mirror of https://gitee.com/bigwinds/arangodb
301 lines
11 KiB
C++
301 lines
11 KiB
C++
////////////////////////////////////////////////////////////////////////////////
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/// @brief Infrastructure for RangeInfo
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///
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/// @file arangod/Aql/RangeInfo.h
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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 not James
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/// @author Copyright 2014, triagens GmbH, Cologne, Germany
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////////////////////////////////////////////////////////////////////////////////
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#include <Basics/Common.h>
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#include "Basics/JsonHelper.h"
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#include "Aql/RangeInfo.h"
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using namespace triagens::basics;
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using namespace triagens::aql;
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using Json = triagens::basics::Json;
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////////////////////////////////////////////////////////////////////////////////
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/// @brief 3-way comparison of the tightness of upper or lower constant
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/// RangeInfoBounds.
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/// Returns -1 if <left> is tighter than <right>, 1 if <right> is tighter than
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/// <left>, and 0 if the bounds are the same. The argument <lowhigh> should be
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/// -1 if we are comparing lower bounds and 1 if we are comparing upper bounds.
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///
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/// If <left> or <right> is a undefined, this indicates no bound.
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///
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/// If ~ is the comparison and (x,y), (z,t) are RangeInfoBounds (i.e. x,z are
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/// Json values, y,t are booleans) that we are comparing as lower bounds, then
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/// the following holds:
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///
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/// -1 x>z or (x=z, y=false, z=true)
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/// (x,y) ~ (z,t) = 0 x=z, y=t
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/// 1 z>x or (x=z, y=true, t=false)
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///
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/// as upper bounds:
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///
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/// -1 x<z or (x=z, y=false, z=true)
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/// (x,y) ~ (z,t) = 0 x=z, y=t
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/// 1 z<x or (x=z, y=true, t=false)
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///
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/// For example (x<2) is tighter than (x<3) and (x<=2). The bound (x<2) is
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/// represented as (2, false), and (x<=2) is (2, true), and so as upper bounds
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/// (2, false) ~ (2, true) = -1 indicating that (2,false)=(x<2) is tighter than
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/// (2, true)=(x<=2).
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////////////////////////////////////////////////////////////////////////////////
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static int CompareRangeInfoBound (RangeInfoBound const& left,
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RangeInfoBound const& right,
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int lowhigh) {
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if (! left.isDefined()) {
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return (right.isDefined() ? 1 : 0);
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}
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if (! right.isDefined()) {
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return -1;
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}
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int cmp = TRI_CompareValuesJson(left.bound().json(), right.bound().json());
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if (cmp == 0 && (left.inclusive() != right.inclusive())) {
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return (left.inclusive() ? 1 : -1);
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}
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return cmp * lowhigh;
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};
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////////////////////////////////////////////////////////////////////////////////
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/// @brief class RangeInfoBound
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////////////////////////////////////////////////////////////////////////////////
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////////////////////////////////////////////////////////////////////////////////
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/// @brief andCombineLowerBounds, changes the bound in *this and replaces
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/// it by the stronger bound of *this and that, interpreting both as lower
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/// bounds, this only works for constant bounds.
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////////////////////////////////////////////////////////////////////////////////
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void RangeInfoBound::andCombineLowerBounds (RangeInfoBound const& that) {
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if (CompareRangeInfoBound(that, *this, -1) == -1) {
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assign(that);
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}
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}
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////////////////////////////////////////////////////////////////////////////////
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/// @brief andCombineUpperBounds, changes the bound in *this and replaces
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/// it by the stronger bound of *this and that, interpreting both as upper
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/// bounds, this only works for constant bounds.
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////////////////////////////////////////////////////////////////////////////////
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void RangeInfoBound::andCombineUpperBounds (RangeInfoBound const& that) {
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if (CompareRangeInfoBound(that, *this, 1) == -1) {
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assign(that);
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}
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}
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////////////////////////////////////////////////////////////////////////////////
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/// @brief getExpressionAst, looks up or computes (if necessary) an AST
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/// for the variable bound, return nullptr for a constant bound, the new
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/// (if needed) nodes are registered with the ast
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////////////////////////////////////////////////////////////////////////////////
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AstNode const* RangeInfoBound::getExpressionAst (Ast* ast) const {
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if (_expressionAst != nullptr) {
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return _expressionAst;
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}
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if (_isConstant) {
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return nullptr;
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}
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_expressionAst = new AstNode(ast, _bound);
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return _expressionAst;
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}
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////////////////////////////////////////////////////////////////////////////////
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/// @brief class RangeInfo
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////////////////////////////////////////////////////////////////////////////////
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////////////////////////////////////////////////////////////////////////////////
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/// @brief constructor from JSON
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////////////////////////////////////////////////////////////////////////////////
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RangeInfo::RangeInfo (triagens::basics::Json const& json)
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: _var(basics::JsonHelper::checkAndGetStringValue(json.json(), "variable")),
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_attr(basics::JsonHelper::checkAndGetStringValue(json.json(), "attr")),
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_valid(basics::JsonHelper::checkAndGetBooleanValue(json.json(), "valid")),
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_defined(true),
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_equality(basics::JsonHelper::checkAndGetBooleanValue(json.json(), "equality")) {
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triagens::basics::Json jsonLowList = json.get("lows");
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if (! jsonLowList.isList()) {
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THROW_INTERNAL_ERROR("low attribute must be a list");
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}
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triagens::basics::Json jsonHighList = json.get("highs");
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if (! jsonHighList.isList()) {
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THROW_INTERNAL_ERROR("high attribute must be a list");
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}
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// If an exception is thrown from within these loops, then the
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// vectors _low and _high will be destroyed properly, so no
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// try/catch is needed.
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for (size_t i = 0; i < jsonLowList.size(); i++) {
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_lows.emplace_back(jsonLowList.at(static_cast<int>(i)));
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}
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for (size_t i = 0; i < jsonHighList.size(); i++) {
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_highs.emplace_back(jsonHighList.at(static_cast<int>(i)));
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}
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_lowConst.assign(json.get("lowConst"));
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_highConst.assign(json.get("highConst"));
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}
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////////////////////////////////////////////////////////////////////////////////
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/// @brief toJson for a RangeInfo
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////////////////////////////////////////////////////////////////////////////////
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triagens::basics::Json RangeInfo::toJson () const {
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triagens::basics::Json item(basics::Json::Array);
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item("variable", triagens::basics::Json(_var))
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("attr", triagens::basics::Json(_attr))
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("lowConst", _lowConst.toJson())
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("highConst", _highConst.toJson());
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triagens::basics::Json lowList(triagens::basics::Json::List, _lows.size());
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for (auto l : _lows) {
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lowList(l.toJson());
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}
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item("lows", lowList);
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triagens::basics::Json highList(triagens::basics::Json::List, _highs.size());
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for (auto h : _highs) {
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highList(h.toJson());
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}
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item("highs", highList);
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item("valid", triagens::basics::Json(_valid));
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item("equality", triagens::basics::Json(_equality));
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return item;
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}
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////////////////////////////////////////////////////////////////////////////////
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/// @brief class RangesInfo
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////////////////////////////////////////////////////////////////////////////////
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////////////////////////////////////////////////////////////////////////////////
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/// @brief insert if there is no range corresponding to variable name <var>,
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/// and attribute <name>, and otherwise intersection with existing range
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////////////////////////////////////////////////////////////////////////////////
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void RangesInfo::insert (RangeInfo newRange) {
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TRI_ASSERT(newRange.isDefined());
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std::unordered_map<std::string, RangeInfo>* oldMap = find(newRange._var);
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if (oldMap == nullptr) {
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std::unordered_map<std::string, RangeInfo> newMap;
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newMap.insert(make_pair(newRange._attr, newRange));
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_ranges.insert(std::make_pair(newRange._var, newMap));
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return;
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}
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auto it = oldMap->find(newRange._attr);
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if (it == oldMap->end()) {
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oldMap->insert(make_pair(newRange._attr, newRange));
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return;
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}
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RangeInfo& oldRange((*it).second);
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oldRange.fuse(newRange);
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}
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////////////////////////////////////////////////////////////////////////////////
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///// @brief fuse, fuse two ranges, must be for the same variable and attribute
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////////////////////////////////////////////////////////////////////////////////
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void RangeInfo::fuse (RangeInfo const& that) {
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TRI_ASSERT(_var == that._var);
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TRI_ASSERT(_attr == that._attr);
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if (! isValid()) {
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// intersection of the empty set with any set is empty!
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return;
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}
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if (! that.isValid()) {
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// intersection of the empty set with any set is empty!
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invalidate();
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return;
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}
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// The following is a corner case for constant bounds:
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if (_equality && that._equality &&
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_lowConst.isDefined() && that._lowConst.isDefined()) {
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if (! TRI_CheckSameValueJson(_lowConst.bound().json(),
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that._lowConst.bound().json())) {
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invalidate();
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return;
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}
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}
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// First sort out the constant low bounds:
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_lowConst.andCombineLowerBounds(that._lowConst);
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// Simply append the variable ones:
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for (auto l : that._lows) {
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_lows.emplace_back(l);
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}
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// Sort out the constant high bounds:
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_highConst.andCombineUpperBounds(that._highConst);
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// Simply append the variable ones:
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for (auto h : that._highs) {
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_highs.emplace_back(h);
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}
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// If either range knows that it can be at most one value, then this is
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// enough:
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_equality |= that._equality;
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// check the new constant range bounds are valid:
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if (_lowConst.isDefined() && _highConst.isDefined()) {
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int cmp = TRI_CompareValuesJson(_lowConst.bound().json(),
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_highConst.bound().json());
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if (cmp == 1) {
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invalidate();
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return;
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}
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if (cmp == 0) {
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if (! (_lowConst.inclusive() && _highConst.inclusive()) ) {
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// range invalid
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invalidate();
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}
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else {
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_equality = true; // Can only be at most one value
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}
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}
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}
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}
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////////////////////////////////////////////////////////////////////////////////
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/// @brief insert if there is no range corresponding to variable name <var>,
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/// and attribute <name>, and otherwise intersection with existing range
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////////////////////////////////////////////////////////////////////////////////
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void RangesInfo::insert (std::string const& var,
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std::string const& name,
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RangeInfoBound low,
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RangeInfoBound high,
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bool equality) {
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insert(RangeInfo(var, name, low, high, equality));
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}
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