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What are the challenges of SQL BULK INSERT?
One of the challenges we face when using SQL bulk insert from files flat can be concurrency and performance challenges, especially if the load involves a multi-step data flow, where we can’t execute a latter step until we finish with an early step.
Why are inserts so slow in SQL Server?
If you don’t wrap sets of INSERTs into explicitly managed transaction then each INSERT is its own auto-committed transaction. Meaning each INSERT issues automatically a commit, and a commit has to wait until the log is durable (ie. written to disk). Flushing the log after each insert is extremely slow.
Why does SQL Server insert into large table take so long?
Recently I have experimented with changing the clustered index of the large table to an identity int column, which has brought the insert down from 3 hours to one hour, but I am still puzzled why this simple query should take so long to run (regardless of the size of the table) CREATE TABLE [dbo].
How big is a table in SQL Server?
I have a large table in a SQl Server 2008 database, it has about 570 million records. Every day we run a batch job that takes a file of 200,000 or so transaction records, does a group by and sum against this data and inserts it into the large table.
What’s the idea of the slow performing query?
The slow performing query is below. The idea is to INSERT records that aren’t there and later to UPDATE them as we calculate various bits of data. A prior step in the process has identified the items that need to be updated, done some calculations, and stuffed the results into the tempdb table Update_Item_Work.
How often does the companywide Inventory table update?
We have a process that takes data from stores and updates a company-wide inventory table. This table has rows for every store by date and by item. At customers with many stores, this table can get very large– on the order of 500 million rows. This inventory update process typically gets run many times a day as the stores enter data.
What are the rules for transactional behavior in PostgreSQL?
Some PostgreSQL data types and functions have special rules regarding transactional behavior. In particular, changes made to a sequence (and therefore the counter of a column declared using serial) are immediately visible to all other transactions and are not rolled back if the transaction that made the changes aborts.
How to set transaction isolation level in PostgreSQL?
Stricter behavior is permitted by the SQL standard: the four isolation levels only define which phenomena must not happen, not which phenomena must happen. The behavior of the available isolation levels is detailed in the following subsections. To set the transaction isolation level of a transaction, use the command SET TRANSACTION.
When to roll back a SQL BULK INSERT?
Identical to other CRUD operations, bulk loads, including SQL Bulk Insert, can be wrapped in a transaction and rolled back entirely if we don’t get our expected results, or if we experience a failure.
What happens when the Bulk insert errorfile fails?
So now I’m looking into the files created by the bulk insert errorfile switch, e.g. When there’s bad data, the bulk insert fails and (as per BOL) creates two files: and the CATCH block runs and I can do cool stuff. Fine and good.
Can you skip rows with Bulk insert / BCP?
I don’t think you can skip rows in a different format with BULK INSERT / BCP. It looks like it requires the ‘|’ even in the header data, because it reads up to that into the first column – swallowing up a newline into the first column. Obviously if you include a field terminator parameter, it expects that every row MUST have one.
When to remove indexes in SQL BULK INSERT?
Removing indexes prior to large inserts on a table, including when using SQL Bulk Insert, may be a best practice to increase performance. Are there scenarios that might change this practice of removing indexes prior to inserting a large amount of data?