Thread: postgres in realtime mode

hello everybody,
i am using postgres for someime now for storing my maps etc.
Can postgresql can be used in real time domain. I may be using open source rtlinux as rtos.
I mean how i can show it is working as real time os.
Is sth on this issue already available ?

thankyou
quick nitin

2006-06-28 (수), 17:14 +0530, nitin quick 쓰시길:
> hello everybody,
> i am using postgres for someime now for storing my maps etc.
> Can postgresql can be used in real time domain. I may be using open
> source rtlinux as rtos.
> I mean how i can show it is working as real time os.
> Is sth on this issue already available ?
what is real-time as far as a database is concerned?
>
> thankyou
> quick nitin
--
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by realtime i mean predictivity of query response time. I do agree it may vary transacion to transaction but there may be some time factor which i can say i will get response in so many millseconds. This idea of mine is very naive. If i am conceptually wrong please correct me or if you can guide me in this matter i will appreaciate the effort.

regards
quick nitin

quick.nitin@gmail.com ("nitin quick") writes:
> hello everybody,
> i am using postgres for someime now for storing my maps etc.
> Can postgresql can be used in real time domain. I may be using open source rtlinux as rtos.
> I mean how i can show it is working as real time os.
> Is sth on this issue already available ?

Real Time systems generally mandate that tasks are guaranteed to
complete without more than some pre-defined amount of delay.

SQL introduces considerable nondeterminism in that different queries
that look much the same may have dramatically different performance
characteristics.

I don't think you'll be able to guarantee that all queries will
complete in less than some given interval of time.

It's entirely likely that PostgreSQL can run atop some RTOSes; I don't
think it could be safely considered as a candidate component for a
real time system without taking exceeding care to ensure that database
operations were selected carefully.
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Centuries ago, Nostradamus foresaw when quick.nitin@gmail.com ("nitin quick") would write:
> by realtime i mean predictivity of query response time. I do agree
> it may vary transacion to transaction but there may be some time
> factor which i can say i will get response in so many
> millseconds. This idea of mine is very naive. If i am conceptually
> wrong please correct me or if you can guide me in this matter i will
> appreaciate the effort.  regards quick nitin

Conceptually, you're right about what real time means; it's all about
seeking guarantees about worst-time performance that they will not
exceed some pre-defined thresholds.

With a relational database, you're requesting a declarative and
decidedly non-deterministic approach to things, and it doesn't seem
reasonable for that to be compatible with hard RT requirements on
worst-time performance.
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