Use of the iterator is spread out into both `IteratorCreators` and
inside of the iterators themselves. Part of the interrupt must be
handled inside of the engine so it stops trying to emit points when an
interrupt is found and another part of the interrupt has to happen when
combining the iterators so it doesn't just start reading the next shard.
Previously the call iterator would normalize the time to the interval
for all calls. This meant that when `first()` or `last()` was called
with no group by interval the value would be found for each shard, the
time was normalized, then it tried to find the value between the shards
(but no longer with any time data as that had already been eliminated).
This removes part of the time logic from the call iterators and makes a
new iterator `IntervalIterator` to normalize the times as they come out
of the underlying iterator.
Fixes#5890.
All three of these iterators are supposed to support all four types of
iterators, but the implementation was never done for string or boolean.
Fixes#5886.
A new attribute has been added to points to track how many points were
used to calculate that point. This is particularly useful for finding
the mean as we can then split mean calculation into two phases: one at
the shard level and a second at the shards level.
This optimization is now used so we don't have to hold so many points in
memory while calculating the mean.
Previously reduce iterators just separated points by tags. If you had
identical tags but different names, it would group those together so you
could have these two points:
cpu value=1
mem value=2
When you performed a `mean(value)` call and included both cpu and mem as
sources, it would return one mem series with a value of 1.5 instead of
two serieses.
last() would always return the last output of the iterator (which isn't
necessarily the last time value due to how the merge iterator works) and
first() would always return the first output of the iterator (wrong for
the same reason).
Now the time is kept by the reduce function and the times are wiped as
part of the reduce iterator after the value has been found.
Jonathan A. Sternberg
Ben Johnson