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Generate multiple plans and use the least costly one

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Summary:
This is a simple integration of multiple plan generation and cost
estimation. Each plan produced by VariableStartPlanner is cost estimated
and the best is used for execution.

Reviewers: florijan, mislav.bradac, buda

Reviewed By: florijan

Subscribers: pullbot

Differential Revision: https://phabricator.memgraph.io/D424
This commit is contained in:
Teon Banek 2017-06-05 12:44:18 +02:00
parent 666f8e1a93
commit b2c523b93a
1 changed files with 31 additions and 11 deletions
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42
src/query/interpreter.hpp
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@ -1,6 +1,7 @@
#pragma once
#include <ctime>
#include <limits>
#include "database/graph_db_accessor.hpp"
#include "query/context.hpp"
@ -40,13 +41,33 @@ void Interpret(const std::string &query, GraphDbAccessor &db_accessor,
high_level_tree->Accept(symbol_generator);
// high level tree -> logical plan
auto logical_plan = plan::MakeLogicalPlan<plan::RuleBasedPlanner>(
visitor.storage(), symbol_table, &db_accessor);
// cost estimation
plan::CostEstimator cost_estimator(db_accessor);
logical_plan->Accept(cost_estimator);
double query_plan_cost_estimation = cost_estimator.cost();
std::unique_ptr<plan::LogicalOperator> logical_plan;
double query_plan_cost_estimation = 0.0;
// TODO: Use gflags
bool FLAGS_query_cost_planner = true;
if (FLAGS_query_cost_planner) {
auto plans = plan::MakeLogicalPlan<plan::VariableStartPlanner>(
visitor.storage(), symbol_table, &db_accessor);
double min_cost = std::numeric_limits<double>::max();
for (auto &plan : plans) {
plan::CostEstimator estimator(db_accessor);
plan->Accept(estimator);
auto cost = estimator.cost();
if (!logical_plan || cost < min_cost) {
// We won't be iterating over plans anymore, so it's ok to invalidate
// unique_ptrs inside.
logical_plan = std::move(plan);
min_cost = cost;
}
}
query_plan_cost_estimation = min_cost;
} else {
logical_plan = plan::MakeLogicalPlan<plan::RuleBasedPlanner>(
visitor.storage(), symbol_table, &db_accessor);
plan::CostEstimator cost_estimator(db_accessor);
logical_plan->Accept(cost_estimator);
query_plan_cost_estimation = cost_estimator.cost();
}
// generate frame based on symbol table max_position
Frame frame(symbol_table.max_position());
@ -84,7 +105,7 @@ void Interpret(const std::string &query, GraphDbAccessor &db_accessor,
auto cursor = logical_plan->MakeCursor(db_accessor);
while (cursor->Pull(frame, symbol_table)) continue;
} else {
throw QueryRuntimeException("Unknown top level LogicalOp");
throw QueryRuntimeException("Unknown top level LogicalOperator");
}
clock_t execution_end_time = clock();
@ -100,11 +121,10 @@ void Interpret(const std::string &query, GraphDbAccessor &db_accessor,
summary["query_plan_execution_time"] =
time_second(planning_end_time, execution_end_time);
summary["query_cost_estimate"] = query_plan_cost_estimation;
//
// TODO set summary['type'] based on transaction metadata
// the type can't be determined based only on top level LogicalOp
// the type can't be determined based only on top level LogicalOperator
// (for example MATCH DELETE RETURN will have Produce as it's top)
// for now always se "rw" because something must be set, but it doesn't
// for now always use "rw" because something must be set, but it doesn't
// have to be correct (for Bolt clients)
summary["type"] = "rw";
stream.Summary(summary);