How big is a SQL Server Delete query?
We ran a delete query on a database with 1.8bn rows. This delete would delete 1.2bn rows. In hindsight, we would have broken up this query into 100m at a time but we are in a position where it has been running for 24 hours and the log file is at 2Tb which appears to be the maximum size allowed for a log file.
What to do when SQL Server deletes a row?
This can be done by using “snapshot isolation” which was introduced with SQL Server 2005: If you have anything with cascading deletes make sure they are indexed. Highlighting the DELETE query and clicking Display estimated execution plan will show suggested indexes – which in my case included some cascading deletes.
How to delete top of table in SQL Server?
DECLARE @RowCount int WHILE 1=1 BEGIN DELETE TOP (10000) t1 FROM table t1 INNER JOIN table2 t2 ON t2.PrimaryKey = t1.PrimaryKey WHERE t1.YearProcessed <= 2007 SET @RowCount = @@ROWCOUNT IF (@RowCount < 10000) BREAK END This table is HIGHLY used.
Why is the DELETE statement hanging on SQL Server?
As SQL Server uses the Primary Key as a pointer in every index, any change to the primary index requires updating every index. Though, unless we are talking a high number, this shouldn’t be an issue.
Why is my delete query taking too much time?
You could be blocked by another session (most likely). Before you delete you should make sure noone else is locking the rows, eg: issue SELECT NULL FROM tablename WHERE colname=:value FOR UPDATE NOWAIT,
How long does it take to execute delete statement in SQL?
After a quick inspection all statements (SELECT, UPDATE, DELETE etc.) on the table ImportBarcodes that had only 1 row, took about 2 minutes to execute. Extended Events showed a whole lot PAGEIOLATCH_EX wait notifications. No indexes were present of the table and no triggers were registered.
When is a delete query useless in SQL?
If your table has one million rows and that value hits one hundred and fifty thousand of them then your index is useless. In fact it may be worse than useless if it is actually being used. Remember, a DELETE is a like a SELECT statement: we can tune its access path.