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.
Querying an integer field with a fill value will cause a cast error
because the underlying type is a float64 rather than an int64. Add a
function that will coerce the value to the correct type.
It may be more appropriate in the future to have the fill iterator read
the underlying iterator and cast to the appropriate type rather than
coerce the fill value to the correct type, but this solution works for
our current scenario well.
The additional locks shouldn't be necessary due to how the code is used,
but should prevent any potential data races in case we accidentally do
something bad.
The AuxIterator streams points to the underlying iterators. When it
started automatically, race conditions occurred between the stream
closing the iterators and creating iterators from the AuxIterator.
Aux iterators now ask the iterator creator what series will be returned
and determine which aux fields to create based on the results.
The `tsdb.Shards` struct also creates a call iterator around the
iterators returned from each shard.
Fill requires an additional function for IteratorCreator to retrieve the
series that will be returned from the iterator. When fill is required
for an aggregate, the IteratorCreator will be asked what series will be
returned by the created iterator.
When multiple sources are used, emit all points for a certain source
(like cpu) before another source (like mem) regardless of which window
they are in. If the sources are the same, then sort by window.
Continue to ignore tags since we don't need to sort nicely by tags with
a MergeIterator, only SortedMergeIterator.
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.
Out of a list of iterators, an overarching iterator type is chosen and
only iterators of that type are returned for the merge iterator. If a
type can be cast to another type, an extra cast iterator is created to
handle that casting.
The only supported cast is from integers to floats.
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
Jonathan A. Sternberg