How to have a batch transaction?

[Sri]

I am inserting records into a table - around 1 million records. I want
to do the insert 10000 records at a time using TRAN. My insert
statement is very simple:
BEGIN TRAN T1
Insert INTO TABLE A
(ColA, ColB, ColC)
Select B.TBLBCOLA, B.TBLBCOLB, B.TBLBCOLC
FROM tbltable B
WHERE blah balh...etc.

COMMIT TRAN T1


Any hep or link on the syntax will be helpful!
Thanks
Sri

[Gary]

Re: How to have a batch transaction?

Why would you do this? Your insert..select statement is already atomic
and doesn't need a transaction. Besides, you're not checking for
errors and rolling back so it's useless.

[Sri]

Re: How to have a batch transaction?

I have to do this in batches because my log ran out of space in tempdb.

[Phil]

Re: How to have a batch transaction?

You can't do it inside a single transaction, because this won't free-up
any space in the tran log until the whole process has completed.

As Gary says, if you're splitting the insert into multiple batches,
there's no point in placing each one in iots own transaction because
it's atomic.

If you can delete the records from TableB after you've inserted into
TableA, then life is comparatively simple:


declare @counter int
declare @rows_affected int

set rowcount 10000

Insert INTO TABLE A
(ColA, ColB, ColC)
Select B.TBLBCOLA, B.TBLBCOLB, B.TBLBCOLC
FROM tbltable B
WHERE blah balh...etc

select @rows_affected = @@ROWCOUNT

delete Table B
WHERE blah balh...etc

while @rows_affected > 0
begin

Insert INTO TABLE A
(ColA, ColB, ColC)
Select B.TBLBCOLA, B.TBLBCOLB, B.TBLBCOLC
FROM tbltable B
WHERE blah balh...etc

select @rows_affected = @@ROWCOUNT

delete Table B
WHERE blah balh...etc

end

set rowcount 0


This will repeatedly insert 10000 records into table A, then delete the
same from Table B until there are no more records left that match the
WHERE clause. The final iteration of the loop will probably affect <
10000 records.

If you can't delete from tableB, you can use the same principle, but
will have to compare the PK values in TableA with the max equivalent
for those records just inserted into table B, something like:

(Assuming colA is the PK):

set rowcount 10000

Insert INTO TABLE A
(ColA, ColB, ColC)
Select B.TBLBCOLA, B.TBLBCOLB, B.TBLBCOLC
FROM tbltable B
WHERE blah balh...etc

while @@rowcount > 0
begin

select @max_A = max(colA) from TableA

Insert INTO TABLE A
(ColA, ColB, ColC)
Select B.TBLBCOLA, B.TBLBCOLB, B.TBLBCOLC
FROM tbltable B
WHERE blah balh...etc
and ColA > @max_A

end

[Gary]

Re: How to have a batch transaction?

Doing it in batches is fine, that's not what I was complaining about.
It's using the BEGIN TRAN..COMMIT TRAN, which you don't need unless
you're doing multiple commands and actually checking for errors.
Transactions should be implicit with atomic statements.

[Sri]

Re: How to have a batch transaction?

Rather...I thought a batch process might help since this log space ran
out comes up after I fire my query 2 hrs ago.

[Hugo Kornelis]

Re: How to have a batch transaction?

On 8 Feb 2005 09:34:02 -0800, Sri wrote:
[color=blue]
>I am inserting records into a table - around 1 million records. I want
>to do the insert 10000 records at a time using TRAN. My insert
>statement is very simple:
>BEGIN TRAN T1
>Insert INTO TABLE A
>(ColA, ColB, ColC)
>Select B.TBLBCOLA, B.TBLBCOLB, B.TBLBCOLC
>FROM tbltable B
>WHERE blah balh...etc.
>
>COMMIT TRAN T1
>
>
>Any hep or link on the syntax will be helpful![/color]

Hi Sri,

You'll need something like this generic format:

SET ROWCOUNT 10000
WHILE 1 = 1
BEGIN
INSERT INTO TableA (ColA, ColB, ColC)
SELECT b.ColA, b.ColB, b.ColC
FROM TableB AS b
LEFT JOIN TableA AS a
ON a.ColA = b.ColA
AND a.ColB = b.ColB
-- Replace the above with whichever column (or combination of columns)
-- suffices to uniquely identify exactly one row in the data.
WHERE a.ColA IS NULL
-- Use any column from table A that will never contain NULL
-- The left join with a test for NULL in a non NULLable column
-- is a trick; it has the same effect as a NOT EXISTS subquery,
-- but is often quicker
IF @@ROWCOUNT = 0 BREAK
BACKUP LOG MyDatabase
END
SET ROWCOUNT 0

The "backup log" is necessary - else, the logged events will still be kept
in the log. If you don't need recoverability during this operation (i.e.
it suffices to restore an old full or incremental backup and repeat the
mega insert process), you can also use BACKUP LOG MyDatebase WITH NO_LOG.
If your database is in the simple recovery model, you can omit this step.

If you used BACKUP LOG MyDatabase WITH NO_LOG, then you should take a full
or incremental database backup directly after this process is finished.

Best, Hugo
--

(Remove _NO_ and _SPAM_ to get my e-mail address)