On 5/01/2010 3:30 PM, Yan Cheng Cheok wrote:
>>> What is the actual problem you are trying to solve?
>
> I am currently developing a database system for a high speed measurement machine.
>
> The time taken to perform measurement per unit is in term of ~30 milliseconds. We need to record down the measurement
resultfor every single unit. Hence, the time taken by record down the measurement result shall be far more less than
milliseconds,so that it will have nearly 0 impact on the machine speed (If not, machine need to wait for database to
finishwriting, before performing measurement on next unit)
The commit_delay and synchronous_commit pararmeters may help you if you
want to do each insert as a separate transaction. Note that with these
parameters there's some risk of very recently committed data being lost
if the server OS crashes or the server hardware is powered
off/power-cycled unexpectedly. PostgreSQL its self crashing shouldn't
cause loss of the committed data, though.
Alternately, you can accumulate small batches of measurements in your
app and do multi-valued INSERTs once you have a few (say 10) collected
up. You'd have to be prepared to lose those if the app crashed though.
Another option is to continue using your flat file, and have a "reader"
process tailing the flat file and inserting new records into the
database as they become available in the flat file. The reader could
batch inserts intelligently, keep a record on disk of its progress,
rotate the flat file periodically, etc.
--
Craig Ringer