Am 14.04.2010 15:22, schrieb Ted Zlatanov:
On Wed, 14 Apr 2010 15:02:29 +0200 "Jean-Pierre Bergamin"<ja...@ractive.ch>
wrote:
JB> The metrics are stored together with a timestamp. The queries we want to
JB> perform are:
JB> * The last value of a specific metric of a device
JB> * The values of a specific metric of a device between two timestamps t1
and
JB> t2
Make your key "devicename-metricname-YYYYMMDD-HHMM" (with whatever time
sharding makes sense to you; I use UTC by-hours and by-day in my
environment). Then your supercolumn is the collection time as a
LongType and your columns inside the supercolumn can express the metric
in detail (collector agent, detailed breakdown, etc.).
Just for my understanding. What is "time sharding"? I couldn't find an
explanation somewhere. Do you mean that the time-series data is rolled
up in 5 minues, 1 hour, 1 day etc. slices?
So this would be defined as:
<ColumnFamily Name="measurements" ColumnType="Super"
CompareWith="UTF8Type" CompareSubcolumnsWith="LongType" />
So when i want to read all values of one metric between two timestamps
t0 and t1, I'd have to read the supercolumns that match a key range
(device1:metric1:t0 - device1:metric1:t1) and then all the supercolumns
for this key?
Regards
James
