SERVER-17364 Unify handling of child stages into PlanStage base class

This is prep for adding more methods that need to propagate to children.

1 files changed, 5 insertions, 29 deletions

diff --git a/src/mongo/db/exec/limit.cpp b/src/mongo/db/exec/limit.cpp
index 06566149cd8..a2c1d73b399 100644
--- a/src/mongo/db/exec/limit.cpp
+++ b/src/mongo/db/exec/limit.cpp
@@ -43,14 +43,15 @@ using stdx::make_unique;
 const char* LimitStage::kStageType = "LIMIT";
 
 LimitStage::LimitStage(long long limit, WorkingSet* ws, PlanStage* child)
-    : _ws(ws), _child(child), _numToReturn(limit), _commonStats(kStageType) {
+    : PlanStage(kStageType), _ws(ws), _numToReturn(limit) {
     _specificStats.limit = _numToReturn;
+    _children.emplace_back(child);
 }
 
 LimitStage::~LimitStage() {}
 
 bool LimitStage::isEOF() {
-    return (0 == _numToReturn) || _child->isEOF();
+    return (0 == _numToReturn) || child()->isEOF();
 }
 
 PlanStage::StageState LimitStage::work(WorkingSetID* out) {
@@ -65,7 +66,7 @@ PlanStage::StageState LimitStage::work(WorkingSetID* out) {
     }
 
     WorkingSetID id = WorkingSet::INVALID_ID;
-    StageState status = _child->work(&id);
+    StageState status = child()->work(&id);
 
     if (PlanStage::ADVANCED == status) {
         *out = id;
@@ -94,39 +95,14 @@ PlanStage::StageState LimitStage::work(WorkingSetID* out) {
     return status;
 }
 
-void LimitStage::saveState() {
-    ++_commonStats.yields;
-    _child->saveState();
-}
-
-void LimitStage::restoreState(OperationContext* opCtx) {
-    ++_commonStats.unyields;
-    _child->restoreState(opCtx);
-}
-
-void LimitStage::invalidate(OperationContext* txn, const RecordId& dl, InvalidationType type) {
-    ++_commonStats.invalidates;
-    _child->invalidate(txn, dl, type);
-}
-
-vector<PlanStage*> LimitStage::getChildren() const {
-    vector<PlanStage*> children;
-    children.push_back(_child.get());
-    return children;
-}
-
 unique_ptr<PlanStageStats> LimitStage::getStats() {
     _commonStats.isEOF = isEOF();
     unique_ptr<PlanStageStats> ret = make_unique<PlanStageStats>(_commonStats, STAGE_LIMIT);
     ret->specific = make_unique<LimitStats>(_specificStats);
-    ret->children.push_back(_child->getStats().release());
+    ret->children.push_back(child()->getStats().release());
     return ret;
 }
 
-const CommonStats* LimitStage::getCommonStats() const {
-    return &_commonStats;
-}
-
 const SpecificStats* LimitStage::getSpecificStats() const {
     return &_specificStats;
 }