Context: I have a system that acts as a Web UI for a legacy accounting system. This legacy system sends me a large text file, several times a day, so I can update a CONTRACT table in my database (the file can have new contracts, or just updated values for existing contracts). This table currently has around 2M rows and about 150 columns. I can't have downtime during these updates, since they happen during the day and there's usually about 40 logged users in any given time.
My system's users can't update the CONTRACT table, but they can insert records in tables that reference the CONTRACT table (Foreign Keys to the CONTRACT table's ID column).
To update my CONTRACT table I first load the text file into a staging table, using a bulk insert, and then I use a MERGE statement to create or update the rows, in batches of 100k records. And here's my problem - during the MERGE statement, because I'm using READ COMMITED SNAPSHOT isolation, the users can keep viewing the data, but they can't insert anything - the transactions will timeout because the CONTRACT table is locked.
Question: does anyone know of a way to quickly update this large amount of rows, while enforcing data integrity and without blocking inserts on referencing tables?
I've thought about a few workarounds, but I'm hoping there's a better way:
- Drop the foreign keys. - I'd like to enforce my data consistency, so this don't sound like a good solution.
- Decrease the batch size on the MERGE statement so that the transaction is fast enough not to cause timeouts on other transactions. - I have tried this, but the sync process becomes too slow; Has I mentioned above, I receive the update files frequently and it's vital that the updated data is available shortly after.
- Create an intermediate table, with a single CONTRACTID column and have other tables reference that table, instead of the CONTRACT table. This would allow me to update it much faster while keeping a decent integrity. - I guess it would work, but it sounds convoluted.
Update: I ended up dropping my foreign keys. Since the system has been in production for some time and the logs don't ever show foreign key constraint violations, I'm pretty sure no inconsistent data will be created. Thanks to everyone who commented.
