Because timestamps at the end instant are not actually part of the interval. This
affected benchmark numbers, since it meant some data points would not be queried
(the interval for the query was based on getDataInterval) and also the
TimestampCheckingOffsets could not use the allWithinThreshold optimization.
This patch introduces a GroupByStrategy concept and two strategies: "v1"
is the current groupBy strategy and "v2" is a new one. It also introduces
a merge buffers concept in DruidProcessingModule, to try to better
manage memory used for merging.
Both of these are described in more detail in #2987.
There are two goals of this patch:
1. Make it possible for historical/realtime nodes to return larger groupBy
result sets, faster, with better memory management.
2. Make it possible for brokers to merge streams when there are no order-by
columns, avoiding materialization.
This patch does not do anything to help with memory management on the broker
when there are order-by columns or when there are nested queries. That could
potentially be done in a future patch.
* new interval based cost function
Addresses issues with balancing of segments in the existing cost function
- `gapPenalty` led to clusters of segments ~30 days apart
- `recencyPenalty` caused imbalance among recent segments
- size-based cost could be skewed by compression
New cost function is purely based on segment intervals:
- assumes each time-slice of a partition is a constant cost
- cost is additive, i.e. cost(A, B union C) = cost(A, B) + cost(A, C)
- cost decays exponentially based on distance between time-slices
* comments and formatting
* add more comments to explain the calculation
BoundFilter:
- For lexicographic bounds, use bitmapIndex.getIndex to find the start and end points,
then union all bitmaps between those points.
- For alphanumeric bounds, iterate through dimValues, and union all bitmaps for values
matching the predicate.
- Change behavior for nulls: it used to be that the BoundFilter would never match nulls,
now it matches nulls if "" is allowed by the lower limit and not excluded by the
upper limit.
Interface changes:
- BitmapIndex: add `int getIndex(value)` to make it possible to get the index for a
value without retrieving the bitmap.
- BitmapIndex: remove `ImmutableBitmap getBitmap(value)`, change callers to `getBitmap(getIndex(value))`.
- BitmapIndexSelector: allow retrieving the underlying BitmapIndex through getBitmapIndex.
- Clarified contract of indexOf in Indexed, GenericIndexed.
Also added tests for SelectorFilter, NotFilter, and BoundFilter.
Gian Merlino
Hyukjin Kwon
Jonathan Wei
Charles Allen
Xavier Léauté
John Wang
jon-wei
Himanshu Gupta
Xavier Léauté
nishant