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Re: incoherent view of serializable transactions

From: Stephan Szabo <sszabo(at)megazone(dot)bigpanda(dot)com>
To: Kevin Grittner <Kevin(dot)Grittner(at)wicourts(dot)gov>
Cc: Gregory Stark <stark(at)enterprisedb(dot)com>,Emmanuel Cecchet <manu(at)frogthinker(dot)org>,pgsql-hackers(at)postgresql(dot)org, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Subject: Re: incoherent view of serializable transactions
Date: 2008-12-23 17:15:38
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-hackers
On Tue, 23 Dec 2008, Kevin Grittner wrote:

> The page locking provides this because every index page or data page
> the serializable transaction looks at is locked against updates until
> the end of the transaction.  If it can see all the COLUMN=0 rows
> through an index, the index locks protect the transaction.  If a table
> scan is required, the entire table is locked against all
> modifications.  (That's right, it is not unusual to have entire tables
> locked against any modification until the end of a database
> transaction.)

Well, predicate locking for serializable also should only lock the
appropriate conditions. Getting a deadlock between two serializable
transactions for conditions that can be serialized would seemingly also be
disallowed by the definition of serializable since there would exist no
serial ordering of the transactions that has that effect.

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