Re: Independent comparison of PostgreSQL and MySQL

Where is the claim about transactions being visible before crash-safety in
his thesis? I didn't find it via a quick search of the pdf.

On Wed, Oct 8, 2014 at 2:22 PM, Kevin Grittner <kgrittn(at)ymail(dot)com> wrote:

> Thomas Kellerer <spam_eater(at)gmx(dot)net> wrote:
>
> > There are several quirks in MySQL which might make real life
> > harder than a plain feature comparison might express.
> >
> > One of the really annoying things is that it actually lies about
> > what it is doing.
>
> Along those lines, I remember when that in a 2009 paper on
> concurrency techniques[1] Michael J. Cahill noted that the work of
> a transaction in MySQL is made visible to other transactions, and
> the COMMIT request (or stand-alone statement) returns to the
> caller, before the work of the transaction is guaranteed to appear
> if there is a crash and subsequent recovery. Essentially, the only
> mode available in MySQL was what you get with PostgreSQL if you
> request synchronous_commit = off. PostgreSQL defaults to waiting
> to make the transaction visible and returning to the caller until
> after it is guarateed to persist; although it gives you the option,
> on a transaction-by-transaction basis, to take the faster route of
> skipping that guarantee.
>
> (Apologies if that was covered in one of the referenced links -- I
> skimmed them and didn't spot this issue, but it might be there
> somewhere....)
>
> --
> Kevin Grittner
> EDB: http://www.enterprisedb.com
> The Enterprise PostgreSQL Company
>
> [1] Michael James Cahill. 2009.
> Serializable Isolation for Snapshot Databases.
> Sydney Digital Theses.
> University of Sydney, School of Information Technologies.
> http://hdl.handle.net/2123/5353
>
>
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--
Mark Callaghan
mdcallag(at)gmail(dot)com