mirror of https://gitee.com/bigwinds/arangodb
265 lines
10 KiB
C++
265 lines
10 KiB
C++
////////////////////////////////////////////////////////////////////////////////
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/// @brief simple index attribute matcher
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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 2014 ArangoDB GmbH, Cologne, Germany
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/// Copyright 2004-2014 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 ArangoDB GmbH, Cologne, Germany
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///
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/// @author Jan Steemann
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/// @author Copyright 2014, ArangoDB GmbH, Cologne, Germany
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/// @author Copyright 2011-2013, triAGENS GmbH, Cologne, Germany
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////////////////////////////////////////////////////////////////////////////////
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#ifndef ARANGODB_INDEXES_SIMPLE_ATTRIBUTE_EQUALITY_MATCHER_H
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#define ARANGODB_INDEXES_SIMPLE_ATTRIBUTE_EQUALITY_MATCHER_H 1
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#include "Basics/Common.h"
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#include "Aql/Ast.h"
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#include "Aql/AstNode.h"
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#include "Aql/Variable.h"
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#include "Basics/AttributeNameParser.h"
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#include "Indexes/Index.h"
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#include "VocBase/vocbase.h"
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namespace triagens {
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namespace arango {
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// -----------------------------------------------------------------------------
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// --SECTION-- class SimpleAttributeEqualityMatcher
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// -----------------------------------------------------------------------------
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class SimpleAttributeEqualityMatcher {
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// -----------------------------------------------------------------------------
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// --SECTION-- constructors / destructors
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// -----------------------------------------------------------------------------
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public:
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SimpleAttributeEqualityMatcher (std::vector<std::vector<triagens::basics::AttributeName>> const& attributes)
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: _attributes(attributes) {
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}
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// -----------------------------------------------------------------------------
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// --SECTION-- public methods
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// -----------------------------------------------------------------------------
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public:
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////////////////////////////////////////////////////////////////////////////////
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/// @brief match a single of the attributes
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/// this is used for the primary index and the edge index
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////////////////////////////////////////////////////////////////////////////////
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inline bool matchOne (triagens::arango::Index const* index,
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triagens::aql::AstNode const* node,
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triagens::aql::Variable const* reference,
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double& estimatedCost) const {
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std::unordered_set<size_t> found;
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for (size_t i = 0; i < node->numMembers(); ++i) {
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auto op = node->getMember(i);
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if (op->type == triagens::aql::NODE_TYPE_OPERATOR_BINARY_EQ) {
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TRI_ASSERT(op->numMembers() == 2);
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if (accessFitsIndex(index, op->getMember(0), op->getMember(1), op, reference, found) ||
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accessFitsIndex(index, op->getMember(1), op->getMember(0), op, reference, found)) {
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// we can use the index
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return indexCosts(index, estimatedCost);
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}
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}
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else if (op->type == triagens::aql::NODE_TYPE_OPERATOR_BINARY_IN) {
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TRI_ASSERT(op->numMembers() == 2);
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if (accessFitsIndex(index, op->getMember(0), op->getMember(1), op, reference, found)) {
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// we can use the index
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return indexCosts(index, estimatedCost) * op->getMember(1)->numMembers();
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}
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}
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}
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estimatedCost = 1.0; // set to highest possible cost by default
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return false;
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}
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////////////////////////////////////////////////////////////////////////////////
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/// @brief match all of the attributes, in any order
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/// this is used for the hash index
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////////////////////////////////////////////////////////////////////////////////
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inline bool matchAll (triagens::arango::Index const* index,
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triagens::aql::AstNode const* node,
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triagens::aql::Variable const* reference,
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double& estimatedCost) const {
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std::unordered_set<size_t> found;
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size_t values = 0;
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for (size_t i = 0; i < node->numMembers(); ++i) {
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auto op = node->getMember(i);
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if (op->type == triagens::aql::NODE_TYPE_OPERATOR_BINARY_EQ) {
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TRI_ASSERT(op->numMembers() == 2);
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if (accessFitsIndex(index, op->getMember(0), op->getMember(1), op, reference, found) ||
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accessFitsIndex(index, op->getMember(1), op->getMember(0), op, reference, found)) {
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if (found.size() == _attributes.size()) {
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// got enough attributes
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break;
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}
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}
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}
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else if (op->type == triagens::aql::NODE_TYPE_OPERATOR_BINARY_IN) {
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TRI_ASSERT(op->numMembers() == 2);
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if (accessFitsIndex(index, op->getMember(0), op->getMember(1), op, reference, found)) {
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values += op->getMember(1)->numMembers();
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if (found.size() == _attributes.size()) {
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// got enough attributes
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break;
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}
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}
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}
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}
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if (found.size() == _attributes.size()) {
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// can only use this index if all index attributes are covered by the condition
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if (values == 0) {
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values = 1;
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}
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return indexCosts(index, estimatedCost) / static_cast<double>(index->fields().size()) * static_cast<double>(values);
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}
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estimatedCost = 1.0; // set to highest possible cost by default
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return false;
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}
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// -----------------------------------------------------------------------------
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// --SECTION-- private methods
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// -----------------------------------------------------------------------------
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private:
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////////////////////////////////////////////////////////////////////////////////
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/// @brief determine the costs of using this index
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/// costs returned are scaled from 0.0 to 1.0, with 0.0 being the lowest cost
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////////////////////////////////////////////////////////////////////////////////
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bool indexCosts (triagens::arango::Index const* index,
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double& estimatedCost) const {
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if (index->unique()) {
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// index is unique, and the condition covers all attributes
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// now use a low value for the costs
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estimatedCost = std::numeric_limits<double>::epsilon();
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}
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else if (index->hasSelectivityEstimate()) {
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// use index selectivity estimate
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estimatedCost = 1.0 - index->selectivityEstimate();
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}
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else {
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// set to highest possible cost by default
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estimatedCost = 1.0;
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}
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// can use this index
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return true;
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}
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////////////////////////////////////////////////////////////////////////////////
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/// @brief whether or not the access fits
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////////////////////////////////////////////////////////////////////////////////
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bool accessFitsIndex (triagens::arango::Index const* index,
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triagens::aql::AstNode const* access,
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triagens::aql::AstNode const* other,
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triagens::aql::AstNode const* op,
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triagens::aql::Variable const* reference,
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std::unordered_set<size_t>& found) const {
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if (! index->canUseConditionPart(access, other, op, reference)) {
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return false;
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}
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if (access->type != triagens::aql::NODE_TYPE_ATTRIBUTE_ACCESS) {
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return false;
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}
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std::vector<std::string> fieldNames;
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while (access->type == triagens::aql::NODE_TYPE_ATTRIBUTE_ACCESS) {
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fieldNames.emplace_back(std::string(access->getStringValue(), access->getStringLength()));
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access = access->getMember(0);
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}
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if (access->type != triagens::aql::NODE_TYPE_REFERENCE) {
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return false;
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}
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if (access->getData() != reference) {
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// this access is not referencing this collection
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return false;
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}
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for (size_t i = 0; i < _attributes.size(); ++i) {
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if (_attributes[i].size() != fieldNames.size()) {
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// attribute path length differs
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continue;
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}
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bool match = true;
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for (size_t j = 0; j < _attributes[i].size(); ++j) {
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if (_attributes[i][j].shouldExpand ||
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_attributes[i][j].name != fieldNames[j]) {
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match = false;
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break;
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}
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}
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if (match) {
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// mark ith attribute as being covered
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found.emplace(i);
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return true;
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}
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}
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return false;
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}
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// -----------------------------------------------------------------------------
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// --SECTION-- private variables
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// -----------------------------------------------------------------------------
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private:
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////////////////////////////////////////////////////////////////////////////////
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/// @brief array of attributes used for comparisons
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////////////////////////////////////////////////////////////////////////////////
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std::vector<std::vector<triagens::basics::AttributeName>> _attributes;
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};
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}
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}
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#endif
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// -----------------------------------------------------------------------------
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// --SECTION-- END-OF-FILE
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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}\\|/// @page\\|// --SECTION--\\|/// @\\}"
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// End:
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