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experiment.sql
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experiment.sql
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CREATE SEQUENCE move_ops_seq;
CREATE EXTENSION IF NOT EXISTS "uuid-ossp";
CREATE TYPE unique_timestamp AS (
time timestamptz,
counter bigint,
id uuid
);
CREATE TABLE move_ops2 (
time unique_timestamp PRIMARY KEY DEFAULT (now(), nextval('move_ops_seq'), uuid_generate_v4()),
parent bigint NOT NULL,
name text NOT NULL,
child bigint NOT NULL,
valid boolean NOT NULL DEFAULT 'true'
);
CREATE INDEX ON move_ops (parent);
CREATE INDEX ON move_ops (child);
CREATE OR REPLACE VIEW tree AS
SELECT m1.parent AS parent, m1.name AS name, m1.child AS child
FROM move_ops AS m1
LEFT JOIN move_ops AS m2
ON m1.time < m2.time AND m1.child = m2.child AND m2.valid
WHERE m1.valid AND m2 IS NULL;
CREATE OR REPLACE FUNCTION ancestors_before(parent bigint, threshold unique_timestamp)
RETURNS TABLE(ancestor bigint) AS $$
WITH RECURSIVE ancestors(ancestor) AS (
VALUES (parent)
UNION
SELECT m1.parent FROM ancestors
JOIN move_ops AS m1
ON m1.child = ancestor AND m1.valid AND m1.time < threshold
LEFT JOIN move_ops AS m2
ON m2.child = ancestor AND m2.valid AND m2.time < threshold AND m1.time < m2.time
WHERE m2 IS NULL
)
SELECT * from ancestors
$$ LANGUAGE SQL;
CREATE OR REPLACE FUNCTION process_move() RETURNS trigger AS $$
DECLARE
move RECORD;
BEGIN
FOR move IN SELECT * FROM move_ops WHERE time >= NEW.time ORDER BY time FOR UPDATE LOOP
IF move.child IN (SELECT ancestors_before(move.parent, move.time)) THEN
RAISE NOTICE 'INVALID: %', move;
IF move.valid THEN
UPDATE move_ops SET valid = 'false' WHERE time = move.time;
END IF;
ELSE
RAISE NOTICE 'valid: %', move;
IF NOT move.valid THEN
UPDATE move_ops SET valid = 'true' WHERE time = move.time;
END IF;
END IF;
END LOOP;
RETURN NULL;
END;
$$ LANGUAGE plpgsql;
CREATE TRIGGER process_move AFTER INSERT ON move_ops
FOR EACH ROW EXECUTE FUNCTION process_move();
CREATE OR REPLACE VIEW tree_view AS
WITH RECURSIVE tree_view (node, path) AS (
VALUES(0::bigint, ARRAY[]::text[])
UNION ALL
SELECT tree.child, tree_view.path || tree.name
FROM tree_view JOIN tree ON tree_view.node = tree.parent
)
SELECT CASE
WHEN path = array[]::text[] THEN node::text
ELSE repeat('|- ', array_length(path, 1)) || path[array_length(path, 1)] || ': ' || node::text
END
FROM tree_view ORDER BY path;