/* Copyright (c) 2020, 2021, Oracle and/or its affiliates.

This program is free software; you can redistribute it and/or modify

it under the terms of the GNU General Public License, version 2.0,

as published by the Free Software Foundation.

This program is also distributed with certain software (including

but not limited to OpenSSL) that is licensed under separate terms,

as designated in a particular file or component or in included license

documentation. The authors of MySQL hereby grant you an additional

permission to link the program and your derivative works with the

separately licensed software that they have included with MySQL.

This program is distributed in the hope that it will be useful,

but WITHOUT ANY WARRANTY; without even the implied warranty of

MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the

GNU General Public License, version 2.0, for more details.

You should have received a copy of the GNU General Public License

along with this program; if not, write to the Free Software

Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA */

#include "sql/join_optimizer/hypergraph.h"

#include "sql/join_optimizer/bit_utils.h"

namespace hypergraph {

void Hypergraph::AddNode() { nodes.emplace_back(); }

void Hypergraph::AddEdge(NodeMap left, NodeMap right) {

// Clone the edge, so that on any node, it is guaranteed to be on the

// “left” side of the edge. This saves a lot of repetitive code and

// branch misprediction; the microbenchmarks are up 10–30%.

assert(left != 0);

assert(right != 0);

edges.emplace_back(Hyperedge{left, right});

edges.emplace_back(Hyperedge{right, left});

size_t left_first_idx = edges.size() - 2;

size_t right_first_idx = edges.size() - 1;

if (IsSingleBitSet(left) && IsSingleBitSet(right)) {

size_t left_node = *BitsSetIn(left).begin();

size_t right_node = *BitsSetIn(right).begin();

nodes[left_node].simple_neighborhood |= right;

nodes[right_node].simple_neighborhood |= left;

nodes[left_node].simple_edges.push_back(left_first_idx);

nodes[right_node].simple_edges.push_back(right_first_idx);

} else {

for (size_t left_node : BitsSetIn(left)) {

assert(left_node < nodes.size());

nodes[left_node].complex_edges.push_back(left_first_idx);

}

for (size_t right_node : BitsSetIn(right)) {

assert(right_node < nodes.size());

nodes[right_node].complex_edges.push_back(right_first_idx);

}

}

}

} // namespace hypergraph