mirror of https://gitee.com/bigwinds/arangodb
372 lines
12 KiB
C++
372 lines
12 KiB
C++
////////////////////////////////////////////////////////////////////////////////
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/// @brief IndexRangeNode
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///
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/// @file
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///
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/// DISCLAIMER
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///
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/// Copyright 2010-2014 triagens GmbH, Cologne, Germany
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///
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/// Licensed under the Apache License, Version 2.0 (the "License");
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/// you may not use this file except in compliance with the License.
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/// You may obtain a copy of the License at
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///
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/// http://www.apache.org/licenses/LICENSE-2.0
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///
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/// Unless required by applicable law or agreed to in writing, software
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/// distributed under the License is distributed on an "AS IS" BASIS,
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/// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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/// See the License for the specific language governing permissions and
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/// limitations under the License.
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///
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/// Copyright holder is triAGENS GmbH, Cologne, Germany
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///
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/// @author Max Neunhoeffer
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/// @author Copyright 2014, triagens GmbH, Cologne, Germany
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////////////////////////////////////////////////////////////////////////////////
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#include "Aql/IndexRangeNode.h"
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#include "Aql/Collection.h"
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#include "Aql/ExecutionPlan.h"
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#include "Aql/WalkerWorker.h"
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#include "Aql/Ast.h"
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#include "Basics/StringBuffer.h"
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using namespace std;
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using namespace triagens::basics;
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using namespace triagens::aql;
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// -----------------------------------------------------------------------------
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// --SECTION-- methods of IndexRangeNode
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// -----------------------------------------------------------------------------
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////////////////////////////////////////////////////////////////////////////////
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/// @brief toJson, for IndexRangeNode
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////////////////////////////////////////////////////////////////////////////////
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void IndexRangeNode::toJsonHelper (triagens::basics::Json& nodes,
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TRI_memory_zone_t* zone,
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bool verbose) const {
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triagens::basics::Json json(ExecutionNode::toJsonHelperGeneric(nodes, zone, verbose));
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// call base class method
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if (json.isEmpty()) {
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return;
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}
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// put together the range info . . .
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triagens::basics::Json ranges(triagens::basics::Json::Array, _ranges.size());
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for (auto const& x : _ranges) {
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triagens::basics::Json range(triagens::basics::Json::Array, x.size());
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for(auto const& y : x) {
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range.add(y.toJson());
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}
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ranges.add(range);
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}
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// Now put info about vocbase and cid in there
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json("database", triagens::basics::Json(_vocbase->_name))
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("collection", triagens::basics::Json(_collection->getName()))
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("outVariable", _outVariable->toJson())
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("ranges", ranges);
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json("index", _index->toJson());
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json("reverse", triagens::basics::Json(_reverse));
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// And add it:
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nodes(json);
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}
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ExecutionNode* IndexRangeNode::clone (ExecutionPlan* plan,
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bool withDependencies,
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bool withProperties) const {
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std::vector<std::vector<RangeInfo>> ranges;
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for (size_t i = 0; i < _ranges.size(); i++){
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ranges.emplace_back(std::vector<RangeInfo>());
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for (auto const& x : _ranges.at(i)) {
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ranges.at(i).emplace_back(x);
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}
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}
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auto outVariable = _outVariable;
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if (withProperties) {
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outVariable = plan->getAst()->variables()->createVariable(outVariable);
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}
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auto c = new IndexRangeNode(plan, _id, _vocbase, _collection,
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outVariable, _index, ranges, _reverse);
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cloneHelper(c, plan, withDependencies, withProperties);
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return static_cast<ExecutionNode*>(c);
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}
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////////////////////////////////////////////////////////////////////////////////
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/// @brief constructor for IndexRangeNode from Json
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////////////////////////////////////////////////////////////////////////////////
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IndexRangeNode::IndexRangeNode (ExecutionPlan* plan,
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triagens::basics::Json const& json)
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: ExecutionNode(plan, json),
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_vocbase(plan->getAst()->query()->vocbase()),
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_collection(plan->getAst()->query()->collections()->get(JsonHelper::checkAndGetStringValue(json.json(), "collection"))),
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_outVariable(varFromJson(plan->getAst(), json, "outVariable")),
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_index(nullptr),
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_ranges(),
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_reverse(false) {
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triagens::basics::Json rangeArrayJson(TRI_UNKNOWN_MEM_ZONE, JsonHelper::checkAndGetArrayValue(json.json(), "ranges"));
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for (size_t i = 0; i < rangeArrayJson.size(); i++) { //loop over the ranges . . .
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_ranges.emplace_back();
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triagens::basics::Json rangeJson(rangeArrayJson.at(static_cast<int>(i)));
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for (size_t j = 0; j < rangeJson.size(); j++) {
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_ranges.at(i).emplace_back(rangeJson.at(static_cast<int>(j)));
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}
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}
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// now the index . . .
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// TODO the following could be a constructor method for
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// an Index object when these are actually used
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auto index = JsonHelper::checkAndGetObjectValue(json.json(), "index");
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auto iid = JsonHelper::checkAndGetStringValue(index, "id");
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_index = _collection->getIndex(iid);
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_reverse = JsonHelper::checkAndGetBooleanValue(json.json(), "reverse");
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if (_index == nullptr) {
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THROW_ARANGO_EXCEPTION_MESSAGE(TRI_ERROR_INTERNAL, "index not found");
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}
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}
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////////////////////////////////////////////////////////////////////////////////
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/// @brief the cost of an index range node is a multiple of the cost of
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/// its unique dependency
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////////////////////////////////////////////////////////////////////////////////
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double IndexRangeNode::estimateCost (size_t& nrItems) const {
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static double const EqualityReductionFactor = 100.0;
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size_t incoming = 0;
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double const dependencyCost = _dependencies.at(0)->getCost(incoming);
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size_t docCount = _collection->count();
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TRI_ASSERT(! _ranges.empty());
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if (_index->type == triagens::arango::Index::TRI_IDX_TYPE_PRIMARY_INDEX) {
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// always an equality lookup
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// selectivity of primary index is always 1
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nrItems = incoming * _ranges.size();
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return dependencyCost + nrItems;
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}
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if (_index->type == triagens::arango::Index::TRI_IDX_TYPE_EDGE_INDEX) {
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// always an equality lookup
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// check if the index can provide a selectivity estimate
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if (! estimateItemsWithIndexSelectivity(incoming, nrItems)) {
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// use hard-coded heuristic
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nrItems = incoming * _ranges.size() * docCount / static_cast<size_t>(EqualityReductionFactor);
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}
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nrItems = (std::max)(nrItems, static_cast<size_t>(1));
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return dependencyCost + nrItems;
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}
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if (_index->type == triagens::arango::Index::TRI_IDX_TYPE_HASH_INDEX) {
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// always an equality lookup
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// check if the index can provide a selectivity estimate
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if (! estimateItemsWithIndexSelectivity(incoming, nrItems)) {
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// use hard-coded heuristic
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if (_index->unique) {
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nrItems = incoming * _ranges.size();
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}
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else {
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double cost = static_cast<double>(docCount) * incoming * _ranges.size();
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// the more attributes are contained in the index, the more specific the lookup will be
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for (size_t i = 0; i < _ranges.at(0).size(); ++i) {
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cost /= EqualityReductionFactor;
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}
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nrItems = static_cast<size_t>(cost);
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}
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}
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nrItems = (std::max)(nrItems, static_cast<size_t>(1));
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// the more attributes an index matches, the better it is
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double matchLengthFactor = _ranges.at(0).size() * 0.01;
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// this is to prefer the hash index over skiplists if everything else is equal
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return dependencyCost + ((static_cast<double>(nrItems) - matchLengthFactor) * 0.9999995);
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}
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if (_index->type == triagens::arango::Index::TRI_IDX_TYPE_SKIPLIST_INDEX) {
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auto const count = _ranges.at(0).size();
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if (count == 0) {
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// no ranges? so this is unlimited -> has to be more expensive
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nrItems = incoming * docCount;
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return dependencyCost + nrItems;
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}
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if (_index->unique) {
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bool allEquality = true;
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for (auto const& x : _ranges) {
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// check if we are using all indexed attributes in the query
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if (x.size() != _index->fields.size()) {
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allEquality = false;
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break;
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}
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// check if this is an equality comparison
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if (x.empty() || ! x.back().is1ValueRangeInfo()) {
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allEquality = false;
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break;
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}
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}
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if (allEquality) {
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// unique index, all attributes compared using eq (==) operator
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nrItems = incoming * _ranges.size();
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return dependencyCost + nrItems;
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}
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}
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// build a total cost for the index usage by peeking into all ranges
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double totalCost = 0.0;
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for (auto const& x : _ranges) {
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double cost = static_cast<double>(docCount) * incoming;
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for (auto const& y : x) { //only doing the 1-d case so far
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if (y.is1ValueRangeInfo()) {
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// equality lookup
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cost /= EqualityReductionFactor;
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continue;
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}
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bool hasLowerBound = false;
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bool hasUpperBound = false;
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if (y._lowConst.isDefined() || y._lows.size() > 0) {
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hasLowerBound = true;
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}
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if (y._highConst.isDefined() || y._highs.size() > 0) {
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hasUpperBound = true;
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}
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if (hasLowerBound && hasUpperBound) {
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// both lower and upper bounds defined
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cost /= 10.0;
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}
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else if (hasLowerBound || hasUpperBound) {
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// either only low or high bound defined
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cost /= 2.0;
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}
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// each bound (const and dynamic) counts!
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size_t const numBounds = y._lows.size() +
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y._highs.size() +
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(y._lowConst.isDefined() ? 1 : 0) +
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(y._highConst.isDefined() ? 1 : 0);
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for (size_t j = 0; j < numBounds; ++j) {
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// each dynamic bound again reduces the cost
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cost *= 0.95;
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}
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}
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totalCost += cost;
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}
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totalCost = static_cast<double>((std::max)(static_cast<size_t>(totalCost), static_cast<size_t>(1)));
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nrItems = static_cast<size_t>(totalCost);
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return dependencyCost + totalCost;
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}
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// no index
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nrItems = incoming * docCount;
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return dependencyCost + nrItems;
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}
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////////////////////////////////////////////////////////////////////////////////
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/// @brief getVariablesUsedHere, returning a vector
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////////////////////////////////////////////////////////////////////////////////
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std::vector<Variable const*> IndexRangeNode::getVariablesUsedHere () const {
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std::unordered_set<Variable const*> s;
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// actual work is done by that method
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getVariablesUsedHere(s);
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// copy result into vector
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std::vector<Variable const*> v;
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v.reserve(s.size());
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for (auto const& vv : s) {
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v.emplace_back(const_cast<Variable*>(vv));
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}
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return v;
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}
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////////////////////////////////////////////////////////////////////////////////
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/// @brief getVariablesUsedHere, modifying the set in-place
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////////////////////////////////////////////////////////////////////////////////
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void IndexRangeNode::getVariablesUsedHere (std::unordered_set<Variable const*>& vars) const {
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for (auto const& x : _ranges) {
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for (RangeInfo const& y : x) {
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for (RangeInfoBound const& z : y._lows) {
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AstNode const* a = z.getExpressionAst(_plan->getAst());
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Ast::getReferencedVariables(a, vars);
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}
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for (RangeInfoBound const& z : y._highs) {
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AstNode const* a = z.getExpressionAst(_plan->getAst());
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Ast::getReferencedVariables(a, vars);
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}
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}
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}
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}
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// -----------------------------------------------------------------------------
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// --SECTION-- private methods
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// -----------------------------------------------------------------------------
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////////////////////////////////////////////////////////////////////////////////
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/// @brief provide an estimate for the number of items, using the index
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/// selectivity info (if present)
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////////////////////////////////////////////////////////////////////////////////
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bool IndexRangeNode::estimateItemsWithIndexSelectivity (size_t incoming,
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size_t& nrItems) const {
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// check if the index can provide a selectivity estimate
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if (! _index->hasSelectivityEstimate()) {
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return false;
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}
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// use index selectivity estimate
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double estimate = _index->selectivityEstimate();
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if (estimate <= 0.0) {
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// avoid DIV0
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return false;
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}
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nrItems = static_cast<size_t>(incoming * _ranges.size() * (1.0 / estimate));
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return true;
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}
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// Local Variables:
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// mode: outline-minor
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// outline-regexp: "^\\(/// @brief\\|/// {@inheritDoc}\\|/// @addtogroup\\|// --SECTION--\\|/// @\\}\\)"
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// End:
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