of dummy data into the table so as to exhaust the default constraint. Then I resyncronised the servers, and the constraint was updated to the new value.
After that, checking the identity constraint revealed that I finally had a 20K ID range to insert with on both the Publisher and the Subcriber.
I had this exact same issue, and the above solution didn't do anything for me.
Instead what ended up solving the issue was by setting the new, larger identity ranges on the tables in the publication, and then dropping the identity constraints on the table
And then finally running this command that sets the current identity.
DBCC CHECKIDENT ('TableName', RESEED, 1000000000);
Instead of setting the value to 1000000000, the constraint is created again, and set to the correct identity range value currently specified on the table in the publication.
It looks like the CHECKIDENT command forces the constraint to be updated somehow.
The above solution worked for me, but was actually my attempt at just dropping the constraints and setting the publisher and subscriber to use different identity ranges so they would be able to insert rows in the tables. Fortunately the CHECKIDENT seemed to refresh the constraint, something i originally expected the sp_adjustpublisheridentityrange stored procedure to do - except it did nothing.
I ran the above command on both the publisher and the subscriber.
To add a NOT NULL Column to a table with many records, a DEFAULT constraint needs to be applied. This constraint causes the entire ALTER TABLE command to take a long time to run if the table is very large. This is because:
Assumptions:
The DEFAULT constraint modifies existing records. This means that the db needs to increase the size of each record, which causes it to shift records on full data-pages to other data-pages and that takes time.
The DEFAULT update executes as an atomic transaction. This means that the transaction log will need to be grown so that a roll-back can be executed if necessary.
The transaction log keeps track of the entire record. Therefore, even though only a single field is modified, the space needed by the log will be based on the size of the entire record multiplied by the # of existing records. This means that adding a column to a table with small records will be faster than adding a column to a table with large records even if the total # of records are the same for both tables.
Possible solutions:
Suck it up and wait for the process to complete. Just make sure to set the timeout period to be very long. The problem with this is that it may take hours or days to do depending on the # of records.
Add the column but allow NULL. Afterward, run an UPDATE query to set the DEFAULT value for existing rows. Do not do UPDATE *. Update batches of records at a time or you'll end up with the same problem as solution #1. The problem with this approach is that you end up with a column that allows NULL when you know that this is an unnecessary option. I believe that there are some best practice documents out there that says that you should not have columns that allow NULL unless it's necessary.
Create a new table with the same schema. Add the column to that schema. Transfer the data over from the original table. Drop the original table and rename the new table. I'm not certain how this is any better than #1.
Questions:
Are my assumptions correct?
Are these my only solutions? If so, which one is the best? I f not, what else could I do?
I ran into this problem for my work also. And my solution is along #2.
Here are my steps (I am using SQL Server 2005):
1) Add the column to the table with a default value:
ALTER TABLE MyTable ADD MyColumn varchar(40) DEFAULT('')
2) Add a NOT NULL constraint with the NOCHECK option. The NOCHECK does not enforce on existing values:
ALTER TABLE MyTable WITH NOCHECK
ADD CONSTRAINT MyColumn_NOTNULL CHECK (MyColumn IS NOT NULL)
3) Update the values incrementally in table:
GO
UPDATE TOP(3000) MyTable SET MyColumn = '' WHERE MyColumn IS NULL
GO 1000
The update statement will only update maximum 3000 records. This allow to save a chunk of data at the time. I have to use "MyColumn IS NULL" because my table does not have a sequence primary key.
GO 1000 will execute the previous statement 1000 times. This will update 3 million records, if you need more just increase this number. It will continue to execute until SQL Server returns 0 records for the UPDATE statement.
Here's what I would try:
Do a full backup of the database.
Add the new column, allowing nulls - don't set a default.
Set SIMPLE recovery, which truncates the tran log as soon as each batch is committed.
The SQL is: ALTER DATABASE XXX SET RECOVERY SIMPLE
Run the update in batches as you discussed above, committing after each one.
Reset the new column to no longer allow nulls.
Go back to the normal FULL recovery.
The SQL is: ALTER DATABASE XXX SET RECOVERY FULL
Backup the database again.
The use of the SIMPLE recovery model doesn't stop logging, but it significantly reduces its impact. This is because the server discards the recovery information after every commit.
You could:
Start a transaction.
Grab a write lock on your original table so no one writes to it.
Create a shadow table with the new schema.
Transfer all the data from the original table.
execute sp_rename to rename the old table out.
execute sp_rename to rename the new table in.
Finally, you commit the transaction.
The advantage of this approach is that your readers will be able to access the table during the long process and that you can perform any kind of schema change in the background.
Just to update this with the latest information.
In SQL Server 2012 this can now be carried out as an online operation in the following circumstances
Enterprise Edition only
The default must be a runtime constant
For the second requirement examples might be a literal constant or a function such as GETDATE() that evaluates to the same value for all rows. A default of NEWID() would not qualify and would still end up updating all rows there and then.
For defaults that qualify SQL Server evaluates them and stores the result as the default value in the column metadata so this is independent of the default constraint which is created (which can even be dropped if no longer required). This is viewable in sys.system_internals_partition_columns. The value doesn't get written out to the rows until next time they happen to get updated.
More details about this here: online non-null with values column add in sql server 2012
Admitted that this is an old question. My colleague recently told me that he was able to do it in one single alter table statement on a table with 13.6M rows. It finished within a second in SQL Server 2012. I was able to confirm the same on a table with 8M rows. Something changed in later version of SQL Server?
Alter table mytable add mycolumn char(1) not null default('N');
I think this depends on the SQL flavor you are using, but what if you took option 2, but at the very end alter table table to not null with the default value?
Would it be fast, since it sees all the values are not null?
If you want the column in the same table, you'll just have to do it. Now, option 3 is potentially the best for this because you can still have the database "live" while this operation is going on. If you use option 1, the table is locked while the operation happens and then you're really stuck.
If you don't really care if the column is in the table, then I suppose a segmented approach is the next best. Though, I really try to avoid that (to the point that I don't do it) because then like Charles Bretana says, you'll have to make sure and find all the places that update/insert that table and modify those. Ugh!
I had a similar problem, and went for your option #2.
It takes 20 minutes this way, as opposed to 32 hours the other way!!! Huge difference, thanks for the tip.
I wrote a full blog entry about it, but here's the important sql:
Alter table MyTable
Add MyNewColumn char(10) null default '?';
go
update MyTable set MyNewColumn='?' where MyPrimaryKey between 0 and 1000000
go
update MyTable set MyNewColumn='?' where MyPrimaryKey between 1000000 and 2000000
go
update MyTable set MyNewColumn='?' where MyPrimaryKey between 2000000 and 3000000
go
..etc..
Alter table MyTable
Alter column MyNewColumn char(10) not null;
And the blog entry if you're interested:
http://splinter.com.au/adding-a-column-to-a-massive-sql-server-table
I had a similar problem and I went with modified #3 approach. In my case the database was in SIMPLE recovery mode and the table to which column was supposed to be added was not referenced by any FK constraints.
Instead of creating a new table with the same schema and copying contents of original table, I used SELECT…INTO syntax.
According to Microsoft (http://technet.microsoft.com/en-us/library/ms188029(v=sql.105).aspx)
The amount of logging for SELECT...INTO depends on the recovery model
in effect for the database. Under the simple recovery model or
bulk-logged recovery model, bulk operations are minimally logged. With
minimal logging, using the SELECT… INTO statement can be more
efficient than creating a table and then populating the table with an
INSERT statement. For more information, see Operations That Can Be
Minimally Logged.
The sequence of steps :
1.Move data from old table to new while adding new column with default
SELECT table.*, cast (‘default’ as nvarchar(256)) new_column
INTO table_copy
FROM table
2.Drop old table
DROP TABLE table
3.Rename newly created table
EXEC sp_rename 'table_copy', ‘table’
4.Create necessary constraints and indexes on the new table
In my case the table had more than 100 million rows and this approach completed faster than approach #2 and log space growth was minimal.
1) Add the column to the table with a default value:
ALTER TABLE MyTable ADD MyColumn int default 0
2) Update the values incrementally in the table (same effect as accepted answer). Adjust the number of records being updated to your environment, to avoid blocking other users/processes.
declare #rowcount int = 1
while (#rowcount > 0)
begin
UPDATE TOP(10000) MyTable SET MyColumn = 0 WHERE MyColumn IS NULL
set #rowcount = ##ROWCOUNT
end
3) Alter the column definition to require not null. Run the following at a moment when the table is not in use (or schedule a few minutes of downtime). I have successfully used this for tables with millions of records.
ALTER TABLE MyTable ALTER COLUMN MyColumn int NOT NULL
I would use CURSOR instead of UPDATE. Cursor will update all matching records in batch, record by record -- it takes time but not locks table.
If you want to avoid locks use WAIT.
Also I am not sure, that DEFAULT constrain changes existing rows.
Probably NOT NULL constrain use together with DEFAULT causes case described by author.
If it changes add it in the end
So pseudocode will look like:
-- without NOT NULL constrain -- we will add it in the end
ALTER TABLE table ADD new_column INT DEFAULT 0
DECLARE fillNullColumn CURSOR LOCAL FAST_FORWARD
SELECT
key
FROM
table WITH (NOLOCK)
WHERE
new_column IS NULL
OPEN fillNullColumn
DECLARE
#key INT
FETCH NEXT FROM fillNullColumn INTO #key
WHILE ##FETCH_STATUS = 0 BEGIN
UPDATE
table WITH (ROWLOCK)
SET
new_column = 0 -- default value
WHERE
key = #key
WAIT 00:00:05 --wait 5 seconds, keep in mind it causes updating only 12 rows per minute
FETCH NEXT FROM fillNullColumn INTO #key
END
CLOSE fillNullColumn
DEALLOCATE fillNullColumn
ALTER TABLE table ALTER COLUMN new_column ADD CONSTRAIN xxx
I am sure that there are some syntax errors, but I hope that this
help to solve your problem.
Good luck!
Vertically segment the table. This means you will have two tables, with the same primary key, and exactly the same number of records... One will be the one you already have, the other will have just the key, and the new Non-Null column (with default value) .
Modify all Insert, Update, and delete code so they keep the two tables in synch... If you want you can create a view that "joins" the two tables together to create a single logical combination of the two that appears like a single table for client Select statements...