[GitHub] [geode-native] mmartell commented on a change in pull request #830: GEODE-8891: Make static regex a Meyers Singleton in ThinClientRegion

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mmartell commented on a change in pull request #830:
URL: https://github.com/apache/geode-native/pull/830#discussion_r665755714



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File path: cppcache/src/ThinClientRegion.cpp
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@@ -589,7 +595,7 @@ std::shared_ptr<SelectResults> ThinClientRegion::query(
   }
 
   std::string squery;
-  if (std::regex_search(predicate, PREDICATE_IS_FULL_QUERY_REGEX)) {
+  if (std::regex_search(predicate, IsFullQueryRegex::instance())) {

Review comment:
       If initializing a constant something is relatively expensive (i.e., a significant cost relative to its use), I'd prefer to initialize it only once, so I can amortize the cost of initialization.
   
   In this case, I believe mreddington is advocating just declaring it locally inside of functions that use it, and not worry about the cost. Although calling the regex CTOR is likely a small percentage of the total test time, having to recreate a regex that's const seems silly.
   
   If you declare the regex as a const static inside the function that uses it, then it will be initialized only once when the function is first used, thereby solving any cost concern associated with a regex CTOR. Also, C++11 guarantees that dynamic initialization of function-local statics is thread-safe, in case two threads call the function using the local regex at the same time.
   
   So my recommendation is to simply move the original 2 lines of code inside the function that uses it.
   ```
   
   




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