Re: incoherent view of serializable transactions - Mailing list pgsql-hackers

From Peter Eisentraut
Subject Re: incoherent view of serializable transactions
Date
Msg-id 4959E24B.9040900@gmx.net
Whole thread Raw
In response to Re: incoherent view of serializable transactions  (Greg Stark <greg.stark@enterprisedb.com>)
Responses Re: incoherent view of serializable transactions  ("Kevin Grittner" <Kevin.Grittner@wicourts.gov>)
List pgsql-hackers
Greg Stark wrote:
> And I don't see why you discard "visibility" as unimportant. All the 
> transaction isolations are defined in terms of the results if the 
> transactions. Those results include both the database state and the data 
> returned by the queries. Otherwise "phantom read" is a meaningless concept.

Basically, if he wants to make a rigid argument that some scenario 
violates the serializability promise, then it is necessary to prove:

(1) There is no serial schedule for the set of transactions that 
achieves the same outcome.  (This proof is probably hard to work out, as 
many "there is no" proofs are.)

- or -

(2) A phantom read situation occurs.

His original argument uses terms like "window" where something is 
"visible" (to whom?), which can probably be transformed into a proof for 
(2), but is not convincing (to me) by itself.



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