Re: function side effects

Tatsuo Ishii wrote:
> Hi,
>
> I'm wondering if we could detect a funcion has a side effect,
> i.e. does a write to database. This is neccessary for pgpool to decide
> if a qeury should to be sent to all of databases or not. If a query
> includes functions which do writes to database, it should send the
> query to all of databases, otherwise the contents of databases go into
> inconsistent state.

I was talking about this to someone in Cuba and one conclusion we
reached was that this was a fairly difficult task -- consider that
someone may choose to define an innocent-looking operator using a
volatile function. If you only examine things that look like functions
in the query you will miss those. The only way to figure out whether a
query has a write effect is to ask the server about the whole query.

--
Alvaro Herrera http://www.CommandPrompt.com/
The PostgreSQL Company - Command Prompt, Inc.