Sql-server – How to limit a SQL stored procedure to be run by one person at a time

sql serversql-server-2012stored-procedurest-sql

I have a stored procedure that basically selects values from one table and inserts them to another, a sort of archiving. I want to avoid multiple people from doing that at the same time.

While this procedure is running, I don't want anyone else to be able to start it, however I don't want serialization, the other person to run the procedure after I am done with it.

What I want is for the other person trying to start it to get an error, while I am running the procedure.

I've tried with using sp_getapplock, however I can't manage to completely stop the person from running the procedure.

I also tried finding the procedure with sys.dm_exec_requests and blocking the procedure, while this does work, i think it's not optimal because on some servers I don't have the permissions to run sys.dm_exec_sql_text(sql_handle).

What is the best way for me to do this?

Best Answer

To add to @Tibor-Karaszi's answer, setting a lock timeout doesn't actually produce an error (I've submitted a PR against the docs). sp_getapplock just returns -1, so you have to check the return value. So like this:

create or alter procedure there_can_be_only_one 
as
begin
begin transaction

  declare @rv int
  exec @rv = sp_getapplock 'only_one','exclusive','Transaction',0
  if @rv < 0
   begin
      throw 50001, 'There is already an instance of this procedure running.', 10
   end

  --do stuff
  waitfor delay '00:00:20'


commit transaction
end

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Sql-server – launch a stored procedure and immediately return without waiting for it to finish

It looks like there are multiple ways to accomplish this, but I found the simplest way was Martin's suggestion of setting up the procedure in a SQL job, and starting it using the asynchronous sp_start_job command from my stored procedure.

EXEC msdb.dbo.sp_start_job @job_name='Run2ndStoredProcedure'

This only works for me because I don't need to specify any parameters for my stored procedure.

Other suggestions that may work depending on your situation are

Using the SQL Service Broker like Martin and Sebastian suggest. This is probably the best suggestion if you don't mind the complexity of setting it up and learning how it works.
Running the process asynchronously in the code that is responsible for executing the stored procedure, like Mr.Brownstone suggested.

Not a bad idea, however in my case the stored procedure gets called from multiple places, so finding all those places and ensuring they call the 2nd procedure too didn't seem that practical. Also, the 2nd stored procedure is fairly critical, and forgetting to run it could cause some major problems for our company.
Make the 1st procedure set a flag, and setup a recurring job to check for that flag and run if its set, like Jimbo suggested. I'm not a big fan of jobs that run constantly and check for changes every few minutes, but it certainly is an option worth considering depending on your situation.

PostgreSQL stored procedure which can return one of two custom rowtypes

Since your two types are composed from the same basic types in the same order, they are compatible with each other. So the return type will be the same for functions using them - if I understand correctly, your problem is you want to have the different names of the returned columns depending on the type.

This cannot be done from the database, but you can easily do it from your application. It can be done like (ugly pseudocode)

if type == 1 {
    execute("SELECT 1 AS id_normal_number, '00001' AS normal_number FROM your_function()")
} else {
    execute("SELECT 1 AS id_special_number, 'S0001' AS special_number FROM your_function()")
}

ie. changing only the names, but using the same DB function. Or you can invoke two different functions, this way you can avoid dynamic SQL, which may be desirable for readability/performance, depending on some circumstances.

Best Answer

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Sql-server – launch a stored procedure and immediately return without waiting for it to finish

PostgreSQL stored procedure which can return one of two custom rowtypes

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