concurrency control

[beniwal]

Hi,

OnSelect property of a button I am using the below formula:

UpdateContext({rID : First(SortByColumns('[dbo].[SN]',"RID",Descending)).RID+1});

Patch('[dbo].[SN]',Defaults('[dbo].[SN]'),
{
Note: HtmlText.HtmlText,
RID:rID
});

Note:- RID is not the primary key, it can be duplicated so I can't make it autoincremented.

My concern is when multiple users will click this button concurrently, will it create any issue?

Please guide, thanks in advance

[Pstork1]

It could cause a problem in the sense that you might end up with duplicate entries.  But the likelihood is low.  The amount of time required between your updatecontext and patch statements should be measured in seconds at most.  It depends on how many users will be using the system at any one time.

[RezaDorrani]

Hi @beniwal 

Why not directly calculate the rid in the patch statement, this would avoid that miniscule possibility of 2 users having duplicate rid's

It can still be a duplicate with the below approach, if both users click button at the same time

Patch('[dbo].[SN]',Defaults('[dbo].[SN]'),
{
Note: HtmlText.HtmlText,
RID:First(SortByColumns('[dbo].[SN]',"RID",Descending)).RID+1
});

Regards,

Reza Dorrani

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[beniwal]

Hi

@Pstork1  Thanks for your reply. Can you please suggest any solution to this problem?

@RezaDorrani Thanks, for your suggestion. However, I can't do that because I am using 'rID' variable later on for other tasks.

[RezaDorrani · Accepted solution]

Hi @beniwal 

Patch will return to you the context of the item updates

example:

Set(varTest, Patch(...))

varTest will have the context of the item you need

you can then get rid and set it in your variable

Regards,

Reza Dorrani

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[Pstork1]

There really is no solution to this problem. As I said the likelihood that you will have two users enter a record at exactly the same time is very small.  Its called optomistic concurrency.  The only real solution is to lock the database when a user is entering a record so that no one enters a duplicate or makes an update that will overwrite the existing record.  Just run a process every so often that scans for dupicate IDs and then resolve them either programmatically or manually.

[beniwal]

hi @RezaDorrani ,

Thank you so much for your help!

This is exactly what I need.

Can you please suggest anything for error handling. Lets say while inserting patch function through any error what to do in that case?

[RezaDorrani]

Hi @beniwal 

You can check the same variable to see if data has been patched successfully 

Check this post

https://powerusers.microsoft.com/t5/General-Discussion/Making-sure-a-patch-is-successful/td-p/124500

Regards,

Reza Dorrani

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