BPCheckNestedLoopinCode : Nested data access loop found in method

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Posted on by CU27040922-15

Hi guys,

I have this warning: Nested data access loop found in X method for this part (attached bellow), and I am not really sure how to get rid of it. Also I couldn't have find anything useful.

Could you please help me with that?

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Martin Dráb 240,288 Most Valuable Professional on at

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It warns your about a performance problem. Let's say your outer query returns five records and the inner one returns ten for each localX.xId. Then you'll run 5*10 more queries than necessary. This can easily cause a huge problem.

The fix of this bug is simple - use a join to fetch both table at once in a single query.

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Layan Jwei 8,282 Super User 2026 Season 2 on at

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Hi User,

As Martin said you need to replace the 2 whiles with a join -- for better performance
while select firstonly xId from localX order by y desc where localX.ItemId == table.Iteml join local where local.xId == localX.xId { }

Thanks,
Layan Jweihan

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Martin Dráb 240,288 Most Valuable Professional on at

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Only now I've noticed that the first loop uses firstOnly keyword, therefore there doesn't have to a be any loop at all. You can do something like this:
select firstonly xId from localX order by y desc where localX.ItemId == table.ItemId; if (localX.xId) { while select local where local.xId == localX.xId; { } }

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