Add comments.

src/graph/planner/match/ArgumentFinder.h

@@ -9,6 +9,8 @@
 
 namespace nebula {
 namespace graph {
+// ArgumentFinder find if a pattern use a named alias that already declared
+// in former patterns.
 class ArgumentFinder final : public StartVidFinder {
  public:
   static std::unique_ptr<ArgumentFinder> make() {

src/graph/planner/match/LabelIndexSeek.h

@@ -11,10 +11,8 @@
 namespace nebula {
 namespace graph {
 
-/*
- * The LabelIndexSeek was designed to find if could get the starting vids by tag
- * index.
- */
+// The LabelIndexSeek was designed to find if could get the starting vids by tag
+// index.
 class LabelIndexSeek final : public StartVidFinder {
  public:
   static std::unique_ptr<LabelIndexSeek> make() {

src/graph/planner/match/MatchClausePlanner.h

@@ -10,9 +10,7 @@
 
 namespace nebula {
 namespace graph {
-/*
- * The MatchClausePlanner was designed to generate plan for match clause;
- */
+// The MatchClausePlanner generates plan for match clause;
 class MatchClausePlanner final : public CypherClausePlanner {
  public:
   MatchClausePlanner() = default;
@@ -62,10 +60,8 @@ class MatchClausePlanner final : public CypherClausePlanner {
                         size_t startIndex,
                         SubPlan& subplan);
 
-  /*
-   * Project all named alias.
-   * TODO: Might not neccessary
-   */
+  // Project all named alias.
+  // TODO: Might not neccessary
   Status projectColumnsBySymbols(MatchClauseContext* matchClauseCtx, SubPlan& plan);
 
   YieldColumn* buildVertexColumn(MatchClauseContext* matchClauseCtx,

src/graph/planner/match/MatchPlanner.h

@@ -11,6 +11,7 @@
 
 namespace nebula {
 namespace graph {
+// MatchPlanner generate plans for Match statement based on AstContext.
 class MatchPlanner final : public Planner {
  public:
   static std::unique_ptr<MatchPlanner> make() {

src/graph/planner/match/OrderByClausePlanner.h

@@ -10,9 +10,7 @@
 
 namespace nebula {
 namespace graph {
-/*
- * The OrderByClausePlanner was designed to generate plan for order by clause;
- */
+// The OrderByClausePlanner generate plan for order by clause;
 class OrderByClausePlanner final : public CypherClausePlanner {
  public:
   OrderByClausePlanner() = default;

src/graph/planner/match/PaginationPlanner.h

@@ -10,9 +10,7 @@
 
 namespace nebula {
 namespace graph {
-/*
- * The PaginationPlanner was designed to generate subplan for skip/limit clause.
- */
+// The PaginationPlanner generate subplan for skip/limit clause.
 class PaginationPlanner final : public CypherClausePlanner {
  public:
   PaginationPlanner() = default;

src/graph/planner/match/PropIndexSeek.h

@@ -10,10 +10,8 @@
 
 namespace nebula {
 namespace graph {
-/*
- * The PropIndexSeek was designed to find if could get starting vids by tag
- * props or edge props index.
- */
+// The PropIndexSeek find if a plan could get starting vids by tag
+// props or edge props index.
 class PropIndexSeek final : public StartVidFinder {
  public:
   static std::unique_ptr<PropIndexSeek> make() {

src/graph/planner/match/ReturnClausePlanner.h

@@ -10,9 +10,7 @@
 
 namespace nebula {
 namespace graph {
-/*
- * The ReturnClausePlanner was designed to generated plan for return clause.
- */
+// The ReturnClausePlanner generate plan for return clause.
 class ReturnClausePlanner final : public CypherClausePlanner {
  public:
   ReturnClausePlanner() = default;

src/graph/planner/match/ScanSeek.h

@@ -10,10 +10,8 @@
 
 namespace nebula {
 namespace graph {
-/*
- * The ScanSeek was designed to find if could get the starting vids in
- * filter.
- */
+// The ScanSeek find if a plan could get the starting vids in
+// filter.
 class ScanSeek final : public StartVidFinder {
  public:
   static std::unique_ptr<ScanSeek> make() {

src/graph/planner/match/SegmentsConnector.h

@@ -13,10 +13,7 @@
 
 namespace nebula {
 namespace graph {
-/**
- * The SegmentsConnector was designed to be a util to help connecting the
- * plan segment.
- */
+// The SegmentsConnector is a util to help connecting the plan segment.
 class SegmentsConnector final {
  public:
   SegmentsConnector() = delete;

src/graph/planner/match/StartVidFinder.h

@@ -15,6 +15,27 @@ class StartVidFinder;
 
 using StartVidFinderInstantiateFunc = std::function<std::unique_ptr<StartVidFinder>()>;
 
+// A StartVidFinder find a generally good solution for traversing from the vids.
+// Currently we have five StartVidFinders:
+// 1. VertexIdSeek find if a plan could traverse from a given vid.
+// MATCH(n) WHERE id(n) = value RETURN n
+//
+// 2. ArgumentFinder find if a plan could traverse from some vids that already
+// beed traversed.
+// MATCH (n)-[]-(l), (l)-[]-(m) return n,l,m
+// MATCH (n)-[]-(l) MATCH (l)-[]-(m) return n,l,m
+//
+// 3. PropIndexSeek find if a plan could traverse from some vids that could be
+// read from the property indices.
+// MATCH(n:Tag{prop:value}) RETURN n
+// MATCH(n:Tag) WHERE n.prop = value RETURN n
+//
+// 4. LabelIndexSeek find if a plan could traverse from some vids that could be
+// read from the label indices.
+// MATCH(n: tag) RETURN n
+// MATCH(s)-[:edge]->(e) RETURN e
+//
+// 5. ScanSeek find if a plan could traverse from some vids by scanning.
 class StartVidFinder {
  public:
   virtual ~StartVidFinder() = default;
@@ -26,8 +47,12 @@ class StartVidFinder {
 
   bool match(PatternContext* patternCtx);
 
+  // The derived class should implement matchNode if the finder has
+  // ability to find vids from node pattern.
   virtual bool matchNode(NodeContext* nodeCtx) = 0;
 
+  // The derived class should implement matchEdge if the finder has
+  // ability to find vids from edge pattern.
   virtual bool matchEdge(EdgeContext* nodeCtx) = 0;
 
   StatusOr<SubPlan> transform(PatternContext* patternCtx);

src/graph/planner/match/UnwindClausePlanner.h

@@ -10,9 +10,7 @@
 
 namespace nebula {
 namespace graph {
-/*
- * The UnwindClausePlanner was designed to generate plan for unwind clause
- */
+// The UnwindClausePlanner generates plan for unwind clause
 class UnwindClausePlanner final : public CypherClausePlanner {
  public:
   UnwindClausePlanner() = default;

src/graph/planner/match/VertexIdSeek.h

@@ -11,10 +11,7 @@
 
 namespace nebula {
 namespace graph {
-/*
- * The VertexIdSeek was designed to find if could get the starting vids in
- * filter.
- */
+// The VertexIdSeek find if a plan could get the starting vids in filters.
 class VertexIdSeek final : public StartVidFinder {
  public:
   static std::unique_ptr<VertexIdSeek> make() {

src/graph/planner/match/WhereClausePlanner.h

@@ -10,9 +10,7 @@
 
 namespace nebula {
 namespace graph {
-/*
- * The WhereClausePlanner was designed to generate plan for where clause.
- */
+// The WhereClausePlanner generates plan for where clause.
 class WhereClausePlanner final : public CypherClausePlanner {
  public:
   explicit WhereClausePlanner(bool needStableFilter = false)

src/graph/planner/match/WithClausePlanner.h

@@ -10,9 +10,7 @@
 
 namespace nebula {
 namespace graph {
-/*
- * The WithClausePlanner was designed to generate plan for with clause.
- */
+// The WithClausePlanner generates plan for with clause.
 class WithClausePlanner final : public CypherClausePlanner {
  public:
   WithClausePlanner() = default;

src/graph/planner/match/YieldClausePlanner.h

@@ -10,10 +10,7 @@
 
 namespace nebula {
 namespace graph {
-/*
- * The YieldClausePlanner was designed to generate plan for yield clause in
- * cypher
- */
+// The YieldClausePlanner generates plan for yield clause
 class YieldClausePlanner final : public CypherClausePlanner {
  public:
   YieldClausePlanner() = default;

src/graph/planner/ngql/GoPlanner.cpp

@@ -90,11 +90,9 @@ Expression* GoPlanner::loopCondition(uint32_t steps, const std::string& var) {
   return LogicalExpression::makeAnd(pool, step, earlyEnd);
 }
 
-/*
- * extract vid and edge's prop from GN
- * for joinDst & joinInput
- * output colNames {srcProps, edgeProps, kVid, "JOIN_DST_VID"}
- */
+// extract vid and edge's prop from GN
+// for joinDst & joinInput
+// output colNames {srcProps, edgeProps, kVid, "JOIN_DST_VID"}
 PlanNode* GoPlanner::extractSrcEdgePropsFromGN(PlanNode* dep, const std::string& input) {
   auto& srcEdgePropsExpr = goCtx_->srcEdgePropsExpr;
   auto* pool = goCtx_->qctx->objPool();
@@ -116,11 +114,9 @@ PlanNode* GoPlanner::extractSrcEdgePropsFromGN(PlanNode* dep, const std::string&
   return project;
 }
 
-/*
- * extract vid and dst from GN
- * for trackStartVid
- * output ColNames {srcVidColName, "TRACK_DST_VID"}
- */
+// extract vid and dst from GN
+// for trackStartVid
+// output ColNames {srcVidColName, "TRACK_DST_VID"}
 PlanNode* GoPlanner::extractSrcDstFromGN(PlanNode* dep, const std::string& input) {
   auto qctx = goCtx_->qctx;
   auto* pool = qctx->objPool();
@@ -138,11 +134,9 @@ PlanNode* GoPlanner::extractSrcDstFromGN(PlanNode* dep, const std::string& input
   return dedup;
 }
 
-/*
- * extract vid from runTime input
- * for joinInput
- * output ColNames {runtimeVidName, dstVidColName}
- */
+// extract vid from runTime input
+// for joinInput
+// output ColNames {runtimeVidName, dstVidColName}
 PlanNode* GoPlanner::extractVidFromRuntimeInput(PlanNode* dep) {
   if (dep == nullptr) {
     return dep;
@@ -166,13 +160,11 @@ PlanNode* GoPlanner::extractVidFromRuntimeInput(PlanNode* dep) {
   return dedup;
 }
 
-/*
- * establish a mapping between the original vId and the expanded destination vId
- * during each step of the expansion in the n-step and mton-step scenario
- * left: n-1 steps
- * right: step n
- * output ColNames {runtimeVidName, dstVidColName}
- */
+// establish a mapping between the original vId and the expanded destination vId
+// during each step of the expansion in the n-step and mton-step scenario
+// left: n-1 steps
+// right: step n
+// output ColNames {runtimeVidName, dstVidColName}
 PlanNode* GoPlanner::trackStartVid(PlanNode* left, PlanNode* right) {
   auto qctx = goCtx_->qctx;
   auto* pool = qctx->objPool();
@@ -207,10 +199,8 @@ PlanNode* GoPlanner::trackStartVid(PlanNode* left, PlanNode* right) {
   return dedup;
 }
 
-/*
- * output ColNames {srcProps, edgeProps, kVid, "JOIN_DST_VID", "DST_VID",
- * dstProps}
- */
+// output ColNames {srcProps, edgeProps, kVid, "JOIN_DST_VID", "DST_VID",
+// dstProps}
 PlanNode* GoPlanner::buildJoinDstPlan(PlanNode* dep) {
   auto qctx = goCtx_->qctx;
   auto* pool = qctx->objPool();
@@ -279,11 +269,9 @@ PlanNode* GoPlanner::buildJoinInputPlan(PlanNode* dep) {
   return join;
 }
 
-/*
- * left's colName dstVidColName join right's colName kVid
- * left  : n-1 steps
- * right : last step
- */
+// left's colName dstVidColName join right's colName kVid
+// left  : n-1 steps
+// right : last step
 PlanNode* GoPlanner::lastStepJoinInput(PlanNode* left, PlanNode* right) {
   auto qctx = goCtx_->qctx;
   auto* pool = qctx->objPool();

src/graph/planner/ngql/PathPlanner.cpp

@@ -469,29 +469,29 @@ PlanNode* PathPlanner::buildEdgePlan(PlanNode* dep, const std::string& input) {
   return getEdge;
 }
 
-/*
-          The Plan looks like this:
-                 +--------+---------+
-             +-->+   PassThrough    +<----+
-             |   +------------------+     |
-    +--------+---------+        +---------+------------+
-    |  Project(Nodes)  |        |Project(RelationShips)|
-    +--------+---------+        +---------+------------+
-             |                            |
-    +--------+---------+        +---------+--------+
-    |      Unwind      |        |      Unwind      |
-    +--------+---------+        +---------+--------+
-             |                            |
-    +--------+---------+        +---------+--------+
-    |   GetVertices    |        |    GetEdges      |
-    +--------+---------+        +---------+--------+
-             |                            |
-             +------------+---------------+
-                          |
-                 +--------+---------+
-                 |   DataCollect    |
-                 +--------+---------+
-*/
+//
+//        The Plan looks like this:
+//               +--------+---------+
+//           +-->+   PassThrough    +<----+
+//           |   +------------------+     |
+//  +--------+---------+        +---------+------------+
+//  |  Project(Nodes)  |        |Project(RelationShips)|
+//  +--------+---------+        +---------+------------+
+//           |                            |
+//  +--------+---------+        +---------+--------+
+//  |      Unwind      |        |      Unwind      |
+//  +--------+---------+        +---------+--------+
+//           |                            |
+//  +--------+---------+        +---------+--------+
+//  |   GetVertices    |        |    GetEdges      |
+//  +--------+---------+        +---------+--------+
+//           |                            |
+//           +------------+---------------+
+//                        |
+//               +--------+---------+
+//               |   DataCollect    |
+//               +--------+---------+
+//
 PlanNode* PathPlanner::buildPathProp(PlanNode* dep) {
   auto qctx = pathCtx_->qctx;
   auto* pt = PassThroughNode::make(qctx, dep);

src/graph/planner/plan/Admin.h

@@ -10,12 +10,10 @@
 #include "graph/planner/plan/Query.h"
 #include "interface/gen-cpp2/meta_types.h"
 
-/**
- * All admin-related nodes would be put in this file.
- * These nodes would not exist in a same plan with maintain-related/
- * mutate-related/query-related nodes. And they are also isolated
- * from each other. This would be guaranteed by parser and validator.
- */
+// All admin-related nodes would be put in this file.
+// These nodes would not exist in a same plan with maintain-related/
+// mutate-related/query-related nodes. And they are also isolated
+// from each other. This would be guaranteed by parser and validator.
 namespace nebula {
 namespace graph {
 

src/graph/planner/plan/Mutate.h

@@ -10,9 +10,7 @@
 #include "graph/planner/plan/Query.h"
 #include "parser/TraverseSentences.h"
 
-/**
- * All mutate-related nodes would put in this file.
- */
+// All mutate-related nodes would put in this file.
 namespace nebula {
 namespace graph {
 class InsertVertices final : public SingleDependencyNode {