Database Access Synchronization in a Distributed Application

Question

The common bit of programming logic that I find in myself is often something like the following pseudocode:

Let X = some value
Let Database = some external Database handle

if !Database.contains(X):
   SomeCalculation()
   Database.insert(X)

However, in a multi-threaded program, we have a race condition. Thread A can check if it is Xin Database, find it, and then go to the call SomeCalculation(). Meanwhile, Thread B also checks if it is Xin Database, find it and do not insert a duplicate.

So, of course, this needs to be synchronized, for example:

Let X = some value
Let Database = some external Database handle

LockMutex()
if !Database.contains(X):
   SomeCalculation()
   Database.insert(X)
UnlockMutex()

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Answer 1

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Answer 2

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Answer 3

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Let X = some value
Let Database = some external Database handle

xResposible = Definer.defineResponsibleFor(X);

if(xResposible == me)
    if !Database.contains(X):
       SomeCalculation()
       Database.insert(X)

, defineResponsibleFor , . , X Definer, . , . , ( , Definer - ). anyawy...:)