List:General Discussion« Previous MessageNext Message »
From:Madscientist Date:June 13 2003 2:51am
Subject:Re: soft real-time database
View as plain text  
At 05:03 PM 6/12/2003 -0600, Chris Webster wrote:
>Curtis Maurand wrote:
>>I'd write a perl script to pool the device and send the data to the database.
>
>Sorry for not being clearer.  I can get the data into the database 
>fine.  Assuming new values or rows are added once per second, how would a 
>client program go about polling the database to see when a new value was 
>ready?  Check # of rows for a column and when it's incremented grab the 
>latest value?
>
>--Chris

How about this:

Keep a table with a single row as a status indicator. Whenever you add a 
new row of data, update the status record with a new count of samples. 
(samples = samples + 1)... You may even find other interesting things to 
put in this row for diagnostic monitoring.

Your client application can then check the single row to determine if new 
data is available for analysis. It may even be possible to "prescale" some 
of the analysis in the status indicator row... for example summary 
statistics. Using this model you can also move on to a new status record 
when a new time period begins (or with some other criteria) so that you 
have a record of summary trends available.

Updating a single record is not likely to cause significant loading since 
the same record is always in the database cache and in precisely the same 
location. A prepared statement can also help here.

Hope this helps,

_M

Pete McNeil (Madscientist)
President, MicroNeil Research Corporation.

Thread
soft real-time databaseChris Webster12 Jun
  • Re: soft real-time databaseBecoming Digital13 Jun
    • Re: soft real-time databaseCurtis Maurand13 Jun
      • Re: soft real-time databaseChris Webster13 Jun
        • Re: soft real-time databaseMadscientist13 Jun
        • Re: soft real-time databaseCurtis Maurand13 Jun
          • Re: soft real-time databaseChris Webster13 Jun
            • Re: soft real-time databaseCurtis Maurand15 Jun
      • Re: soft real-time databaseBecoming Digital13 Jun
    • Re: soft real-time databaseChris Webster13 Jun