Hi Florian,
can you explain why do you state that "default isolation level is assumed to
be
serializable, of course", when you explicitly specify isolation level for
every session - why should he default matter at all?
When I am trying to reproduce the scenario which you have posted, I am
observing different results. Here is my full scenario:
Session 1. Setting up:
CREATE TABLE cars( license_plate VARCHAR NOT NULL, reserved_by VARCHAR NULL
);
INSERT INTO cars(license_plate)
VALUES ('SUPRUSR'),('MIDLYPH');
Session 2: W1
BEGIN ISOLATION LEVEL SERIALIZABLE;
UPDATE cars SET reserved_by = 'Julia' WHERE license_plate = 'SUPRUSR' AND reserved_by IS NULL;
SELECT * FROM Cars
WHERE license_plate IN('SUPRUSR','MIDLYPH');
Session 3: W2
BEGIN ISOLATION LEVEL SERIALIZABLE;
UPDATE cars SET reserved_by = 'Ryan' WHERE license_plate = 'MIDLYPH' AND reserved_by IS NULL;
COMMIT;
Session 4: R
BEGIN ISOLATION LEVEL SERIALIZABLE READ ONLY;
SELECT * FROM Cars
WHERE license_plate IN('SUPRUSR','MIDLYPH');
Session 2: W1
COMMIT;
ERROR: could not serialize access due to read/write dependencies among
transactions
What am I doing wrong?
Thank you for your help!
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