Implement FROM NAMED

src/engine/IndexScan.h

@@ -37,10 +37,14 @@ class IndexScan final : public Operation {
 
   ~IndexScan() override = default;
 
+  // Const getters for testing.
   const TripleComponent& predicate() const { return predicate_; }
   const TripleComponent& subject() const { return subject_; }
   const TripleComponent& object() const { return object_; }
   const auto& graphsToFilter() const { return graphsToFilter_; }
+  const std::vector<Variable>& additionalVariables() const {
+    return additionalVariables_;
+  }
 
   const std::vector<ColumnIndex>& additionalColumns() const {
     return additionalColumns_;

src/engine/QueryExecutionTree.h

@@ -183,7 +183,7 @@ class QueryExecutionTree {
   // _____________________________________________________________
   friend void PrintTo(const QueryExecutionTree& tree, std::ostream* os) {
     auto& s = *os;
-    s << nlohmann::ordered_json{tree.getRootOperation()->runtimeInfo()}.dump(2);
+    s << tree.getRootOperation()->getDescriptor();
   }
 
  private:

src/engine/QueryPlanner.cpp

@@ -185,13 +185,6 @@ std::vector<QueryPlanner::SubtreePlan> QueryPlanner::createExecutionTrees(
 
   checkCancellation();
 
-  const auto& fromNamed = pq.datasetClauses_.namedGraphs_;
-  if (fromNamed.has_value()) {
-    AD_CORRECTNESS_CHECK(!fromNamed.value().empty());
-    throw std::runtime_error(
-        "FROM NAMED clauses are not yet supported by QLever");
-  }
-
   return lastRow;
 }
 
@@ -732,18 +725,32 @@ auto QueryPlanner::seedWithScansAndText(
       continue;
     }
 
-    auto addIndexScan =
-        [this, pushPlan, node,
-         &relevantGraphs = activeDatasetClauses_.defaultGraphs_](
-            Permutation::Enum permutation,
-            std::optional<SparqlTripleSimple> triple = std::nullopt) {
-          if (!triple.has_value()) {
-            triple = node.triple_.getSimple();
-          }
+    auto addIndexScan = [this, pushPlan, node,
+                         &relevantGraphs =
+                             activeDatasetClauses_.defaultGraphs_](
+                            Permutation::Enum permutation,
+                            std::optional<SparqlTripleSimple> triple =
+                                std::nullopt) {
+      if (!triple.has_value()) {
+        triple = node.triple_.getSimple();
+      }
+
+      // We are inside a `GRAPH ?var {...}` clause, so all index scans have
+      // to add the graph variable as an additional column.
+      auto& additionalColumns = triple.value().additionalScanColumns_;
+      AD_CORRECTNESS_CHECK(!ad_utility::contains(
+          additionalColumns | std::views::keys, ADDITIONAL_COLUMN_GRAPH_ID));
+      if (activeGraphVariable_.has_value()) {
+        additionalColumns.emplace_back(ADDITIONAL_COLUMN_GRAPH_ID,
+                                       activeGraphVariable_.value());
+      }
 
-          pushPlan(makeSubtreePlan<IndexScan>(
-              _qec, permutation, std::move(triple.value()), relevantGraphs));
-        };
+      // TODO<joka921> Handle the case, that the Graph variable is also used
+      // inside the `GRAPH` clause, e.g. by being used inside a triple.
+
+      pushPlan(makeSubtreePlan<IndexScan>(
+          _qec, permutation, std::move(triple.value()), relevantGraphs));
+    };
 
     auto addFilter = [&filters = result.filters_](SparqlFilter filter) {
       filters.push_back(std::move(filter));
@@ -2109,11 +2116,28 @@ void QueryPlanner::GraphPatternPlanner::graphPatternOperationVisitor(Arg& arg) {
     // default graphs while planning this clause, and reset them when leaving
     // the clause.
     std::optional<ParsedQuery::DatasetClauses> datasetBackup;
+    std::optional<Variable> graphVariableBackup = planner_.activeGraphVariable_;
     if constexpr (std::is_same_v<T, p::GroupGraphPattern>) {
-      if (arg._graphIri.has_value()) {
+      if (std::holds_alternative<TripleComponent::Iri>(arg.graphSpec_)) {
         datasetBackup = planner_.activeDatasetClauses_;
         planner_.activeDatasetClauses_.defaultGraphs_.emplace(
-            {arg._graphIri.value()});
+            {std::get<TripleComponent::Iri>(arg.graphSpec_)});
+      } else if (std::holds_alternative<Variable>(arg.graphSpec_)) {
+        const auto& graphVar = std::get<Variable>(arg.graphSpec_);
+        if (checkUsePatternTrick::isVariableContainedInGraphPattern(
+                graphVar, arg._child, nullptr)) {
+          throw std::runtime_error(
+              "A variable that is used as the graph specifier of a `GRAPH ?var "
+              "{...}` clause may not appear in the body of that clause");
+        }
+        datasetBackup = planner_.activeDatasetClauses_;
+        planner_.activeDatasetClauses_.defaultGraphs_ =
+            planner_.activeDatasetClauses_.namedGraphs_;
+        // We already have backed up the `activeGraphVariable_`.
+        planner_.activeGraphVariable_ = std::get<Variable>(arg.graphSpec_);
+      } else {
+        AD_CORRECTNESS_CHECK(
+            std::holds_alternative<std::monostate>(arg.graphSpec_));
       }
     }
 
@@ -2127,6 +2151,7 @@ void QueryPlanner::GraphPatternPlanner::graphPatternOperationVisitor(Arg& arg) {
     if (datasetBackup.has_value()) {
       planner_.activeDatasetClauses_ = std::move(datasetBackup.value());
     }
+    planner_.activeGraphVariable_ = std::move(graphVariableBackup);
   } else if constexpr (std::is_same_v<T, p::Union>) {
     visitUnion(arg);
   } else if constexpr (std::is_same_v<T, p::Subquery>) {
@@ -2170,8 +2195,8 @@ void QueryPlanner::GraphPatternPlanner::visitBasicGraphPattern(
     }
   }
 
-  // Then collect the triples. Transform each triple with a property path to an
-  // equivalent form without property path (using `seedFromPropertyPath`).
+  // Then collect the triples. Transform each triple with a property path to
+  // an equivalent form without property path (using `seedFromPropertyPath`).
   for (const auto& triple : v._triples) {
     if (triple.p_._operation == PropertyPath::Operation::IRI) {
       candidateTriples_._triples.push_back(triple);
@@ -2283,8 +2308,18 @@ void QueryPlanner::GraphPatternPlanner::visitSubquery(
   // Make sure that variables that are not selected by the subquery are
   // not visible.
   auto setSelectedVariables = [&](SubtreePlan& plan) {
+    auto selectedVariables = arg.get().selectClause().getSelectedVariables();
+    // TODO<C++23> Use `optional::transform`
+    if (planner_.activeGraphVariable_.has_value()) {
+      const auto& graphVar = planner_.activeGraphVariable_.value();
+      AD_CORRECTNESS_CHECK(
+          !ad_utility::contains(selectedVariables, graphVar),
+          "This case (variable of GRAPH ?var {...} appears also in the body) "
+          "should have thrown further up in the call stack");
+      selectedVariables.push_back(graphVar);
+    }
     plan._qet->getRootOperation()->setSelectedVariablesForSubquery(
-        arg.get().selectClause().getSelectedVariables());
+        selectedVariables);
   };
   std::ranges::for_each(candidatesForSubquery, setSelectedVariables);
   // A subquery must also respect LIMIT and OFFSET clauses

src/engine/QueryPlanner.h

@@ -21,6 +21,7 @@ class QueryPlanner {
   using vector = std::vector<T>;
 
   ParsedQuery::DatasetClauses activeDatasetClauses_;
+  std::optional<Variable> activeGraphVariable_;
 
  public:
   explicit QueryPlanner(QueryExecutionContext* qec,

src/parser/GraphPattern.h

@@ -47,7 +47,6 @@ class GraphPattern {
                          const std::string& languageInQuotes);
 
   bool _optional;
-  std::optional<TripleComponent::Iri> graphIri_;
 
   // Filters always apply to the complete GraphPattern, no matter where
   // they appear. For VALUES and Triples, the order matters, so they

src/parser/GraphPatternOperation.h

@@ -76,7 +76,11 @@ struct Values {
 /// `GraphPattern`.
 struct GroupGraphPattern {
   GraphPattern _child;
-  std::optional<TripleComponent::Iri> _graphIri = std::nullopt;
+  // If not `monostate`, then this group is a `GRAPH` clause, either with a
+  // fixed graph IRI, or with a variable.
+  using GraphSpec =
+      std::variant<std::monostate, TripleComponent::Iri, Variable>;
+  GraphSpec graphSpec_ = std::monostate{};
 };
 
 /// An `OPTIONAL` clause.

src/parser/sparqlParser/SparqlQleverVisitor.cpp

@@ -762,12 +762,14 @@ parsedQuery::Service Visitor::visit(Parser::ServiceGraphPatternContext* ctx) {
 parsedQuery::GraphPatternOperation Visitor::visit(
     Parser::GraphGraphPatternContext* ctx) {
   auto varOrIri = visit(ctx->varOrIri());
+  auto group = visit(ctx->groupGraphPattern());
   if (std::holds_alternative<Variable>(varOrIri)) {
-    reportNotSupported(ctx, "GRAPH clauses with a variable are");
+    const auto& graphVar = std::get<Variable>(varOrIri);
+    addVisibleVariable(graphVar);
+    return parsedQuery::GroupGraphPattern{std::move(group), graphVar};
   }
   AD_CORRECTNESS_CHECK(std::holds_alternative<Iri>(varOrIri));
   auto& iri = std::get<Iri>(varOrIri);
-  auto group = visit(ctx->groupGraphPattern());
   return parsedQuery::GroupGraphPattern{
       std::move(group), TripleComponent::Iri::fromIriref(iri.toSparql())};
 }

test/QueryPlannerTest.cpp

@@ -1191,8 +1191,31 @@ TEST(QueryPlanner, DatasetClause) {
           scan("<c>", "?p", "<z>", {}, g2), scan("<d>", "?p", "<z2>", {}, g2),
           scan("<e>", "?p", "<z3>", {}, g1)));
 
+  auto g12 = Graphs{"<g1>", "<g2>"};
+  auto varG = std::vector{Variable{"?g"}};
+  std::vector<ColumnIndex> graphCol{ADDITIONAL_COLUMN_GRAPH_ID};
+  h::expect(
+      "SELECT * FROM <x> FROM NAMED <g1> FROM NAMED <g2> WHERE { GRAPH ?g {<a> "
+      "<b> <c>}}",
+      scan("<a>", "<b>", "<c>", {}, g12, varG, graphCol));
+
+  h::expect("SELECT * FROM <x> WHERE { GRAPH ?g {<a> <b> <c>}}",
+            scan("<a>", "<b>", "<c>", {}, std::nullopt, varG, graphCol));
+
+  // A complex example with graph variables.
+  h::expect(
+      "SELECT * FROM <g1> FROM NAMED <g2> { <a> ?p <x>. {<b> ?p <y>} GRAPH ?g "
+      "{ <c> ?p <z> "
+      "{SELECT * {<d> ?p <z2>}}} <e> ?p <z3> }",
+      h::UnorderedJoins(scan("<a>", "?p", "<x>", {}, g1),
+                        scan("<b>", "?p", "<y>", {}, g1),
+                        scan("<c>", "?p", "<z>", {}, g2, varG, graphCol),
+                        scan("<d>", "?p", "<z2>", {}, g2, varG, graphCol),
+                        scan("<e>", "?p", "<z3>", {}, g1)));
+  // We currently don't support repeating the graph variable inside the
+  // graph clause
   AD_EXPECT_THROW_WITH_MESSAGE(
-      h::expect("SELECT * FROM <x> FROM NAMED <y> WHERE { ?x ?y ?z}",
-                ::testing::_),
-      ::testing::HasSubstr("FROM NAMED clauses are not yet supported"));
+      h::expect("SELECT * { GRAPH ?x {?x <b> <c>}}", ::testing::_),
+      AllOf(HasSubstr("used as the graph specifier"),
+            HasSubstr("may not appear in the body")));
 }

test/QueryPlannerTestHelpers.h

@@ -83,11 +83,13 @@ constexpr auto IndexScan =
     [](TripleComponent subject, TripleComponent predicate,
        TripleComponent object,
        const std::vector<Permutation::Enum>& allowedPermutations = {},
-       const ScanSpecificationAsTripleComponent::Graphs& graphs =
-           std::nullopt) -> QetMatcher {
+       const ScanSpecificationAsTripleComponent::Graphs& graphs = std::nullopt,
+       const std::vector<Variable>& additionalVariables = {},
+       const std::vector<ColumnIndex>& additionalColumns = {}) -> QetMatcher {
   size_t numVariables = static_cast<size_t>(subject.isVariable()) +
                         static_cast<size_t>(predicate.isVariable()) +
-                        static_cast<size_t>(object.isVariable());
+                        static_cast<size_t>(object.isVariable()) +
+                        additionalColumns.size();
   auto permutationMatcher = allowedPermutations.empty()
                                 ? ::testing::A<Permutation::Enum>()
                                 : AnyOfArray(allowedPermutations);
@@ -97,6 +99,10 @@ constexpr auto IndexScan =
             AD_PROPERTY(IndexScan, subject, Eq(subject)),
             AD_PROPERTY(IndexScan, predicate, Eq(predicate)),
             AD_PROPERTY(IndexScan, object, Eq(object)),
+            AD_PROPERTY(IndexScan, additionalVariables,
+                        ElementsAreArray(additionalVariables)),
+            AD_PROPERTY(IndexScan, additionalColumns,
+                        ElementsAreArray(additionalColumns)),
             AD_PROPERTY(IndexScan, graphsToFilter, Eq(graphs))));
 };
 
@@ -193,7 +199,9 @@ inline auto IndexScanFromStrings =
        std::string_view object,
        const std::vector<Permutation::Enum>& allowedPermutations = {},
        const std::optional<ad_utility::HashSet<std::string>> graphs =
-           std::nullopt) -> QetMatcher {
+           std::nullopt,
+       const std::vector<Variable>& additionalVariables = {},
+       const std::vector<ColumnIndex>& additionalColumns = {}) -> QetMatcher {
   auto strToComp = [](std::string_view s) -> TripleComponent {
     if (s.starts_with("?")) {
       return ::Variable{std::string{s}};
@@ -211,7 +219,8 @@ inline auto IndexScanFromStrings =
     }
   }
   return IndexScan(strToComp(subject), strToComp(predicate), strToComp(object),
-                   allowedPermutations, graphsOut);
+                   allowedPermutations, graphsOut, additionalVariables,
+                   additionalColumns);
 };
 
 // For the following Join algorithms the order of the children is not important.
@@ -231,11 +240,12 @@ inline auto UnorderedJoins = [](auto&&... children) -> QetMatcher {
                                      Vec& children, const auto& self) -> void {
     const Operation* operation = tree.getRootOperation().get();
     auto join = dynamic_cast<const ::Join*>(operation);
+    auto multiColJoin = dynamic_cast<const ::MultiColumnJoin*>(operation);
     // Also allow the INTERNAL SORT BY operations that are needed for the joins.
     // TODO<joka921> is this the right place to also check that those have the
     // correct columns?
     auto sort = dynamic_cast<const ::Sort*>(operation);
-    if (!join && !sort) {
+    if (!join && !sort && !multiColJoin) {
       children.push_back(tree);
     } else {
       for (const auto& child : operation->getChildren()) {

test/SparqlAntlrParserTest.cpp

@@ -1010,9 +1010,10 @@ TEST(SparqlParser, GroupGraphPattern) {
   // SERVICE with a variable endpoint is not yet supported.
   expectGroupGraphPatternFails("{ SERVICE ?endpoint { ?s ?p ?o } }");
 
-  // graphGraphPattern is currently only supported with a fixed graph IRI, not
-  // with a variable.
-  expectGroupGraphPatternFails("{ GRAPH ?a { } }");
+  expectGraphPattern("{ GRAPH ?g { ?x <is-a> <Actor> }}",
+                     m::GraphPattern(m::GroupGraphPatternWithGraph(
+                         Variable("?g"),
+                         m::Triples({{Var{"?x"}, "<is-a>", iri("<Actor>")}}))));
   expectGraphPattern(
       "{ GRAPH <foo> { ?x <is-a> <Actor> }}",
       m::GraphPattern(m::GroupGraphPatternWithGraph(

test/SparqlAntlrParserTestHelpers.h

@@ -676,11 +676,11 @@ inline auto Optional =
 
 inline auto Group =
     [](auto&& subMatcher,
-       std::optional<TripleComponent::Iri> graphIri =
-           std::nullopt) -> Matcher<const p::GraphPatternOperation&> {
+       p::GroupGraphPattern::GraphSpec graphSpec =
+           std::monostate{}) -> Matcher<const p::GraphPatternOperation&> {
   return detail::GraphPatternOperation<p::GroupGraphPattern>(::testing::AllOf(
       AD_FIELD(p::GroupGraphPattern, _child, subMatcher),
-      AD_FIELD(p::GroupGraphPattern, _graphIri, ::testing::Eq(graphIri))));
+      AD_FIELD(p::GroupGraphPattern, graphSpec_, ::testing::Eq(graphSpec))));
 };
 
 inline auto Union =
@@ -764,9 +764,9 @@ inline auto GroupGraphPattern = [](vector<std::string>&& filters,
   return Group(detail::GraphPattern(false, filters, childMatchers...));
 };
 
-inline auto GroupGraphPatternWithGraph = [](vector<std::string>&& filters,
-                                            const TripleComponent::Iri& graph,
-                                            const auto&... childMatchers)
+inline auto GroupGraphPatternWithGraph =
+    [](vector<std::string>&& filters, p::GroupGraphPattern::GraphSpec graph,
+       const auto&... childMatchers)
     -> Matcher<const p::GraphPatternOperation&> {
   return Group(detail::GraphPattern(false, filters, childMatchers...), graph);
 };