[CDBI] Class::DBI vs DBIx::Class

Dmitri Bichko dbichko at aveopharma.com
Wed Jan 18 18:20:53 GMT 2006

If 24/7 uptime is necessary and a few failed queries are not acceptable,
I believe the Right Thing to do is run the database as a cluster: bring
up the new schema as a new node, transfer users to it and then change
the existing installation.  Admittedly, I don't have much experience
with this sort of thing.

Generally, I don't know how well any database can be expected to deal
with schema changes during the lifetime of a transaction.  What if a
query is actually scanning that index as you are dropping it?

On the other hand, I've had a lot of problems with postgres prepared
statements and how the planner handles them.  For me at least, the
possibility that the planner will do better on complicated queries
knowing the actual bind values (rare big wins) outweighed the time spent
reparsing the queries on every execute (frequent small losses), so I
just turn them off.  YMMV of course.


> -----Original Message-----
> From: classdbi-bounces at lists.digitalcraftsmen.net 
> [mailto:classdbi-bounces at lists.digitalcraftsmen.net] On 
> Behalf Of John Siracusa
> Sent: Wednesday, January 18, 2006 1:07 PM
> To: Class::DBI
> Subject: Re: [CDBI] Class::DBI vs DBIx::Class
> On 1/18/06, Dmitri Bichko <dbichko at aveopharma.com> wrote:
> >> Maybe...I'll try it.  But it won't help in a web server 
> environment 
> >> because of the obvious race.
> > 
> > How often do you have schema changes in a running 
> application, anyway? 
> > Seems a little sketchy to begin with.
> In a 24/7 webapp, you either never change the schema or you 
> do it while it's running.  Both are preferable to any 
> downtime.  Also, a "schema change" can be as simple as adding 
> or dropping an index.  "Sketchy" or not, sometimes things 
> like this are necessary.
> -John
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