Add CreateIndex operator

Reviewers: florijan, mislav.bradac, buda

Reviewed By: florijan, buda

Subscribers: pullbot

Differential Revision: https://phabricator.memgraph.io/D516

src/database/graph_db_accessor.hpp

@@ -14,6 +14,11 @@
 #include "storage/edge_accessor.hpp"
 #include "storage/vertex_accessor.hpp"
 
+/** Thrown when creating an index which already exists. */
+class IndexExistsException : public utils::BasicException {
+  using utils::BasicException::BasicException;
+};
+
 /**
  * An accessor for the database object: exposes functions
  * for operating on the database. All the functions in
@@ -253,7 +258,7 @@ class GraphDbAccessor {
                   const GraphDbTypes::Property &property) {
     const LabelPropertyIndex::Key key(label, property);
     if (db_.label_property_index_.CreateIndex(key) == false) {
-      throw utils::BasicException(
+      throw IndexExistsException(
           "Index is either being created by another transaction or already "
           "exists.");
     }

src/query/interpreter.hpp

@@ -136,7 +136,8 @@ class Interpreter {
                dynamic_cast<plan::RemoveProperty *>(logical_plan.get()) ||
                dynamic_cast<plan::RemoveLabels *>(logical_plan.get()) ||
                dynamic_cast<plan::Delete *>(logical_plan.get()) ||
-               dynamic_cast<plan::Merge *>(logical_plan.get())) {
+               dynamic_cast<plan::Merge *>(logical_plan.get()) ||
+               dynamic_cast<plan::CreateIndex *>(logical_plan.get())) {
       stream.Header(header);
       auto cursor = logical_plan->MakeCursor(db_accessor);
       while (cursor->Pull(frame, symbol_table)) continue;

src/query/plan/cost_estimator.cpp

@@ -58,5 +58,6 @@ bool CostEstimator::PostVisit(Unwind &unwind) {
 }
 
 bool CostEstimator::Visit(Once &) { return true; }
+bool CostEstimator::Visit(CreateIndex &) { return true; }
 
 }  // namespace query::plan

src/query/plan/cost_estimator.hpp

@@ -64,6 +64,7 @@ class CostEstimator : public HierarchicalLogicalOperatorVisitor {
   bool PostVisit(ExpandUniquenessFilter<EdgeAccessor> &) override;
   bool PostVisit(Unwind &unwind) override;
   bool Visit(Once &) override;
+  bool Visit(CreateIndex &) override;
 
   auto cost() const { return cost_; }
   auto cardinality() const { return cardinality_; }

src/query/plan/operator.cpp

@@ -1637,4 +1637,40 @@ void Distinct::DistinctCursor::Reset() {
   seen_rows_.clear();
 }
 
+CreateIndex::CreateIndex(GraphDbTypes::Label label,
+                         GraphDbTypes::Property property)
+    : label_(label), property_(property) {}
+
+bool CreateIndex::Accept(HierarchicalLogicalOperatorVisitor &visitor) {
+  return visitor.Visit(*this);
+}
+
+class CreateIndexCursor : public Cursor {
+ public:
+  CreateIndexCursor(CreateIndex &self, GraphDbAccessor &db)
+      : self_(self), db_(db) {}
+
+  bool Pull(Frame &, const SymbolTable &) override {
+    if (did_create_) return false;
+    try {
+      db_.BuildIndex(self_.label(), self_.property());
+    } catch (const IndexExistsException &) {
+      // Ignore creating an existing index.
+    }
+    did_create_ = true;
+    return true;
+  }
+
+  void Reset() override { did_create_ = false; }
+
+ private:
+  const CreateIndex &self_;
+  GraphDbAccessor &db_;
+  bool did_create_ = false;
+};
+
+std::unique_ptr<Cursor> CreateIndex::MakeCursor(GraphDbAccessor &db) {
+  return std::make_unique<CreateIndexCursor>(*this, db);
+}
+
 }  // namespace query::plan

src/query/plan/operator.hpp

@@ -75,6 +75,7 @@ class Merge;
 class Optional;
 class Unwind;
 class Distinct;
+class CreateIndex;
 
 using LogicalOperatorCompositeVisitor = ::utils::CompositeVisitor<
     Once, CreateNode, CreateExpand, ScanAll, ScanAllByLabel, Expand, Filter,
@@ -83,7 +84,7 @@ using LogicalOperatorCompositeVisitor = ::utils::CompositeVisitor<
     ExpandUniquenessFilter<EdgeAccessor>, Accumulate, AdvanceCommand, Aggregate,
     Skip, Limit, OrderBy, Merge, Optional, Unwind, Distinct>;
 
-using LogicalOperatorLeafVisitor = ::utils::LeafVisitor<Once>;
+using LogicalOperatorLeafVisitor = ::utils::LeafVisitor<Once, CreateIndex>;
 
 /**
  * @brief Base class for hierarhical visitors of @c LogicalOperator class
@@ -1287,5 +1288,27 @@ class Distinct : public LogicalOperator {
   };
 };
 
+/**
+ * Creates an index for a combination of label and a property.
+ *
+ * This operator takes no input and it shouldn't serve as an input to any
+ * operator. Pulling from the cursor of this operator will create an index in
+ * the database for the vertices which have the given label and property. In
+ * case the index already exists, nothing happens.
+ */
+class CreateIndex : public LogicalOperator {
+ public:
+  CreateIndex(GraphDbTypes::Label label, GraphDbTypes::Property property);
+  bool Accept(HierarchicalLogicalOperatorVisitor &visitor) override;
+  std::unique_ptr<Cursor> MakeCursor(GraphDbAccessor &db) override;
+
+  auto label() const { return label_; }
+  auto property() const { return property_; }
+
+ private:
+  GraphDbTypes::Label label_;
+  GraphDbTypes::Property property_;
+};
+
 }  // namespace plan
 }  // namespace query

tests/unit/query_plan_create_set_remove_delete.cpp

@@ -934,3 +934,16 @@ TEST(QueryPlan, RemoveLabelsOnNull) {
   EXPECT_EQ(0, CountIterable(dba->vertices(false)));
   EXPECT_EQ(1, PullAll(remove_op, *dba, symbol_table));
 }
+
+TEST(QueryPlan, CreateIndex) {
+  // CREATE INDEX ON :label(property)
+  Dbms dbms;
+  auto dba = dbms.active();
+  auto label = dba->label("label");
+  auto property = dba->property("property");
+  EXPECT_FALSE(dba->LabelPropertyIndexExists(label, property));
+  auto create_index = std::make_shared<plan::CreateIndex>(label, property);
+  SymbolTable symbol_table;
+  EXPECT_EQ(PullAll(create_index, *dba, symbol_table), 1);
+  EXPECT_TRUE(dba->LabelPropertyIndexExists(label, property));
+}

tests/unit/query_planner.cpp

@@ -82,6 +82,11 @@ class PlanChecker : public HierarchicalLogicalOperatorVisitor {
     // Ignore checking Once, it is implicitly at the end.
     return true;
   }
+
+  bool Visit(CreateIndex &op) override {
+    CheckOp(op);
+    return true;
+  }
 #undef PRE_VISIT
 
   std::list<BaseOpChecker *> checkers_;