SERVER-35980 Delete PlanCacheEntryFeedback.

This type was only used to house the score of the plan and
thus was not needed. We are removing it in advance of
planned format changes for the planCacheListPlans command.

4 files changed, 13 insertions, 44 deletions

diff --git a/src/mongo/db/commands/plan_cache_commands.cpp b/src/mongo/db/commands/plan_cache_commands.cpp
index 1210588d066..3c1d6a00a6a 100644
--- a/src/mongo/db/commands/plan_cache_commands.cpp
+++ b/src/mongo/db/commands/plan_cache_commands.cpp
@@ -425,7 +425,7 @@ Status PlanCacheListPlans::list(OperationContext* opCtx,
             BSONArrayBuilder scoresBob(feedbackBob.subarrayStart("scores"));
             for (size_t i = 0; i < entry->feedback.size(); ++i) {
                 BSONObjBuilder scoreBob(scoresBob.subobjStart());
-                scoreBob.append("score", entry->feedback[i]->score);
+                scoreBob.append("score", entry->feedback[i]);
             }
             scoresBob.doneFast();
         }
diff --git a/src/mongo/db/exec/cached_plan.cpp b/src/mongo/db/exec/cached_plan.cpp
index 33a9759f9a8..ef3bc771b64 100644
--- a/src/mongo/db/exec/cached_plan.cpp
+++ b/src/mongo/db/exec/cached_plan.cpp
@@ -322,12 +322,10 @@ const SpecificStats* CachedPlanStage::getSpecificStats() const {
 }
 
 void CachedPlanStage::updatePlanCache() {
-    std::unique_ptr<PlanCacheEntryFeedback> feedback = stdx::make_unique<PlanCacheEntryFeedback>();
-    feedback->stats = getStats();
-    feedback->score = PlanRanker::scoreTree(feedback->stats->children[0].get());
+    const double score = PlanRanker::scoreTree(getStats()->children[0].get());
 
     PlanCache* cache = _collection->infoCache()->getPlanCache();
-    Status fbs = cache->feedback(*_canonicalQuery, feedback.release());
+    Status fbs = cache->feedback(*_canonicalQuery, score);
     if (!fbs.isOK()) {
         LOG(5) << _canonicalQuery->ns() << ": Failed to update cache with feedback: " << redact(fbs)
                << " - "
diff --git a/src/mongo/db/query/plan_cache.cpp b/src/mongo/db/query/plan_cache.cpp
index f132dc077b9..ac5015b08d1 100644
--- a/src/mongo/db/query/plan_cache.cpp
+++ b/src/mongo/db/query/plan_cache.cpp
@@ -411,9 +411,6 @@ PlanCacheEntry::PlanCacheEntry(const std::vector<QuerySolution*>& solutions,
 }
 
 PlanCacheEntry::~PlanCacheEntry() {
-    for (size_t i = 0; i < feedback.size(); ++i) {
-        delete feedback[i];
-    }
     for (size_t i = 0; i < plannerData.size(); ++i) {
         delete plannerData[i];
     }
@@ -439,12 +436,8 @@ PlanCacheEntry* PlanCacheEntry::clone() const {
     entry->works = works;
 
     // Copy performance stats.
-    for (size_t i = 0; i < feedback.size(); ++i) {
-        PlanCacheEntryFeedback* fb = new PlanCacheEntryFeedback();
-        fb->stats.reset(feedback[i]->stats->clone());
-        fb->score = feedback[i]->score;
-        entry->feedback.push_back(fb);
-    }
+    entry->feedback = feedback;
+
     return entry;
 }
 
@@ -923,11 +916,7 @@ PlanCache::GetResult PlanCache::get(const PlanCacheKey& key) const {
     return {state, stdx::make_unique<CachedSolution>(key, *entry)};
 }
 
-Status PlanCache::feedback(const CanonicalQuery& cq, PlanCacheEntryFeedback* feedback) {
-    if (NULL == feedback) {
-        return Status(ErrorCodes::BadValue, "feedback is NULL");
-    }
-    std::unique_ptr<PlanCacheEntryFeedback> autoFeedback(feedback);
+Status PlanCache::feedback(const CanonicalQuery& cq, double score) {
     PlanCacheKey ck = computeKey(cq);
 
     stdx::lock_guard<stdx::mutex> cacheLock(_cacheMutex);
@@ -940,7 +929,7 @@ Status PlanCache::feedback(const CanonicalQuery& cq, PlanCacheEntryFeedback* fee
 
     // We store up to a constant number of feedback entries.
     if (entry->feedback.size() < static_cast<size_t>(internalQueryCacheFeedbacksStored.load())) {
-        entry->feedback.push_back(autoFeedback.release());
+        entry->feedback.push_back(score);
     }
 
     return Status::OK();
diff --git a/src/mongo/db/query/plan_cache.h b/src/mongo/db/query/plan_cache.h
index b0b767c13ea..159b724df04 100644
--- a/src/mongo/db/query/plan_cache.h
+++ b/src/mongo/db/query/plan_cache.h
@@ -50,22 +50,6 @@ struct QuerySolution;
 struct QuerySolutionNode;
 
 /**
- * When the CachedPlanStage runs a cached query, it can provide feedback to the cache.  This
- * feedback is available to anyone who retrieves that query in the future.
- */
-struct PlanCacheEntryFeedback {
-    // How well did the cached plan perform?
-    std::unique_ptr<PlanStageStats> stats;
-
-    // The "goodness" score produced by the plan ranker
-    // corresponding to 'stats'.
-    double score;
-};
-
-// TODO: Replace with opaque type.
-typedef std::string PlanID;
-
-/**
  * A PlanCacheIndexTree is the meaty component of the data
  * stored in SolutionCacheData. It is a tree structure with
  * index tags that indicates to the access planner which indices
@@ -283,9 +267,8 @@ public:
     // the other plans lost.
     std::unique_ptr<PlanRankingDecision> decision;
 
-    // Annotations from cached runs.  The CachedPlanStage provides these stats about its
-    // runs when they complete.
-    std::vector<PlanCacheEntryFeedback*> feedback;
+    // Scores from uses of this cache entry.
+    std::vector<double> feedback;
 
     // Whether or not the cache entry is active. Inactive cache entries should not be used for
     // planning.
@@ -407,10 +390,9 @@ public:
 
     /**
      * When the CachedPlanStage runs a plan out of the cache, we want to record data about the
-     * plan's performance.  The CachedPlanStage calls feedback(...) after executing the cached
-     * plan for a trial period in order to do this.
-     *
-     * Cache takes ownership of 'feedback'.
+     * plan's performance. The CachedPlanStage calls feedback(...) after executing the cached
+     * plan for a trial period in order to do this. Currently, the only feedback metric recorded is
+     * the score associated with the cached plan trial period.
      *
      * If the entry corresponding to 'cq' isn't in the cache anymore, the feedback is ignored
      * and an error Status is returned.
@@ -418,7 +400,7 @@ public:
      * If the entry corresponding to 'cq' still exists, 'feedback' is added to the run
      * statistics about the plan.  Status::OK() is returned.
      */
-    Status feedback(const CanonicalQuery& cq, PlanCacheEntryFeedback* feedback);
+    Status feedback(const CanonicalQuery& cq, double score);
 
     /**
      * Remove the entry corresponding to 'ck' from the cache.  Returns Status::OK() if the plan