51 lines
1.1 KiB
MySQL
51 lines
1.1 KiB
MySQL
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-- SPDX-FileCopyrightText: 2024 Simon Bruder <simon@sbruder.de>
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--
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-- SPDX-License-Identifier: AGPL-3.0-or-later
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ALTER TABLE items
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ADD parent UUID REFERENCES items(id);
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CREATE RECURSIVE VIEW item_tree (id, parents) AS (
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SELECT id, ARRAY[]::UUID[] AS parents FROM items WHERE parent IS NULL
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UNION
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SELECT items.id, item_tree.parents || items.parent FROM items, item_tree WHERE items.parent = item_tree.id
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);
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CREATE FUNCTION check_item_cycle()
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RETURNS TRIGGER AS $$
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BEGIN
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IF NEW.parent IS NULL THEN
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RETURN NEW;
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END IF;
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IF NEW.id = NEW.parent THEN
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RAISE EXCEPTION 'Cycle detected';
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END IF;
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IF (WITH RECURSIVE cte AS (
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SELECT id, parent
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FROM items
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WHERE id = NEW.parent
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UNION
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SELECT items.id, items.parent
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FROM items, cte
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WHERE items.id = cte.parent
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)
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SELECT 1
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FROM cte
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WHERE parent = NEW.id
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LIMIT 1) THEN
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RAISE EXCEPTION 'Cycle detected';
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END IF;
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RETURN NEW;
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END;
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$$ LANGUAGE plpgsql;
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CREATE TRIGGER prevent_item_cycle
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BEFORE INSERT OR UPDATE ON items
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FOR EACH ROW
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EXECUTE FUNCTION check_item_cycle();
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