Add code comments of validators.

src/graph/validator/AdminValidator.cpp

@@ -15,6 +15,8 @@
 
 namespace nebula {
 namespace graph {
+
+// Validate options of create space sentence, and fill them into spaceDesc_
 Status CreateSpaceValidator::validateImpl() {
   auto sentence = static_cast<CreateSpaceSentence *>(sentence_);
   ifNotExist_ = sentence->isIfNotExist();
@@ -150,6 +152,7 @@ Status CreateSpaceValidator::toPlan() {
   return Status::OK();
 }
 
+// Validate sentence to create space by clone existed one. Just clone meta data, don't clone data.
 Status CreateSpaceAsValidator::validateImpl() {
   auto sentence = static_cast<CreateSpaceAsSentence *>(sentence_);
   oldSpaceName_ = sentence->getOldSpaceName();
@@ -164,6 +167,7 @@ Status CreateSpaceAsValidator::toPlan() {
   return Status::OK();
 }
 
+// Alter options of space: zone
 Status AlterSpaceValidator::validateImpl() {
   return Status::OK();
 }
@@ -212,10 +216,13 @@ Status DropSpaceValidator::toPlan() {
   return Status::OK();
 }
 
+// Show the sentence to create this space. It's created from options of space, so maybe is different
+// from the origin sentence to create this space.
 Status ShowCreateSpaceValidator::validateImpl() {
   return Status::OK();
 }
 
+// Show create space need read permission on target space.
 Status ShowCreateSpaceValidator::checkPermission() {
   auto sentence = static_cast<ShowCreateSpaceSentence *>(sentence_);
   auto spaceIdResult = qctx_->schemaMng()->toGraphSpaceID(*sentence->spaceName());
@@ -323,6 +330,7 @@ Status ShowListenerValidator::toPlan() {
   return Status::OK();
 }
 
+// Register hosts, unregistered host won't be allowed to join cluster.
 Status AddHostsValidator::validateImpl() {
   auto sentence = static_cast<AddHostsSentence *>(sentence_);
   auto hosts = sentence->hosts()->hosts();
@@ -527,6 +535,7 @@ Status ShowStatusValidator::validateImpl() {
   return Status::OK();
 }
 
+// Plan to show stats of vertices and edges
 Status ShowStatusValidator::toPlan() {
   auto *node = ShowStats::make(qctx_, nullptr);
   root_ = node;
@@ -538,6 +547,7 @@ Status ShowServiceClientsValidator::validateImpl() {
   return Status::OK();
 }
 
+// Plan to show external service clients, e.g. Text Search client
 Status ShowServiceClientsValidator::toPlan() {
   auto sentence = static_cast<ShowServiceClientsSentence *>(sentence_);
   auto type = sentence->getType();
@@ -551,6 +561,7 @@ Status SignInServiceValidator::validateImpl() {
   return Status::OK();
 }
 
+// Plan to sign in external services, e.g. Text Search
 Status SignInServiceValidator::toPlan() {
   auto sentence = static_cast<SignInServiceSentence *>(sentence_);
   std::vector<meta::cpp2::ServiceClient> clients;
@@ -568,6 +579,7 @@ Status SignOutServiceValidator::validateImpl() {
   return Status::OK();
 }
 
+// Plan to sign out external services, e.g. Text Search
 Status SignOutServiceValidator::toPlan() {
   auto sentence = static_cast<SignOutServiceSentence *>(sentence_);
   auto type = sentence->getType();
@@ -639,6 +651,7 @@ Status KillQueryValidator::validateImpl() {
   return Status::OK();
 }
 
+// Plan to kill query by execution plan id
 Status KillQueryValidator::toPlan() {
   auto sentence = static_cast<KillQuerySentence *>(sentence_);
   auto *node = KillQuery::make(qctx_, nullptr, sentence->sessionId(), sentence->epId());

src/graph/validator/AssignmentValidator.cpp

@@ -21,6 +21,7 @@ Status AssignmentValidator::validateImpl() {
   return Status::OK();
 }
 
+// Plan to process assignment in nGQL, e.g. $a = GO FROM <vid_list> OVER <edge_type> YIELD ...
 Status AssignmentValidator::toPlan() {
   root_ = validator_->root();
   auto *var = qctx_->symTable()->newVariable(var_);

src/graph/validator/DownloadValidator.cpp

@@ -11,6 +11,7 @@
 namespace nebula {
 namespace graph {
 
+// Plan to download SST file from HDFS
 Status DownloadValidator::toPlan() {
   auto sentence = static_cast<DownloadSentence *>(sentence_);
   if (sentence->host() == nullptr || sentence->port() == 0 || sentence->path() == nullptr) {

src/graph/validator/ExplainValidator.cpp

@@ -31,6 +31,7 @@ ExplainValidator::ExplainValidator(Sentence* sentence, QueryContext* context)
   }
 }
 
+// Check validity of format type string, and convert to lower case
 static StatusOr<std::string> toExplainFormatType(const std::string& formatType) {
   if (formatType.empty()) {
     return kAllowedFmtType.front();

src/graph/validator/FetchEdgesValidator.cpp

@@ -27,6 +27,7 @@ Status FetchEdgesValidator::validateImpl() {
   return Status::OK();
 }
 
+// Check validity of edge type specified in sentence
 Status FetchEdgesValidator::validateEdgeName() {
   auto &spaceID = space_.id;
   auto status = qctx_->schemaMng()->toEdgeType(spaceID, edgeName_);
@@ -39,6 +40,8 @@ Status FetchEdgesValidator::validateEdgeName() {
   return Status::OK();
 }
 
+// Check validity of edge key(src, type, rank, dst)
+// from Input/Variable expression specified in sentence
 StatusOr<std::string> FetchEdgesValidator::validateEdgeRef(const Expression *expr,
                                                            Value::Type type) {
   const auto &kind = expr->kind();
@@ -62,11 +65,12 @@ StatusOr<std::string> FetchEdgesValidator::validateEdgeRef(const Expression *exp
   return propExpr->sym();
 }
 
+// Check validity of edge key(src, type, rank, dst) from Variable/Constants specified in sentence
 Status FetchEdgesValidator::validateEdgeKey() {
   auto pool = qctx_->objPool();
   auto *sentence = static_cast<FetchEdgesSentence *>(sentence_);
   std::string inputVarName;
-  if (sentence->isRef()) {
+  if (sentence->isRef()) {  // edge keys from Input/Variable
     auto *srcExpr = sentence->ref()->srcid();
     auto result = validateEdgeRef(srcExpr, vidType_);
     NG_RETURN_IF_ERROR(result);
@@ -97,45 +101,48 @@ Status FetchEdgesValidator::validateEdgeKey() {
     fetchCtx_->type = ConstantExpression::make(pool, edgeType_);
     fetchCtx_->inputVarName = std::move(inputVarName);
     return Status::OK();
-  }
-
-  DataSet edgeKeys{{kSrc, kRank, kDst}};
-  QueryExpressionContext ctx;
-  auto keys = sentence->keys()->keys();
-  edgeKeys.rows.reserve(keys.size());
-  for (const auto &key : keys) {
-    if (!ExpressionUtils::isEvaluableExpr(key->srcid(), qctx_)) {
-      return Status::SemanticError("`%s' is not evaluable.", key->srcid()->toString().c_str());
-    }
-    auto src = key->srcid()->eval(ctx);
-    if (src.type() != vidType_) {
-      std::stringstream ss;
-      ss << "the src should be type of " << vidType_ << ", but was`" << src.type() << "'";
-      return Status::SemanticError(ss.str());
-    }
-    auto ranking = key->rank();
+  } else {  // Edge keys from constants
+    DataSet edgeKeys{{kSrc, kRank, kDst}};
+    QueryExpressionContext ctx;
+    auto keys = sentence->keys()->keys();
+    edgeKeys.rows.reserve(keys.size());
+    for (const auto &key : keys) {
+      if (!ExpressionUtils::isEvaluableExpr(key->srcid(), qctx_)) {
+        return Status::SemanticError("`%s' is not evaluable.", key->srcid()->toString().c_str());
+      }
+      auto src = key->srcid()->eval(ctx);
+      if (src.type() != vidType_) {
+        std::stringstream ss;
+        ss << "the src should be type of " << vidType_ << ", but was`" << src.type() << "'";
+        return Status::SemanticError(ss.str());
+      }
+      auto ranking = key->rank();
 
-    if (!ExpressionUtils::isEvaluableExpr(key->dstid(), qctx_)) {
-      return Status::SemanticError("`%s' is not evaluable.", key->dstid()->toString().c_str());
-    }
-    auto dst = key->dstid()->eval(ctx);
-    if (dst.type() != vidType_) {
-      std::stringstream ss;
-      ss << "the dst should be type of " << vidType_ << ", but was`" << dst.type() << "'";
-      return Status::SemanticError(ss.str());
+      if (!ExpressionUtils::isEvaluableExpr(key->dstid(), qctx_)) {
+        return Status::SemanticError("`%s' is not evaluable.", key->dstid()->toString().c_str());
+      }
+      auto dst = key->dstid()->eval(ctx);
+      if (dst.type() != vidType_) {
+        std::stringstream ss;
+        ss << "the dst should be type of " << vidType_ << ", but was`" << dst.type() << "'";
+        return Status::SemanticError(ss.str());
+      }
+      edgeKeys.emplace_back(nebula::Row({std::move(src), ranking, std::move(dst)}));
     }
-    edgeKeys.emplace_back(nebula::Row({std::move(src), ranking, std::move(dst)}));
+    inputVarName = vctx_->anonVarGen()->getVar();
+    qctx_->ectx()->setResult(inputVarName,
+                             ResultBuilder().value(Value(std::move(edgeKeys))).build());
+    fetchCtx_->src = ColumnExpression::make(pool, 0);
+    fetchCtx_->rank = ColumnExpression::make(pool, 1);
+    fetchCtx_->dst = ColumnExpression::make(pool, 2);
+    fetchCtx_->type = ConstantExpression::make(pool, edgeType_);
+    fetchCtx_->inputVarName = std::move(inputVarName);
+    return Status::OK();
   }
-  inputVarName = vctx_->anonVarGen()->getVar();
-  qctx_->ectx()->setResult(inputVarName, ResultBuilder().value(Value(std::move(edgeKeys))).build());
-  fetchCtx_->src = ColumnExpression::make(pool, 0);
-  fetchCtx_->rank = ColumnExpression::make(pool, 1);
-  fetchCtx_->dst = ColumnExpression::make(pool, 2);
-  fetchCtx_->type = ConstantExpression::make(pool, edgeType_);
-  fetchCtx_->inputVarName = std::move(inputVarName);
-  return Status::OK();
 }
 
+// Validate columns of yield clause, rewrites expression to fit its sementic
+// and disable some invalid expression types.
 Status FetchEdgesValidator::validateYield(const YieldClause *yield) {
   if (yield == nullptr) {
     return Status::SemanticError("Missing yield clause.");

src/graph/validator/FetchVerticesValidator.cpp

@@ -23,6 +23,7 @@ Status FetchVerticesValidator::validateImpl() {
   return Status::OK();
 }
 
+// Check validity of tags specified in sentence
 Status FetchVerticesValidator::validateTag(const NameLabelList *nameLabels) {
   if (nameLabels == nullptr) {
     // all tag
@@ -50,6 +51,8 @@ Status FetchVerticesValidator::validateTag(const NameLabelList *nameLabels) {
   return Status::OK();
 }
 
+// Validate columns of yield clause, rewrites expression to fit its sementic
+// and disable some invalid expression types.
 Status FetchVerticesValidator::validateYield(YieldClause *yield) {
   if (yield == nullptr) {
     return Status::SemanticError("Missing yield clause.");

src/graph/validator/FindPathValidator.cpp

@@ -30,6 +30,8 @@ Status FindPathValidator::validateImpl() {
   return Status::OK();
 }
 
+// Check validity of filter expression, rewrites expression to fit its sementic,
+// disable some invalid expression types, collect properties used in filter.
 Status FindPathValidator::validateWhere(WhereClause* where) {
   if (where == nullptr) {
     return Status::OK();
@@ -62,6 +64,7 @@ Status FindPathValidator::validateWhere(WhereClause* where) {
   return Status::OK();
 }
 
+// Check validity of yield columns
 Status FindPathValidator::validateYield(YieldClause* yield) {
   if (yield == nullptr) {
     return Status::SemanticError("Missing yield clause.");

src/graph/validator/GetSubgraphValidator.cpp

@@ -27,6 +27,7 @@ Status GetSubgraphValidator::validateImpl() {
   return Status::OK();
 }
 
+// Validate in-bound edge types
 Status GetSubgraphValidator::validateInBound(InBoundClause* in) {
   auto& edgeTypes = subgraphCtx_->edgeTypes;
   if (in != nullptr) {
@@ -49,6 +50,7 @@ Status GetSubgraphValidator::validateInBound(InBoundClause* in) {
   return Status::OK();
 }
 
+// Validate out-bound edge types
 Status GetSubgraphValidator::validateOutBound(OutBoundClause* out) {
   auto& edgeTypes = subgraphCtx_->edgeTypes;
   if (out != nullptr) {
@@ -70,6 +72,7 @@ Status GetSubgraphValidator::validateOutBound(OutBoundClause* out) {
   return Status::OK();
 }
 
+// Validate bidirectional(in-bound and out-bound) edge types
 Status GetSubgraphValidator::validateBothInOutBound(BothInOutClause* out) {
   auto& edgeTypes = subgraphCtx_->edgeTypes;
   if (out != nullptr) {
@@ -93,6 +96,7 @@ Status GetSubgraphValidator::validateBothInOutBound(BothInOutClause* out) {
   return Status::OK();
 }
 
+// Validate yield clause, which only supports YIELD vertices or edges
 Status GetSubgraphValidator::validateYield(YieldClause* yield) {
   if (yield == nullptr) {
     return Status::SemanticError("Missing yield clause.");

src/graph/validator/GoValidator.cpp

@@ -32,6 +32,7 @@ Status GoValidator::validateImpl() {
     return Status::SemanticError("$- must be referred in FROM before used in WHERE or YIELD");
   }
 
+  // Only one variable allowed in whole sentence
   if (!exprProps.varProps().empty()) {
     if (goCtx_->from.fromType != kVariable) {
       return Status::SemanticError(
@@ -60,6 +61,8 @@ Status GoValidator::validateImpl() {
   return Status::OK();
 }
 
+// Validate filter expression, rewrites expression to fit sementic,
+// deduce and check the type of expression, collect properties used in filter.
 Status GoValidator::validateWhere(WhereClause* where) {
   if (where == nullptr) {
     return Status::OK();
@@ -87,6 +90,7 @@ Status GoValidator::validateWhere(WhereClause* where) {
   return Status::OK();
 }
 
+// Validate the step sample/limit clause, which specify the sample/limit number for each steps.
 Status GoValidator::validateTruncate(TruncateClause* truncate) {
   if (truncate == nullptr) {
     return Status::OK();
@@ -119,6 +123,8 @@ Status GoValidator::validateTruncate(TruncateClause* truncate) {
   return Status::OK();
 }
 
+// Validate yield clause, disable the invalid expression types, rewrites expression to fit sementic,
+// check expression type, collect properties used in yield.
 Status GoValidator::validateYield(YieldClause* yield) {
   if (yield == nullptr) {
     return Status::SemanticError("Missing yield clause.");
@@ -156,6 +162,7 @@ Status GoValidator::validateYield(YieldClause* yield) {
   return Status::OK();
 }
 
+// Get all tag IDs in the whole space
 Status GoValidator::extractTagIds() {
   auto tagStatus = qctx_->schemaMng()->getAllLatestVerTagSchema(space_.id);
   NG_RETURN_IF_ERROR(tagStatus);
@@ -176,6 +183,8 @@ void GoValidator::extractPropExprs(const Expression* expr,
   const_cast<Expression*>(expr)->accept(&visitor);
 }
 
+// Rewrites the property expression to corresponding Variable/Input expression
+// which get related property from previous plan node.
 Expression* GoValidator::rewrite2VarProp(const Expression* expr) {
   auto matcher = [this](const Expression* e) -> bool {
     return propExprColMap_.find(e->toString()) != propExprColMap_.end();
@@ -189,6 +198,9 @@ Expression* GoValidator::rewrite2VarProp(const Expression* expr) {
   return RewriteVisitor::transform(expr, matcher, rewriter);
 }
 
+// Build the final output columns, collect the src/edge and dst properties used in the query,
+// collect the input properties used in the query,
+// rewrites output expression to Input/Variable expression to get properties from previous plan node
 Status GoValidator::buildColumns() {
   const auto& exprProps = goCtx_->exprProps;
   const auto& dstTagProps = exprProps.dstTagProps();

src/graph/validator/GroupByValidator.cpp

@@ -23,6 +23,8 @@ Status GroupByValidator::validateImpl() {
   return Status::OK();
 }
 
+// Validate the yield clause of group by.
+// Check aggregate expression, and add Input/Variable expression for Project
 Status GroupByValidator::validateYield(const YieldClause* yieldClause) {
   std::vector<YieldColumn*> columns;
   if (yieldClause != nullptr) {
@@ -78,6 +80,8 @@ Status GroupByValidator::validateYield(const YieldClause* yieldClause) {
   return Status::OK();
 }
 
+// Validate group by expression.
+// The expression must contains Input/Variable expression, and shouldn't contains some expressions.
 Status GroupByValidator::validateGroup(const GroupClause* groupClause) {
   if (!groupClause) return Status::OK();
   std::vector<YieldColumn*> columns;
@@ -141,6 +145,10 @@ Status GroupByValidator::toPlan() {
   return Status::OK();
 }
 
+// Check the correctness of group by clause and yield clause.
+// Check expression type,  disable invalid properties.
+// Check group by expression and yield expression, variable expression in yield columns must
+// contains in group by expressions too.
 Status GroupByValidator::groupClauseSemanticCheck() {
   // deduce group items and build outputs_
   DCHECK_EQ(aggOutputColNames_.size(), groupItems_.size());

src/graph/validator/IngestValidator.cpp

@@ -10,6 +10,7 @@
 namespace nebula {
 namespace graph {
 
+// Plan to ingest SST file in server side
 Status IngestValidator::toPlan() {
   auto *doNode = Ingest::make(qctx_, nullptr);
   root_ = doNode;

src/graph/validator/LimitValidator.cpp

@@ -10,6 +10,7 @@
 
 namespace nebula {
 namespace graph {
+// Validate limit number
 Status LimitValidator::validateImpl() {
   auto limitSentence = static_cast<LimitSentence *>(sentence_);
   offset_ = limitSentence->offset();