Re: Phantom Read

From: Robert Klemme <bob.news_at_gmx.net>
Date: Wed, 8 Jun 2005 13:35:27 +0200
Message-ID: <3go3h7Fcg8juU1@individual.net>

dd wrote:
> I am a bit confused by exactly what constitute a Phantom Read. Does
> it include ONLY the case where ADDITIONAL rows have been added during
> 2 queries. Then what about rows DELETED between 2 queries? I have
> this concern because many textbooks do define Phantom read as
> addition of rows but never mention anything about removed rows.

AFAIK "Phantom reads" just refer to rows added after an earlier read. If you have deleted rows it's a nonrepeatable read. See chapter "Data Concurrency and Consistency" of the Concepts document.

> If Oracle or any database says its Serializable isolation level does
> prevent Phantom Read, can I assume that it means no rows inserted nor
> DELETED between 2 queries?

Yes, because Serializable prevents phantom reads *and* nonrepeatable reads.

Kind regards

robert Received on Wed Jun 08 2005 - 06:35:27 CDT