Database datafeed

[DarioCrivelli]

Hi Sinead

Lightstreamer can perform a frequency filter on the updates for each item, but it does not perform any "summing" on field values; it just performs merging of changed and unchanged fields. You can take advantage of Lightstreamer frequency filter in your scenario only if you can feed it with cumulative metric values (to be computed by summing the metrics in the Data Adapter) and subtract the old cumulated values from the new ones on the client side.

If you find this unacceptable, you need to specialize your items.
In fact, as an architectural constraint, the Data Adapter has no knowledge of the details of the client requests, but it only knows the "items", which can be requested by multiple clients with different options.
You can define an item for "Propertya, Metric1 at a frequency of 1 second", one for "Propertya, Metric2 at a frequency of 5 seconds" and so on, choosing suitable names for them. Your Data Adapter should be able to recognize the different items, with their own characteristics, based on their names only, and feed them accordingly.
However, this means that the Data Adapter should provide to Lightstreamer Server two distinct flows of events for the two items. It can perform only one database polling cycle in order to provide both flows, but this mechanism has to be entirely implemented in the Data Adapter code.

Dario

[Sinead]

Thanks for your help Dario. Sinead.