Fix failure when all field are constant expressions in yield sentence with filter (#260)

* Fix yield sentence with where in constant expression

* address yee's commnet

Co-authored-by: dutor <440396+dutor@users.noreply.github.com>

src/executor/query/FilterExecutor.cpp

@@ -18,11 +18,15 @@ folly::Future<Status> FilterExecutor::execute() {
     SCOPED_TIMER(&execTime_);
     auto* filter = asNode<Filter>(node());
     auto iter = ectx_->getResult(filter->inputVar()).iter();
-
-    if (iter == nullptr) {
-        LOG(ERROR) << "Internal Error: iterator is nullptr";
-        return Status::Error("Internal Error: iterator is nullptr");
+    if (iter == nullptr || iter->isDefaultIter()) {
+        LOG(ERROR) << "Internal Error: iterator is nullptr or DefaultIter";
+        return Status::Error("Internal Error: iterator is nullptr or DefaultIter");
     }
+
+    VLOG(2) << "Get input var: " << filter->inputVar()
+            << ", iterator type: " << static_cast<int16_t>(iter->kind())
+            << ", input data size: " << iter->size();
+
     ResultBuilder builder;
     builder.value(iter->valuePtr());
     QueryExpressionContext ctx(ectx_);

src/validator/YieldValidator.cpp

@@ -44,6 +44,11 @@ Status YieldValidator::validateImpl() {
         NG_RETURN_IF_ERROR(checkAggFunAndBuildGroupItems(yield->yield()));
     }
 
+    if (exprProps_.inputProps().empty() && exprProps_.varProps().empty()) {
+        // generate constant expression result into querycontext
+        genConstantExprValues();
+    }
+
     return Status::OK();
 }
 
@@ -110,6 +115,20 @@ Status YieldValidator::makeOutputColumn(YieldColumn *column) {
     return Status::OK();
 }
 
+void YieldValidator::genConstantExprValues() {
+    constantExprVar_ = vctx_->anonVarGen()->getVar();
+    DataSet ds;
+    ds.colNames = outputColumnNames_;
+    QueryExpressionContext ctx;
+    Row row;
+    for (auto& column : columns_->columns()) {
+        row.values.emplace_back(Expression::eval(column->expr(), ctx(nullptr)));
+    }
+    ds.emplace_back(std::move(row));
+    qctx_->ectx()->setResult(constantExprVar_,
+                             ResultBuilder().value(Value(std::move(ds))).finish());
+}
+
 Status YieldValidator::validateYieldAndBuildOutputs(const YieldClause *clause) {
     auto columns = clause->columns();
     columns_ = qctx_->objPool()->add(new YieldColumns);
@@ -162,6 +181,7 @@ Status YieldValidator::validateYieldAndBuildOutputs(const YieldClause *clause) {
 
         NG_RETURN_IF_ERROR(makeOutputColumn(column->clone().release()));
     }
+
     return Status::OK();
 }
 
@@ -186,6 +206,9 @@ Status YieldValidator::toPlan() {
         std::transform(
             inputs_.cbegin(), inputs_.cend(), colNames.begin(), [](auto &in) { return in.first; });
         filter->setColNames(std::move(colNames));
+        if (!constantExprVar_.empty()) {
+            filter->setInputVar(constantExprVar_);
+        }
     }
 
     SingleInputNode *dedupDep = nullptr;
@@ -224,3 +247,4 @@ Status YieldValidator::toPlan() {
 
 }   // namespace graph
 }   // namespace nebula
+

src/validator/YieldValidator.h

@@ -41,13 +41,15 @@ private:
     Status checkInputProps() const;
     Status checkAggFunAndBuildGroupItems(const YieldClause *clause);
     Status makeOutputColumn(YieldColumn *column);
+    void genConstantExprValues();
 
+private:
     bool hasAggFun_{false};
-
     YieldColumns *columns_{nullptr};
     std::vector<std::string> outputColumnNames_;
     std::vector<Aggregate::GroupItem> groupItems_;
     ExpressionProps  exprProps_;
+    std::string constantExprVar_;
 };
 
 }   // namespace graph

tests/query/v1/test_yield.py

@@ -581,3 +581,31 @@ class TestYield(NebulaTestSuite):
         resp = self.execute_query(query)
         self.check_resp_succeeded(resp)
         self.check_result(resp, [['hello']])
+
+    def test_constant_expression_with_where(self):
+        query = 'YIELD 1+1, "Hello world!" WHERE true;'
+        resp = self.execute_query(query)
+        self.check_resp_succeeded(resp)
+        self.check_result(resp, [[2, 'Hello world!']])
+
+        query = 'YIELD 1+1, "Hello world!" WHERE NULL;'
+        resp = self.execute_query(query)
+        self.check_resp_succeeded(resp)
+        self.check_empty_result(resp)
+
+        query = '''GO FROM "Tim Duncan", "Tim Duncan" OVER serve YIELD $$.team.name AS team
+                   | YIELD 1+1, "Hello world!" WHERE $-.team == "Spurs"'''
+        resp = self.execute_query(query)
+        self.check_resp_succeeded(resp)
+        columns = ['(1+1)', 'Hello world!']
+        self.check_column_names(resp, columns)
+        expect_result = [[2, 'Hello world!'], [2, 'Hello world!']]
+        self.check_out_of_order_result(resp, expect_result)
+
+        query = '''GO FROM "Tim Duncan", "Tim Duncan" OVER serve YIELD $$.team.name AS team
+                   | YIELD 1+1, "Hello world!" WHERE $-.team != "Spurs"'''
+        resp = self.execute_query(query)
+        self.check_resp_succeeded(resp)
+        columns = ['(1+1)', 'Hello world!']
+        self.check_column_names(resp, columns)
+        self.check_empty_result(resp)