SERVER-78124: add query count in getPlanCache list, this can help us to get the hot query sql.

src/mongo/db/query/explain.cpp

@@ -376,6 +376,8 @@ void Explain::planCacheEntryToBSON(const PlanCacheEntry& entry, BSONObjBuilder*
     // Append whether or not the entry is active.
     out->append("isActive", entry.isActive);
     out->append("works", static_cast<long long>(entry.works));
+    // we can use this counter to get the highest frequency query sql in tht plancache
+    out->append("queryCount", static_cast<long long>(entry.queryCounters));
     out->append("timeOfCreation", entry.timeOfCreation);
 
     if (entry.debugInfo) {

src/mongo/db/query/get_executor.cpp

@@ -647,6 +647,9 @@ class PrepareExecutionHelper {
                                     "query"_attr = redact(_cq->toStringShort()));
                     }
 
+                    PlanCache* cache = CollectionQueryInfo::get(_collection).getPlanCache();
+                    cache->increaseCacheQueryCounters(*_cq);
+
                     return buildCachedPlan(
                         std::move(querySolution), plannerParams, cs->decisionWorks);
                 }

src/mongo/db/query/plan_cache.cpp

@@ -257,6 +257,7 @@ PlanCacheEntry::PlanCacheEntry(std::unique_ptr<const SolutionCacheData> plannerD
       planCacheKey(planCacheKey),
       isActive(isActive),
       works(works),
+      queryCounters(0),
       debugInfo(std::move(debugInfo)),
       estimatedEntrySizeBytes(_estimateObjectSizeInBytes()) {
     invariant(this->plannerData);
@@ -669,6 +670,20 @@ void PlanCache::deactivate(const CanonicalQuery& query) {
     entry->isActive = false;
 }
 
+//increase the query counters which hit the plan
+void PlanCache::increaseCacheQueryCounters(const CanonicalQuery& query) {
+    PlanCacheKey key = computeKey(query);
+    stdx::lock_guard<Latch> cacheLock(_cacheMutex);
+    PlanCacheEntry* entry = nullptr;
+    Status cacheStatus = _cache.get(key, &entry);
+    if (!cacheStatus.isOK()) {
+        invariant(cacheStatus == ErrorCodes::NoSuchKey);
+        return;
+    }
+    invariant(entry);
+    entry->queryCounters++;
+} 
+
 PlanCache::GetResult PlanCache::get(const CanonicalQuery& query) const {
     PlanCacheKey key = computeKey(query);
     return get(key);

src/mongo/db/query/plan_cache.h

@@ -401,6 +401,9 @@ class PlanCacheEntry {
     // cause this value to be increased.
     size_t works = 0;
 
+    //the query count that use this plan to run the sql
+    uint64_t queryCounters = 0;
+
     // Optional debug info containing detailed statistics. Includes a description of the query which
     // resulted in this plan cache's creation as well as runtime stats from the multi-planner trial
     // period that resulted in this cache entry.
@@ -519,6 +522,12 @@ class PlanCache {
      */
     void deactivate(const CanonicalQuery& query);
 
+    /**
+     * increase the query counters that hit this cached plan.
+     * through this counters, we can get the hot query
+     */
+    void increaseCacheQueryCounters(const CanonicalQuery& query);
+
     /**
      * Look up the cached data access for the provided 'query'.  Used by the query planner
      * to shortcut planning.