Path: csiph.com!v102.xanadu-bbs.net!xanadu-bbs.net!news.glorb.com!news-out.readnews.com!news-xxxfer.readnews.com!postnews.google.com!glegroupsg2000goo.googlegroups.com!not-for-mail From: Lew Newsgroups: comp.lang.java.programmer Subject: Re: JDBC transaction isolation Date: Thu, 3 May 2012 18:32:31 -0700 (PDT) Organization: http://groups.google.com Lines: 89 Message-ID: <15050921.112.1336095151817.JavaMail.geo-discussion-forums@pbnh4> References: <4fa2aa0c$0$294$14726298@news.sunsite.dk> <4fa2d5c7$0$288$14726298@news.sunsite.dk> <24360777.22.1336090546668.JavaMail.geo-discussion-forums@pbfk7> <4fa32f5d$0$285$14726298@news.sunsite.dk> NNTP-Posting-Host: 69.28.149.29 Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable X-Trace: posting.google.com 1336095152 25682 127.0.0.1 (4 May 2012 01:32:32 GMT) X-Complaints-To: groups-abuse@google.com NNTP-Posting-Date: Fri, 4 May 2012 01:32:32 +0000 (UTC) In-Reply-To: <4fa32f5d$0$285$14726298@news.sunsite.dk> Complaints-To: groups-abuse@google.com Injection-Info: glegroupsg2000goo.googlegroups.com; posting-host=69.28.149.29; posting-account=CP-lKQoAAAAGtB5diOuGlDQk0jIwmH0T User-Agent: G2/1.0 Xref: csiph.com comp.lang.java.programmer:14241 Arne Vajh=F8j wrote: > Lew wrote: >> Richard Maher wrote: >>> Arne Vajh=F8j wrote ... >>>> Almost all database have it at the SQL level: >>>> >>>> http://dev.mysql.com/doc/refman/5.5/en/set-transaction.html >>>> http://www.postgresql.org/docs/9.1/static/sql-set-transaction.html and >>>> http://www.postgresql.org/docs/9.1/static/transaction-iso.html >>>> http://msdn.microsoft.com/en-us/library/ms173763.aspx >>>> http://docs.oracle.com/cd/B10500_01/server.920/a96524/c21cnsis.htm >>> >>> Is anyone else of the opinion that Oracle really does not support the >>> serializable isolation level? (At least not in the way that SQL Server,= Rdb, >> >> Are you referring to their database product or some other product, such = as Java? >> >>> and I'm sure others do) That is, it doesn't prevent inserts to the othe= r >>> txn's result-set,touched-rows by locking but rather fudges some sort of >>> snapshot/consistent-view of old data. (And even then with restrictions) >>> Eg: - select count(*) from employees where dept_code=3D1; >> >> They do support SERIALIZABLE isolation, and properly by all evidence: >> >> >> "ISOLATION LEVEL Clause >> >> "Use the ISOLATION LEVEL clause to specify how transactions containing d= atabase >> modifications are handled. >> >> "The SERIALIZABLE setting specifies serializable transaction isolation m= ode as defined in the >> SQL standard. If a serializable transaction contains data manipulation l= anguage (DML) that >> attempts to update any resource that may have been updated in a transact= ion uncommitted at >> the start of the serializable transaction, then the DML statement fails.= " >> >> See also >> >> >> There's nothing in the definition of SERIALIZABLE transactions that requ= ires locking. >> >> >> So whatever anyone else's opinion, or yours, the facts seem to be that O= racle Database=20 >> properly supports SERIALIZABLE transaction isolation. Why do you ask for= opinion when=20 >> facts are in evidence? >=20 > They meet the definition for transaction isolation level serializable. Q.E.D. > It is more questionable whether MVCC (and Oracle is actually not the > only database vendor using MVCC !=3D meet what most people associate > with serializable. What does that matter? The term "serializable transaction isolation" is a t= erm of art, with a=20 specific definition. Whatever "most people" associate with it notwithstandi= ng. It's an objective=20 term with testable criteria for compliance. Oracle meets the test. People are not entitled to wrong opinions on the definitions of terms of ar= t, or any opinions, as to their definition. > Well - I think should use the database definition and not the > English definition when it actually is a database. +1 > But I will not be surprised when somebody ask questions about it. Surprise at the question is one thing. A correct answer is another. I'm not evincing surprise at the question, only pointing out that the answe= r is not a matter of opinion. --=20 Lew