Query::Plan::Expand with preceeding optional bug fix
Summary: This diff contains a bug fix for the expansion operators that are currently on dev. More importantly, it proposes end-to-end testing for edge-cases for which it's a pain to write single-phase tests. In my opinion this is OK, you're all reviewers so you can comment. The test relies on left-to-right query execution. We need this guarantee in tests like this. I propose renaming "RuleBasedPlanner" to "LeftToRightPlanner" to make this explicit. As Teon is not here at the moment, will make this a task/discussion. Reviewers: buda, mislav.bradac, teon.banek, lion Reviewed By: mislav.bradac Subscribers: mferencevic, pullbot Differential Revision: https://phabricator.memgraph.io/D626
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florijan
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@ -478,35 +478,39 @@ void SwitchAccessor(TAccessor &accessor, GraphView graph_view) {
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bool Expand::ExpandCursor::InitEdges(Frame &frame,
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const SymbolTable &symbol_table) {
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if (!input_cursor_->Pull(frame, symbol_table)) return false;
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// Input Vertex could be null if it is created by a failed optional match. In
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// those cases we skip that input pull and continue with the next.
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while (true) {
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if (!input_cursor_->Pull(frame, symbol_table)) return false;
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TypedValue &vertex_value = frame[self_.input_symbol_];
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TypedValue &vertex_value = frame[self_.input_symbol_];
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// Vertex could be null if it is created by a failed optional match, in such a
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// case we should stop expanding.
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if (vertex_value.IsNull()) return false;
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ExpectType(self_.input_symbol_, vertex_value, TypedValue::Type::Vertex);
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auto &vertex = vertex_value.Value<VertexAccessor>();
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SwitchAccessor(vertex, self_.graph_view_);
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// Null check due to possible failed optional match.
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if (vertex_value.IsNull()) continue;
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auto direction = self_.direction_;
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if (direction == EdgeAtom::Direction::IN ||
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direction == EdgeAtom::Direction::BOTH) {
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in_edges_ = std::make_unique<InEdgeT>(vertex.in());
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in_edges_it_ = std::make_unique<InEdgeIteratorT>(in_edges_->begin());
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ExpectType(self_.input_symbol_, vertex_value, TypedValue::Type::Vertex);
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auto &vertex = vertex_value.Value<VertexAccessor>();
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SwitchAccessor(vertex, self_.graph_view_);
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auto direction = self_.direction_;
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if (direction == EdgeAtom::Direction::IN ||
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direction == EdgeAtom::Direction::BOTH) {
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in_edges_ = std::make_unique<InEdgeT>(vertex.in());
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in_edges_it_ = std::make_unique<InEdgeIteratorT>(in_edges_->begin());
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}
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if (direction == EdgeAtom::Direction::OUT ||
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direction == EdgeAtom::Direction::BOTH) {
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out_edges_ = std::make_unique<InEdgeT>(vertex.out());
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out_edges_it_ = std::make_unique<InEdgeIteratorT>(out_edges_->begin());
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}
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// TODO add support for Front and Back expansion (when QueryPlanner
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// will need it). For now only Back expansion (left to right) is
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// supported
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// TODO add support for named paths
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return true;
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}
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if (direction == EdgeAtom::Direction::OUT ||
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direction == EdgeAtom::Direction::BOTH) {
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out_edges_ = std::make_unique<InEdgeT>(vertex.out());
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out_edges_it_ = std::make_unique<InEdgeIteratorT>(out_edges_->begin());
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}
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// TODO add support for Front and Back expansion (when QueryPlanner
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// will need it). For now only Back expansion (left to right) is
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// supported
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// TODO add support for named paths
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return true;
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}
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bool Expand::ExpandCursor::PullNode(const EdgeAccessor &new_edge,
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@ -666,41 +670,45 @@ class ExpandVariableCursor : public Cursor {
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* is exhausted.
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*/
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bool PullInput(Frame &frame, const SymbolTable &symbol_table) {
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if (!input_cursor_->Pull(frame, symbol_table)) return false;
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// Input Vertex could be null if it is created by a failed optional match.
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// In those cases we skip that input pull and continue with the next.
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while (true) {
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if (!input_cursor_->Pull(frame, symbol_table)) return false;
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TypedValue &vertex_value = frame[self_.input_symbol_];
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TypedValue &vertex_value = frame[self_.input_symbol_];
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// Vertex could be null if it is created by a failed optional match, in
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// such a case we should stop expanding.
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if (vertex_value.IsNull()) return false;
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ExpectType(self_.input_symbol_, vertex_value, TypedValue::Type::Vertex);
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auto &vertex = vertex_value.Value<VertexAccessor>();
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SwitchAccessor(vertex, self_.graph_view_);
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// Null check due to possible failed optional match.
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if (vertex_value.IsNull()) continue;
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// evaluate the upper and lower bounds
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ExpressionEvaluator evaluator(frame, symbol_table, db_);
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auto calc_bound = [this, &evaluator](auto &bound) {
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auto value = EvaluateInt(evaluator, bound, "Variable expansion bound");
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if (value < 0)
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throw QueryRuntimeException(
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"Variable expansion bound must be positive or zero");
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return value;
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};
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lower_bound_ = self_.lower_bound_ ? calc_bound(self_.lower_bound_) : 1;
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upper_bound_ = self_.upper_bound_ ? calc_bound(self_.upper_bound_)
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: std::numeric_limits<int64_t>::max();
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if (upper_bound_ > 0) {
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ExpectType(self_.input_symbol_, vertex_value, TypedValue::Type::Vertex);
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auto &vertex = vertex_value.Value<VertexAccessor>();
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SwitchAccessor(vertex, self_.graph_view_);
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edges_.emplace_back(ExpandFromVertex(vertex, self_.direction_));
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edges_it_.emplace_back(edges_.back().begin());
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// Evaluate the upper and lower bounds.
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ExpressionEvaluator evaluator(frame, symbol_table, db_);
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auto calc_bound = [this, &evaluator](auto &bound) {
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auto value = EvaluateInt(evaluator, bound, "Variable expansion bound");
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if (value < 0)
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throw QueryRuntimeException(
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"Variable expansion bound must be positive or zero");
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return value;
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};
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lower_bound_ = self_.lower_bound_ ? calc_bound(self_.lower_bound_) : 1;
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upper_bound_ = self_.upper_bound_ ? calc_bound(self_.upper_bound_)
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: std::numeric_limits<int64_t>::max();
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if (upper_bound_ > 0) {
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SwitchAccessor(vertex, self_.graph_view_);
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edges_.emplace_back(ExpandFromVertex(vertex, self_.direction_));
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edges_it_.emplace_back(edges_.back().begin());
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}
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// reset the frame value to an empty edge list
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if (!self_.existing_edge_)
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frame[self_.edge_symbol_] = std::vector<TypedValue>();
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return true;
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}
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// reset the frame value to an empty edge list
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if (!self_.existing_edge_)
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frame[self_.edge_symbol_] = std::vector<TypedValue>();
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return true;
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}
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/**
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61
tests/unit/query_plan_edge_cases.cpp
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61
tests/unit/query_plan_edge_cases.cpp
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@ -0,0 +1,61 @@
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// tests in this suite deal with edge cases in logical operator behavior
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// that's not easily testable with single-phase testing. instead, for
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// easy testing and latter readability they are tested end-to-end.
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#include "gmock/gmock.h"
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#include "gtest/gtest.h"
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#include "communication/result_stream_faker.hpp"
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#include "database/dbms.hpp"
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#include "query/interpreter.hpp"
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class QueryExecution : public testing::Test {
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protected:
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Dbms dbms_;
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std::unique_ptr<GraphDbAccessor> db_ = dbms_.active();
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/** Commits the current transaction and refreshes the db_
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* variable to hold a new accessor with a new transaction */
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void Commit() {
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db_->commit();
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auto next_db = dbms_.active();
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db_.swap(next_db);
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}
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/** Executes the query and returns the results.
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* Does NOT commit the transaction */
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auto Execute(const std::string &query) {
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ResultStreamFaker results;
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query::Interpreter().Interpret(query, *db_, results, {});
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return results.GetResults();
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}
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};
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TEST_F(QueryExecution, MissingOptionalIntoExpand) {
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// validating bug where expanding from Null (due to a preceeding optional
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// match) exhausts the expansion cursor, even if it's input is still not
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// exhausted
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Execute(
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"CREATE (a:Person {id: 1}), (b:Person "
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"{id:2})-[:Has]->(:Dog)-[:Likes]->(:Food )");
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Commit();
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ASSERT_EQ(Execute("MATCH (n) RETURN n").size(), 4);
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auto Exec = [this](bool desc, bool variable) {
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// this test depends on left-to-right query planning
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FLAGS_query_cost_planner = false;
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return Execute(std::string("MATCH (p:Person) WITH p ORDER BY p.id ") +
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(desc ? "DESC " : "") +
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"OPTIONAL MATCH (p)-->(d:Dog) WITH p, d "
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"MATCH (d)-" + (variable ? "[*1]" : "") + "->(f:Food) "
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"RETURN p, d, f")
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.size();
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};
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EXPECT_EQ(Exec(false, false), 1);
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EXPECT_EQ(Exec(true, false), 1);
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EXPECT_EQ(Exec(false, true), 1);
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EXPECT_EQ(Exec(true, true), 1);
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// TODO test/fix ExpandBreadthFirst once it's operator lands
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}
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