Re: wide row insert via Postgres jdbc driver

On Tue, 23 Sep 2014 14:12:22 +0200
Thomas Kellerer <spam_eater(at)gmx(dot)net> wrote:

> Sameer Kumar schrieb am 23.09.2014 um 07:24:
> > I am working with a vendor and planning to deploy their application
> > on PostgreSQL as backend. They have cautioned the customer that
> > PostgreSQL's jdbc driver v9.1 (build 900) has issues which causes
> > deadlocks while "wide record inserts".
>
> Can you be a bit more explicit?
> I have never heard the term "wide record inserts" before

I've heard these terms before. "Wide" generally means at least one of the
following:

* A large number of columns
* At least 1 column with a lot of data

Of course, both of those criteria are incredibly subjective. How many columns
is a "large" number? How much data is a "lot"?

It generally boils down to he fact that pushing a lot of data (whether many
columns or a single column with a lot of data) takes longer than pushing small
amounts of data (big surprise) and as a result, the statistical chance that
the operatin will collide with a conflicting operation (causing, in this case,
a deadlock) is increased.

As you mention, it's usually something that people with poorly written
applications complain about. I.e. "our application works just fine in our test
environment, so your server must be too slow ... get a faster server"

Of course, the real problem is that the application was written with a large
number of braindead assumptions (things will always be fast; our tests never
encounter deadlocks, so they can't happen, etc) I've dealt directly with this
back in my consulting days: clients who insisted that the correct way to fix
their crashes was to buy faster hardware. The annoying thing is that such an
approach _appears_ to fix the problem, because the faster hardware causes the
chance of the problem occuring to be less, and in the mind of people who don't
understand concurrent programming, that's "fixed".

The amount of really badly written software out there is a very large number.

--
Bill Moran
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http://gamesbybill.com