mirror of https://github.com/mongodb/mongo
42 lines
1.8 KiB
Python
42 lines
1.8 KiB
Python
# Copyright (C) 2022-present MongoDB, Inc.
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#
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# This program is free software: you can redistribute it and/or modify
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# it under the terms of the Server Side Public License, version 1,
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# as published by MongoDB, Inc.
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#
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# Server Side Public License for more details.
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#
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# You should have received a copy of the Server Side Public License
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# along with this program. If not, see
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# <http://www.mongodb.com/licensing/server-side-public-license>.
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#
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# As a special exception, the copyright holders give permission to link the
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# code of portions of this program with the OpenSSL library under certain
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# conditions as described in each individual source file and distribute
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# linked combinations including the program with the OpenSSL library. You
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# must comply with the Server Side Public License in all respects for
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# all of the code used other than as permitted herein. If you modify file(s)
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# with this exception, you may extend this exception to your version of the
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# file(s), but you are not obligated to do so. If you do not wish to do so,
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# delete this exception statement from your version. If you delete this
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# exception statement from all source files in the program, then also delete
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# it in the license file.
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#
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"""
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Returns a preorder traversal (node, child 1...child n) of the QSN/execution tree
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For example, a query with an OR over 3 indices could turn into a tree rooted with a FETCH,
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who has a single OR child, which in turn has 3 index scan children.
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This would return a preorder of [FETCH, OR, IXSCAN1, IXSCAN2, IXSCAN3].
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"""
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def preorder(node):
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res = [node]
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for child in node.children:
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res += preorder(child)
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return res
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