Not sure I understand what you mean. Are you using the flow file to
trigger ExecuteStreamCommand to schedule a cron job? Or do you mean
scheduling a processor to run in NiFi? Or something else?
On Mon, Oct 29, 2018 at 3:58 PM l vic <[email protected]> wrote:
>
> QDT works, eg it can detect change in MaximumValue column but how can I use
> it to schedule cron job? I know it's possible to schedule cron from UI but
> how can i do it based on the value of attribute?
> Thank you again,
> V.
>
> On Mon, Oct 29, 2018 at 12:39 PM Matt Burgess <[email protected]> wrote:
>>
>> Victor,
>>
>> Yes, both QDT and GTF would generate something like "SELECT * from
>> myTable where event_time > X", and QDT will execute it and update X.
>> So if event_time is always increasing, it will continue to pick up the
>> same row(s).
>>
>> That's a curious use case, maybe NiFi could handle other parts of it
>> so you wouldn't need to update a single row in an external database
>> table?
>>
>> Regards,
>> Matt
>>
>> On Mon, Oct 29, 2018 at 12:36 PM l vic <[email protected]> wrote:
>> >
>> > What if have only one row and update the values in it? Will QDT fetch
>> > updates?
>> > Thank you,
>> > Victor
>> >
>> >
>> > On Mon, Oct 29, 2018 at 11:54 AM Matt Burgess <[email protected]> wrote:
>> >>
>> >> You can use QueryDatabaseTable (QDT) for this, you'd set your
>> >> "event_time" column as the "Maximum Value Column(s)" property in the
>> >> processor. The first time QDT executes, it will fetch all the rows
>> >> (since it has not seen event_time before), then it will keep track of
>> >> the largest value of event_time. As new rows are added (with larger
>> >> event_time values), QDT will only fetch the rows whose event_time is
>> >> greater than the largest one it's seen. Then it updates its "largest
>> >> seen value" and so on.
>> >>
>> >> GenerateTableFetch (GTF) is another option, it works in a similar
>> >> fashion, except that it does not fetch the rows itself, instead it
>> >> generates flow files containing SQL statements that you can send
>> >> downstream to perhaps ExecuteSQL in order to actually fetch the rows.
>> >> GTF is often used in place of QDT if you'll be fetching a large number
>> >> of rows in each statement, as you can distribute the SQL flow files
>> >> among the nodes in a cluster, to do the fetch in parallel.
>> >>
>> >> Regards,
>> >> Matt
>> >>
>> >> On Mon, Oct 29, 2018 at 11:13 AM l vic <[email protected]> wrote:
>> >> >
>> >> > Hi,
>> >> > i have "event_time" field in SQLite database that means epoch time for
>> >> > triggering of external event. What processor(s) can i use to implement
>> >> > schedule monitoring/ execution based on change in "event_time" value?
>> >> > Thanks,
