memgraph/src/query/v2/cypher_query_interpreter.cpp

// Copyright 2022 Memgraph Ltd.
//
// Use of this software is governed by the Business Source License
// included in the file licenses/BSL.txt; by using this file, you agree to be bound by the terms of the Business Source
// License, and you may not use this file except in compliance with the Business Source License.
//
// As of the Change Date specified in that file, in accordance with
// the Business Source License, use of this software will be governed
// by the Apache License, Version 2.0, included in the file
// licenses/APL.txt.

#include "query/v2/cypher_query_interpreter.hpp"
#include "query/v2/bindings/symbol_generator.hpp"
#include "query/v2/request_router.hpp"

// NOLINTNEXTLINE (cppcoreguidelines-avoid-non-const-global-variables)
DEFINE_HIDDEN_bool(query_cost_planner, true, "Use the cost-estimating query planner.");
// NOLINTNEXTLINE (cppcoreguidelines-avoid-non-const-global-variables)
DEFINE_VALIDATED_int32(query_plan_cache_ttl, 60, "Time to live for cached query plans, in seconds.",
                       FLAG_IN_RANGE(0, std::numeric_limits<int32_t>::max()));

namespace memgraph::query::v2 {
CachedPlan::CachedPlan(std::unique_ptr<LogicalPlan> plan) : plan_(std::move(plan)) {}

ParsedQuery ParseQuery(const std::string &query_string, const std::map<std::string, storage::v3::PropertyValue> &params,
                       utils::SkipList<QueryCacheEntry> *cache, const InterpreterConfig::Query &query_config) {
  // Strip the query for caching purposes. The process of stripping a query
  // "normalizes" it by replacing any literals with new parameters. This
  // results in just the *structure* of the query being taken into account for
  // caching.
  frontend::StrippedQuery stripped_query{query_string};

  // Copy over the parameters that were introduced during stripping.
  Parameters parameters{stripped_query.literals()};

  // Check that all user-specified parameters are provided.
  for (const auto &param_pair : stripped_query.parameters()) {
    auto it = params.find(param_pair.second);

    if (it == params.end()) {
      throw query::v2::UnprovidedParameterError("Parameter ${} not provided.", param_pair.second);
    }

    parameters.Add(param_pair.first, it->second);
  }

  // Cache the query's AST if it isn't already.
  auto hash = stripped_query.hash();
  auto accessor = cache->access();
  auto it = accessor.find(hash);
  std::unique_ptr<memgraph::frontend::opencypher::Parser<>> parser;

  // Return a copy of both the AST storage and the query.
  CachedQuery result;
  bool is_cacheable = true;

  auto get_information_from_cache = [&](const auto &cached_query) {
    result.ast_storage.properties_ = cached_query.ast_storage.properties_;
    result.ast_storage.labels_ = cached_query.ast_storage.labels_;
    result.ast_storage.edge_types_ = cached_query.ast_storage.edge_types_;

    result.query = cached_query.query->Clone(&result.ast_storage);
    result.required_privileges = cached_query.required_privileges;
  };

  if (it == accessor.end()) {
    try {
      parser = std::make_unique<memgraph::frontend::opencypher::Parser<>>(stripped_query.query());
    } catch (const SyntaxException &e) {
      // There is a syntax exception in the stripped query. Re-run the parser
      // on the original query to get an appropriate error messsage.
      parser = std::make_unique<memgraph::frontend::opencypher::Parser<>>(query_string);

      // If an exception was not thrown here, the stripper messed something
      // up.
      LOG_FATAL("The stripped query can't be parsed, but the original can.");
    }

    // Convert the ANTLR4 parse tree into an AST.
    AstStorage ast_storage;
    expr::ParsingContext context{true};
    memgraph::expr::CypherMainVisitor visitor(context, &ast_storage);

    visitor.visit(parser->tree());

    if (visitor.GetQueryInfo().has_load_csv && !query_config.allow_load_csv) {
      throw utils::BasicException("Load CSV not allowed on this instance because it was disabled by a config.");
    }

    if (visitor.GetQueryInfo().is_cacheable) {
      CachedQuery cached_query{std::move(ast_storage), visitor.query(),
                               query::v2::GetRequiredPrivileges(visitor.query())};
      it = accessor.insert({hash, std::move(cached_query)}).first;

      get_information_from_cache(it->second);
    } else {
      result.ast_storage.properties_ = ast_storage.properties_;
      result.ast_storage.labels_ = ast_storage.labels_;
      result.ast_storage.edge_types_ = ast_storage.edge_types_;

      result.query = visitor.query()->Clone(&result.ast_storage);
      result.required_privileges = query::v2::GetRequiredPrivileges(visitor.query());

      is_cacheable = false;
    }
  } else {
    get_information_from_cache(it->second);
  }

  return ParsedQuery{query_string,
                     params,
                     std::move(parameters),
                     std::move(stripped_query),
                     std::move(result.ast_storage),
                     result.query,
                     std::move(result.required_privileges),
                     is_cacheable};
}

std::unique_ptr<LogicalPlan> MakeLogicalPlan(AstStorage ast_storage, CypherQuery *query, const Parameters &parameters,
                                             RequestRouterInterface *request_router,
                                             const std::vector<Identifier *> &predefined_identifiers) {
  auto vertex_counts = plan::MakeVertexCountCache(request_router);
  auto symbol_table = expr::MakeSymbolTable(query, predefined_identifiers);
  auto planning_context = plan::MakePlanningContext(&ast_storage, &symbol_table, query, &vertex_counts);
  auto [root, cost] = plan::MakeLogicalPlan(&planning_context, parameters, FLAGS_query_cost_planner);
  return std::make_unique<SingleNodeLogicalPlan>(std::move(root), cost, std::move(ast_storage),
                                                 std::move(symbol_table));
}

std::shared_ptr<CachedPlan> CypherQueryToPlan(uint64_t hash, AstStorage ast_storage, CypherQuery *query,
                                              const Parameters &parameters, utils::SkipList<PlanCacheEntry> *plan_cache,
                                              RequestRouterInterface *request_router,
                                              const std::vector<Identifier *> &predefined_identifiers) {
  std::optional<utils::SkipList<PlanCacheEntry>::Accessor> plan_cache_access;
  if (plan_cache) {
    plan_cache_access.emplace(plan_cache->access());
    auto it = plan_cache_access->find(hash);
    if (it != plan_cache_access->end()) {
      if (it->second->IsExpired()) {
        plan_cache_access->remove(hash);
      } else {
        return it->second;
      }
    }
  }

  auto plan = std::make_shared<CachedPlan>(
      MakeLogicalPlan(std::move(ast_storage), query, parameters, request_router, predefined_identifiers));
  if (plan_cache_access) {
    plan_cache_access->insert({hash, plan});
  }
  return plan;
}
}  // namespace memgraph::query::v2