Jialin Qiao created IOTDB-298:
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Summary: Refactor the "last" and "first" aggregators
Key: IOTDB-298
URL: https://issues.apache.org/jira/browse/IOTDB-298
Project: Apache IoTDB
Issue Type: Improvement
Reporter: Jialin Qiao
We have two aggregators:
last -> return the value of the last data point
max_time -> return the time of the last data point
However, we do not have an aggregator that returns the last time-value pair.
This is very antihuman in a time-series database :(:(:(
I suggest changing the "last" aggregator to return the last time-value pair and
removing the max_time aggregator.
Similar to the "first" aggregator.
One thing we need to pay attention:
for example, select last(s1), last(s2) from root.sg1.d1 . If the two series
have different last time, how we organize the ResultSet? Maybe each line
represents a last point. List this:
time last(s1), last(s2)
1, 1, null
2, null, 1
Or we could forbid using the last aggregator on two series at the same time.
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