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94 lines
2.4 KiB
C++
94 lines
2.4 KiB
C++
#pragma once
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#include <Parsers/IAST_fwd.h>
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#include <Parsers/ASTLiteral.h>
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#include <unordered_map>
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#include <vector>
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namespace DB
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{
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/*
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* Graph of relations between terms in constraints.
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* Allows to compare terms and get equal terms.
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*/
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class ComparisonGraph
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{
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public:
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ComparisonGraph(const std::vector<ASTPtr> & atomic_formulas);
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/// Works for string and num.
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/// For other -- only eq.
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enum class CompareResult
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{
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LESS,
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LESS_OR_EQUAL,
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EQUAL,
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GREATER_OR_EQUAL,
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GREATER,
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UNKNOWN,
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};
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CompareResult compare(const ASTPtr & left, const ASTPtr & right) const;
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std::vector<ASTPtr> getEqual(const ASTPtr & ast) const;
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std::optional<ASTPtr> getEqualConst(const ASTPtr & ast) const;
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/// Find constants less and greater.
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/// For int and double linear programming can be applied here.
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// TODO: implement
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//ASTPtr getMax(const ASTPtr &) const { return nullptr; } // sup
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//ASTPtr getMin(const ASTPtr &) const { return nullptr; } // inf
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private:
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/// strongly connected component
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struct EqualComponent
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{
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std::vector<ASTPtr> asts;
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};
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/// TODO: move to diff for int and double:
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/// LESS and LESS_OR_EQUAL with +const or 0 --- ok
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/// with -const --- not ok
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/// EQUAL is ok only for 0
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struct Edge
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{
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enum Type
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{
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LESS,
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LESS_OR_EQUAL,
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EQUAL,
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};
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Type type;
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size_t to;
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};
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struct Graph
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{
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struct ASTHash {
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size_t operator() (const IAST::Hash & hash) const {
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return hash.first;
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}
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};
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std::unordered_map<IAST::Hash, size_t, ASTHash> ast_hash_to_component;
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std::vector<EqualComponent> vertexes;
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std::vector<std::vector<Edge>> edges;
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};
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ASTPtr normalizeAtom(const ASTPtr & atom) const;
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Graph BuildGraphFromAstsGraph(const Graph & asts_graph) const;
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Graph reverseGraph(const Graph & asts_graph) const;
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void dfsOrder(const Graph & asts_graph, size_t v, std::vector<bool> & visited, std::vector<size_t> & order) const;
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void dfsComponents(
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const Graph & reversed_graph, size_t v, std::vector<size_t> & components, const size_t not_visited, const size_t component) const;
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std::pair<bool, bool> findPath(const size_t start, const size_t finish) const;
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Graph graph;
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};
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}
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