Re: PostgreSQL questions

On 2010-03-12, Carel Combrink <s25291930(at)tuks(dot)co(dot)za> wrote:
> Dear PostgreSQL novice list,
>
> I am starting development on an application that requires the use of a
> Database. I am considering MySQL vs PostgreSQL and have done extensive
> (perhaps incomplete) research on both of these.
>
> I have 2 questions about PostgreSQL:
> 1.) Is there a difference in running PostgreSQL on Windows vs Linux. I
> am a Windows user but have a Linux box. For the application I am
> leaning more to Linux. Is there advantages or factors I should
> consider when choosing the OS?

It works better on linux, not that it's flaky on windows,
it's designed from a posix standpoint, and just fits better with the
OS on linux.

> 2.) This question is related to triggers. Can I use a trigger to
> notify my external application about a change in the database.

Use notify for this.

Notify is a (postgres specific) SQL command that can be executed as a
query or by a trigger. it will send an alert to any process that is
listening for that notify.

> I am
> looking at using QT for development because of its platform
> independence. Thus the complete question is: Can I notify the QT
> application that data was added to the database (using a trigger)
> without having to query the database the whole time?

notify can be listened for using [p]select() in combination with some
libpq calls, you can do that in a thread or poll periodically from
the application's idle loop.

> The specifications for the application are real-time to semi-real-time
> thus I need an OS with semi-real-time characteristics (Windows is not
> as far as I know, that is why Linux is a good option). And I want to
> notifying the application of changes in the database as soon as they
> happen, this will help with the real-time aspect.
>
> Hope I can get this sorted soon as development should start asap.