Re: Common Table Expressions applied; some issues remain

Greg Stark wrote:
> On Wed, May 27, 2009 at 12:47 AM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> I'm not too thrilled about that solution because it still eliminates
>> predictability of execution of volatile functions.
> 
> How so? It means the volatile function might only be executed for the
> matching rows but the rows will still have the same value for the same
> rows for all references to the CTE which seems like the key property
> to me.

A volatile function could have side-effects, ie. insert rows to another 
table. I would not recommend a design that relies on such behavior, but 
it should be predictable how often the volatile function is run if you 
do that.

--   Heikki Linnakangas  EnterpriseDB   http://www.enterprisedb.com