mirror of https://gitee.com/bigwinds/arangodb
121 lines
3.6 KiB
C++
121 lines
3.6 KiB
C++
////////////////////////////////////////////////////////////////////////////////
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/// DISCLAIMER
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///
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/// Copyright 2019 ArangoDB 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 Yuriy Popov
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////////////////////////////////////////////////////////////////////////////////
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#include "Aql/Ast.h"
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#include "Aql/LateMaterializedOptimizerRulesCommon.h"
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using namespace arangodb::aql;
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namespace {
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// traverse the AST, using previsitor
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void traverseReadOnly(AstNode* node, AstNode* parentNode, size_t childNumber,
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std::function<bool(AstNode const*, AstNode*, size_t)> const& preVisitor) {
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if (node == nullptr) {
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return;
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}
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if (!preVisitor(node, parentNode, childNumber)) {
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return;
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}
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size_t const n = node->numMembers();
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for (size_t i = 0; i < n; ++i) {
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auto member = node->getMemberUnchecked(i);
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if (member != nullptr) {
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traverseReadOnly(member, node, i, preVisitor);
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}
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}
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}
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// traversal state
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struct TraversalState {
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Variable const* variable;
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latematerialized::NodeWithAttrs& nodeAttrs;
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bool optimize;
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bool wasAccess;
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};
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}
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// determines attributes referenced in an expression for the specified out variable
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bool latematerialized::getReferencedAttributes(AstNode* node,
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Variable const* variable,
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NodeWithAttrs& nodeAttrs) {
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TraversalState state{variable, nodeAttrs, true, false};
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auto preVisitor = [&state](AstNode const* node,
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AstNode* parentNode, size_t childNumber) {
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if (node == nullptr) {
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return false;
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}
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switch (node->type) {
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case NODE_TYPE_ATTRIBUTE_ACCESS:
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if (!state.wasAccess) {
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state.nodeAttrs.attrs.emplace_back(
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NodeWithAttrs::AttributeAndField{std::vector<arangodb::basics::AttributeName>{
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{std::string(node->getStringValue(), node->getStringLength()), false}}, {parentNode, childNumber, nullptr, 0}});
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state.wasAccess = true;
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} else {
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state.nodeAttrs.attrs.back().attr.emplace_back(std::string(node->getStringValue(), node->getStringLength()), false);
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}
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return true;
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case NODE_TYPE_REFERENCE: {
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// reference to a variable
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auto v = static_cast<Variable const*>(node->getData());
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if (v == state.variable) {
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if (!state.wasAccess) {
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// we haven't seen an attribute access directly before
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state.optimize = false;
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return false;
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}
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std::reverse(state.nodeAttrs.attrs.back().attr.begin(), state.nodeAttrs.attrs.back().attr.end());
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} else if (state.wasAccess) {
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state.nodeAttrs.attrs.pop_back();
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}
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// finish an attribute path
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state.wasAccess = false;
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return true;
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}
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default:
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break;
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}
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if (state.wasAccess) {
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// not appropriate node type
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state.wasAccess = false;
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state.optimize = false;
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return false;
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}
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return true;
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};
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traverseReadOnly(node, nullptr, 0, preVisitor);
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return state.optimize;
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}
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