SQL Server缓存问题

Question

I am using Sql Server 2008 R2, vs 2008, C# on .Net 3.5 and SqlHelper.

A method, say, updateData(int id) loads some data related to "id", does lots of calculations and processing and recommits the data. There is a separate programme doThings(int id) which does a set of tasks, wherein each task manipulates data related to "id" and then commits that data within a transaction. Some of these tasks are calling updateData(int id) after they commit, however, updateData(int id) is not updating the data as per the latest commit. After a while if I rerun updateData(int id), then the update is completed as it should.

To make it more clear, here's what the program is doing-

doTask(int id) //updates some table related to id and calls updateData()
doTask(int id) //updates some table related to id and calls updateData()
doTask(int id) //updates some table related to id and calls updateData()
doTask(int id) //updates some table related to id and calls updateData()
...

Output - Data is not updated

After a while -

updateData() //recalculates and updates the data

Output - Data is updated

I know SQL Server caches query result sets. However, if I have updated a part of the table which is in cache then shouldn't it recreate the result set. I have tried this in different environments (testing and production) without much help.

Each of doTask(int id) is using Transactions to update the database and that transaction is completed sans which last call of updateData will not update the data as it did eventually. Once its transaction is completed, updateData() is called which also uses transactions . Is there anything related to caching that can help here? Because the amount of code that i will have to post here is tremendous and I am not even allowed to do that.

I tried 2 things and it worked in both the cases-

1. added a thread.sleep of 500ms
2. debugged and held off the call to updateData() in doTask() for just a second

Answer 1

I know SQL Server caches query result sets

This is incorrect. SQL Server does not cache query results, nor does any other relational database for the matter .

You need to provide a clear example of what the problem is, the table structure, the queries you run, the expected result and the actual result. As is, this question is unanswerable.

Based on your comment about result caching I'm not convinced you understand transactions and isolation. Assuming your code (which was not shown at all) at the very least does a query as opposed to showing again and again the same locally cached data, what you describe could be explained by lost updates (incorrect code in your app) and as well by operating under snapshot isolation and not understanding the behavior.

Answer 2

Sql server wont cache the results it caches the plan to generate the results. Can you put up what the query is that UpdateData calls? It seems maybe the transaction has begun but not committed? Or if you are running the same UpdateData(), it might be creating a lock like condition on the table preventing other instances from updating.