We have a production table with 770 million rows and change. We want(/need?) to change the Primary ID column from int to bigint to allow for future growth (and to avoid the sudden stop when the 32bit integer space is exhausted)
Experiments in DEV have shown that this is not as simple as altering the column as we would need to drop the index and then re-create it. So far in DEV (which is a bit humbler than PROD) the dropping of the index has not finished after 1 and a half hours. This table is hit 24/7 and having it offline for such a long time is not an option.
Has anyone else had to deal with a similar situation? How did you get it done?
Are there alternatives?
Edit: Additional Info:
The Primary key is clustered.
You could attempt a staged approach.
Create a new bigint column
Create an insert trigger to keep new entries in sync with the 2 columns
Execute an update to populate all the empty values in the bigint column with the converted value
Change the primary index on the table from your old id column to the new one
Point any FK's and queries to use the new column
Change the new column to become your identity column and remove the insert trigger from #2
Delete the old ID column
You should end up spreading the pain out over these 7 steps instead of hitting it all at once.
Create a parallel table with the longer data type for new rows and UNION the results?
What I had to do was copy the data into a new table with the desired structure (primary/clustered key only, non-clustered/FK once complete). If you don't have the room, you could bcp out the data and back in. You may need an application outage to make this happen.
What doesn't work: alter table Orderhistory alter column ID bigint because of the primary key. Don't drop the key and alter column as you will just fill your log file and take much longer than copy/bcp.
Never use the SSMS tools designer to change a column property, it copies table into temp table then does a rename once done. Lookup the alter table alter column syntax and use it and possibly defrag once complete if you modified a column wider that sits in middle of table.
Related
I need to add a new column and make it the primary key in SQL Server; the table in question does not yet have a unique key column.
Here is the sample table http://www.sqlfiddle.com/#!18/8a161/1/0
My goal is simply to have a column ID and insert values from 1 to 1160 (total number of records in this table) and make that the primary key. Also is there a way to automatically add the numbers from 1-1160 without adding each record one by one since there are 1000+ rows in this table?
Thank you!
Simply alter the table and add the column with the appropriate characteristics.
alter table x add id smallint identity(1,1) not null primary key;
Thrown together quickly and you probably should get in the habit of naming constraints. fiddle. I will note that you may or may not want to use an identity column - think carefully about your actual goal and how you want to continue using this table after the alteration.
Is it possible to only alter a table to make an existing column a serial auto generated key, without adding a new column? Sorry if this question is a bit newbie-ish for PostgreSQL, I'm more a SQL Server person but moving to PostgreSQL..
In a nut shell the program will copying an existing SQL Server database into PostgreSQL. With the desire to have a mirrored DB in PostgreSQL as the source from SQL Server with the only caveat one may selectively include/exclude any table or column as desired, or do everything...
Given the process copies all values, thought one should be able create the keys after the copy has finished just as one may do in SQL Server. Thought PostgreSQL would have a comparable methods as SQL Server's SET INSERT_IDENTITY [ON|OFF] so one may override the auto generated key with a desired value. Not seeing an equivalent in PostgreSQL. So my fallback is to create the mirrored records in Postgres without keys any keys and then alter the tables. But it seems to fix up the table as desired one has create a new column, but doing this break or cause a headache fixing up the RI for PK/FK relationships.
Any suggestions? Thanks in advance.
In PostgreSQL, the auto-generated key is always overridden if you insert an explicit value for it. If you don't specify a value (omit the column), or specify the keyword DEFAULT, a generated key is used.
Given table
CREATE TABLE t1 (id serial primary key, dat text);
then both these will get a generated key from sequence t1_id_seq:
INSERT INTO t1 (dat) VALUES ('fred');
INSERT INTO t1 (id, dat) VALUES (DEFAULT, 'bob');
This will instead provide its own value:
INSERT INTO t1 (id, dat) VALUES (42, 'joe');
You are responsible for ensuring that the provided value doesn't conflict with existing data, or with future values the identity sequence will generate. PostgreSQL will not notice that you manually inserted a row with id 42 and skip when its own sequence counter gets to that point.
Usually what you do is load with provided values, then reset the sequence to the max of all keys already in the table, so it keeps counting from there for new local inserts.
I have a script for microsoft sql server database which has hundreds of tables and tables contains data as well. This is the database of a web application.what I want to do is to delete the previous records and reset the primary key to 1 or 0.
I have tried
`DBCC CHECKIDENT ('dbo.tbl',RESEED,0); `
but it does not work for me as in most of the tables the primary key is not identity.
I can not truncate the table as its primary key is being used as FK in many other tables.
I have also tried to add the identity specification in the primary key of the table and run the checkident query and then changing it back to non-identity spec, but after adding the record again it starts from where it left.
Making changes in the code is not an option for me.
please help.
According with your question I am not sure about the main objective, Why? If you need truncate a lot of tables and change their structures to have an Identity property why you can't disabled the FK? . In the past I have used an standard process for rebuild a table and migrate all the information, this represent a group of steps, I would try to help you but you should follow the next steps.
Steps:
1) Disable FK for alter the structure of your tables. You can get the solution for this task in the next link:
Temporarily disable all foreign key constraints
2) Alter the table with the new property Identity, this is a classic process of ALTER TABLE xxxxxx.
3) Execute the syntax that previously posted :
DBCC CHECKIDENT ('dbo.tbl',RESEED,0);
Try to follow this path and if you have any problem only ask us.
You can not truncate table that have relation. You shoud remove relation firstly.
My understanding of this question:
You have a database with tables that you want to empty and next have them use primary key values starting at 0 or 1.
Some of these tables use an identity value and you already have a solution for those (you know you can find out which columns have an identity by using the sys.columns view? Look for the is_identity column).
Some tables do not use an identity but get their pk values from an unknown source, which we can't modify.
The only solution I see, is creating an after insert trigger (or modifying) on those tables that subtracts from the new pk value.
E.g.: your "hidden generator" will generate a next value 5254, but you want the next pk value to become one:
CREATE TRIGGER trg_sometable_ai
ON sometable
AFTER INSERT
AS
BEGIN
UPDATE st
SET st.pk_col = st.pk_col - 5253
FROM sometable AS st
INNER JOIN INSERTED AS i
ON i.pk_col = th.pk_col
END
You'll have to determine the next value and thus the "subtract value" for each table.
If the code also inserts child records into tables with a foreign key to this table, and uses the previously generated value, you have to modify those triggers as well...
This is a "last resort" solution and something I would recommend against in any scenario that has other options. Manipulating primary key values is generally not a good idea.
I have a table filled with data and one of the columns - TrackingNumber - is an integer value. I have gotten a request to change it to auto-increment and to have it start the identity seed at 1000000. I know that I cannot alter a column to be an identity column in an existing table with data, so I have two options: either create an entirely new table and then move data from the old table into that new table or add an new identity column and update it with data from the old column.
The problem is that I need to retain all the existing values in column TrackingNumber. I have tried the following:
1) ALTER TABLE [dbo].[Table1]
ADD [TrackingNumber2] [bigint] IDENTITY (1000000, 1) NOT NULL
2) UPDATE [dbo].[Table1]
SET [TrackingNumber2]=[TrackingNumber]
3) ALTER TABLE [dbo].[Table1]
DROP COLUMN [TrackingNumber]
GO
4) EXEC sp_rename 'Table1.TrackingNumber2', 'TrackingNumber','COLUMN'
I got an error on step 2 - Updating new column with the value from the old column: "Cannot update identity column 'TrackingNumber2'"
Can anyone recommend a workaround?
You just need to set identity_insert on for this table so you can update the values. Make sure you turn it back off when you complete the update. :)
https://msdn.microsoft.com/en-us/library/ms188059.aspx
Are you sure you need to use an identity column? There are alternatives. For example, since SQL Server 2012 (and azure, too), there are these things called sequences. You can define a sequence to start at any number you like:
create sequence dbo.TrackingSequence
as int
start with 1000000
increment by 1
no maxvalue
no cycle
no cache
Then, you can alter the table such that the default value for the column in question defaults from the sequence:
alter table dbo.MyTable
add constraint [MyTable.TrackingNumber.Default.TrackingSequence]
default( next value for dbo.TrackingSequence ) for TrackingNumber
(If the column already has a default value, you need to remove that first - in a separate statement.)
A sequence works a lot like an identity, but you don't have to disrupt existing values or the column definition per se.
The only trick is to remember to not specify the value for TrackingNumber, and let the DB do its thing.
Sequences are cool in that you can have one sequence that is used by multiple tables, giving you somewhat shorter db-wide unique IDs than alternatives in the past. For such an application, you'd probably be better off with a bigint column - or know that the tables in question aren't going to be terribly long.
I ended up creating a new table and moving data in there
I am trying to change a primary key Id to identity to increment 1 on each entry. But the column has been referenced already by other tables. Is there any way to set primary key to auto increment without dropping the foreign keys from other tables?
If the table isn't that large generate script to create an identical table but change the schema it created to:
CREATE TABLE MYTABLE_NEW (
PK INT PRIMARY KEY IDENTITY(1,1),
COL1 TYPEx,
COL2 TYPEx,
COLn
...)
Set your database to single-user mode or make sure no one is in the
database or tables you're changing or change the table you need to
change to READ/ONLY.
Import your data into MYTABLE_NEW from MYTABLE using set IDENTITY_INSERT on
Script your foreign key constraints and save them--in case you need
to back out of your change later and/or re-implement them.
Drop all the constraints from MYTABLE
Rename MYTABLE to MYTABLE_SAV
Rename MYTABLE_NEW to MYTABLE
Run constraint scripts to re-implement constraints on MYTABLE
p.s.
you did ask if there was a way to not drop the foreign key constraints. Here's something to try on your test system. on Step 4 run
ALTER TABLE MYTABLE NOCHECK CONSTRAINT ALL
and on Step 7 ALTER TABLE MYTABLE CHECK CONSTRAINT ALL. I've not tried this myself -- interesting to see if this would actually work on renamed tables.
You can script all this ahead of time on a test SQL Server or even a copy of the database staged on a production server--to make implementation day a no-brainer and gauge your SLAs for any change control procedures for your company.
You can do a similar methodology by deleting the primary key and re-adding it back, but you'll need to have the same data inserted in the new column before you delete the old column. So you'll be deleting and inserting schema and inserting primary key data with this approach. I like to avoid touching a production table if at all possible and having MYTABLE_SAV around in case "anything" unexpected occurs is a comfort to me personally--as I can tell management "the production data was not touched". But some tables are simply too large for this approach to be worthwhile and, also, tastes and methodologies differ largely from DBA to DBA.