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#pragma once
#include <Interpreters/ActionsDAG.h>
namespace DB
{
/// This structure stores a node mapping from one DAG to another.
/// The rule is following:
/// * Input nodes are mapped by name.
/// * Function is mapped to function if all children are mapped and function names are same.
/// * Alias is mapped to it's children mapping.
/// * Monotonic function can be mapped to it's children mapping if direct mapping does not exist.
/// In this case, information about monotonicity is filled.
/// * Mapped node is nullptr if there is no mapping found.
///
/// Overall, directly mapped nodes represent equal calculations.
/// Notes:
/// * Mapped DAG can contain many nodes which represent the same calculation.
/// In this case mapping is ambiguous and only one node is mapped.
/// * Aliases for mapped DAG are not supported.
/// DAG for PK does not contain aliases and ambiguous nodes.
struct MatchedTrees
{
/// Monotonicity is calculated for monotonic functions chain.
/// Chain is not strict if there is any non-strict monotonic function.
struct Monotonicity
{
int direction = 1;
bool strict = true;
};
struct Match
{
const ActionsDAG::Node * node = nullptr;
std::optional<Monotonicity> monotonicity;
};
using Matches = std::unordered_map<const ActionsDAG::Node *, Match>;
};
MatchedTrees::Matches matchTrees(const ActionsDAG & inner_dag, const ActionsDAG & outer_dag, bool check_monotonicity = true);
}
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