Re: How to reproduce serialization failure for a read only transaction.

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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