arangodb/arangod/Aql/IndexNode.cpp

////////////////////////////////////////////////////////////////////////////////
/// DISCLAIMER
///
/// Copyright 2014-2016 ArangoDB GmbH, Cologne, Germany
/// Copyright 2004-2014 triAGENS GmbH, Cologne, Germany
///
/// Licensed under the Apache License, Version 2.0 (the "License");
/// you may not use this file except in compliance with the License.
/// You may obtain a copy of the License at
///
///     http://www.apache.org/licenses/LICENSE-2.0
///
/// Unless required by applicable law or agreed to in writing, software
/// distributed under the License is distributed on an "AS IS" BASIS,
/// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
/// See the License for the specific language governing permissions and
/// limitations under the License.
///
/// Copyright holder is ArangoDB GmbH, Cologne, Germany
///
/// @author Michael Hackstein
////////////////////////////////////////////////////////////////////////////////

#include "IndexNode.h"
#include "Aql/Ast.h"
#include "Aql/ClusterNodes.h"
#include "Aql/Collection.h"
#include "Aql/Condition.h"
#include "Aql/ExecutionPlan.h"
#include "Aql/Index.h"

using namespace triagens::aql;

using JsonHelper = triagens::basics::JsonHelper;

////////////////////////////////////////////////////////////////////////////////
/// @brief toJson, for IndexNode
////////////////////////////////////////////////////////////////////////////////

void IndexNode::toJsonHelper(triagens::basics::Json& nodes,
                             TRI_memory_zone_t* zone, bool verbose) const {
  triagens::basics::Json json(
      ExecutionNode::toJsonHelperGeneric(nodes, zone, verbose));
  // call base class method

  if (json.isEmpty()) {
    return;
  }

  // Now put info about vocbase and cid in there
  json("database", triagens::basics::Json(_vocbase->_name))(
      "collection", triagens::basics::Json(_collection->getName()))(
      "outVariable", _outVariable->toJson());

  triagens::basics::Json indexes(triagens::basics::Json::Array,
                                 _indexes.size());
  for (auto& index : _indexes) {
    indexes.add(index->toJson());
  }

  json("indexes", indexes);
  json("condition", _condition->toJson(TRI_UNKNOWN_MEM_ZONE, verbose));
  json("reverse", triagens::basics::Json(_reverse));

  // And add it:
  nodes(json);
}

ExecutionNode* IndexNode::clone(ExecutionPlan* plan, bool withDependencies,
                                bool withProperties) const {
  auto outVariable = _outVariable;

  if (withProperties) {
    outVariable = plan->getAst()->variables()->createVariable(outVariable);
  }

  auto c = new IndexNode(plan, _id, _vocbase, _collection, outVariable,
                         _indexes, _condition->clone(), _reverse);

  cloneHelper(c, plan, withDependencies, withProperties);

  return static_cast<ExecutionNode*>(c);
}

////////////////////////////////////////////////////////////////////////////////
/// @brief constructor for IndexNode from Json
////////////////////////////////////////////////////////////////////////////////

IndexNode::IndexNode(ExecutionPlan* plan, triagens::basics::Json const& json)
    : ExecutionNode(plan, json),
      _vocbase(plan->getAst()->query()->vocbase()),
      _collection(plan->getAst()->query()->collections()->get(
          JsonHelper::checkAndGetStringValue(json.json(), "collection"))),
      _outVariable(varFromJson(plan->getAst(), json, "outVariable")),
      _indexes(),
      _condition(nullptr),
      _reverse(JsonHelper::checkAndGetBooleanValue(json.json(), "reverse")) {
  auto indexes = JsonHelper::checkAndGetArrayValue(json.json(), "indexes");

  TRI_ASSERT(TRI_IsArrayJson(indexes));
  size_t length = TRI_LengthArrayJson(indexes);
  _indexes.reserve(length);

  for (size_t i = 0; i < length; ++i) {
    auto iid = JsonHelper::checkAndGetStringValue(
        TRI_LookupArrayJson(indexes, i), "id");
    auto index = _collection->getIndex(iid);

    if (index == nullptr) {
      THROW_ARANGO_EXCEPTION_MESSAGE(TRI_ERROR_INTERNAL, "index not found");
    }

    _indexes.emplace_back(index);
  }

  TRI_json_t const* condition =
      JsonHelper::checkAndGetObjectValue(json.json(), "condition");

  triagens::basics::Json conditionJson(TRI_UNKNOWN_MEM_ZONE, condition,
                                       triagens::basics::Json::NOFREE);
  _condition = Condition::fromJson(plan, conditionJson);

  TRI_ASSERT(_condition != nullptr);
}

////////////////////////////////////////////////////////////////////////////////
/// @brief destroy the IndexNode
////////////////////////////////////////////////////////////////////////////////

IndexNode::~IndexNode() { delete _condition; }

////////////////////////////////////////////////////////////////////////////////
/// @brief the cost of an index node is a multiple of the cost of
/// its unique dependency
////////////////////////////////////////////////////////////////////////////////

double IndexNode::estimateCost(size_t& nrItems) const {
  size_t incoming = 0;
  double const dependencyCost = _dependencies.at(0)->getCost(incoming);
  size_t const itemsInCollection = _collection->count();
  size_t totalItems = 0;
  double totalCost = 0.0;

  auto root = _condition->root();

  for (size_t i = 0; i < _indexes.size(); ++i) {
    double estimatedCost = 0.0;
    size_t estimatedItems = 0;

    triagens::aql::AstNode const* condition;
    if (root == nullptr || root->numMembers() <= i) {
      condition = nullptr;
    } else {
      condition = root->getMember(i);
    }

    if (condition != nullptr &&
        _indexes[i]->supportsFilterCondition(condition, _outVariable,
                                             itemsInCollection, estimatedItems,
                                             estimatedCost)) {
      totalItems += estimatedItems;
      totalCost += estimatedCost;
    } else {
      totalItems += itemsInCollection;
      totalCost += static_cast<double>(itemsInCollection);
    }
  }

  nrItems = incoming * totalItems;
  return dependencyCost + incoming * totalCost;
}

////////////////////////////////////////////////////////////////////////////////
/// @brief getVariablesUsedHere, returning a vector
////////////////////////////////////////////////////////////////////////////////

std::vector<Variable const*> IndexNode::getVariablesUsedHere() const {
  std::unordered_set<Variable const*> s;
  // actual work is done by that method
  getVariablesUsedHere(s);

  // copy result into vector
  std::vector<Variable const*> v;
  v.reserve(s.size());

  for (auto const& vv : s) {
    v.emplace_back(const_cast<Variable*>(vv));
  }
  return v;
}

////////////////////////////////////////////////////////////////////////////////
/// @brief getVariablesUsedHere, modifying the set in-place
////////////////////////////////////////////////////////////////////////////////

void IndexNode::getVariablesUsedHere(
    std::unordered_set<Variable const*>& vars) const {
  Ast::getReferencedVariables(_condition->root(), vars);

  vars.erase(_outVariable);
}