Github user JamesRTaylor commented on a diff in the pull request:
https://github.com/apache/phoenix/pull/8#discussion_r16699150
--- Diff:
phoenix-core/src/main/java/org/apache/phoenix/iterate/DefaultParallelIteratorRegionSplitter.java
---
@@ -138,14 +146,10 @@ public boolean apply(HRegionLocation location) {
// split each region in s splits such that:
// s = max(x) where s * x < t
//
- // The idea is to align splits with region boundaries. If rows are
not evenly
- // distributed across regions, using this scheme compensates for
regions that
- // have more rows than others, by applying tighter splits and
therefore spawning
- // off more scans over the overloaded regions.
- int splitsPerRegion = getSplitsPerRegion(regions.size());
// Create a multi-map of ServerName to List<KeyRange> which we'll
use to round robin from to ensure
// that we keep each region server busy for each query.
- ListMultimap<HRegionLocation,KeyRange> keyRangesPerRegion =
ArrayListMultimap.create(regions.size(),regions.size() * splitsPerRegion);;
+ int splitsPerRegion = getSplitsPerRegion(regions.size());
+ ListMultimap<HRegionLocation,KeyRange> keyRangesPerRegion =
ArrayListMultimap.create(regions.size(),regions.size() * splitsPerRegion);
--- End diff --
Also, we won't use targetConcurrency and maxConcurrency. Instead we'll add
all guideposts for the regions here (they'll get pruned later when we
apply/intersect them with the scan start/stop row). This will help in a bunch
of ways by dividing the query up into smaller equal sized scans - we won't get
lease expiration exceptions from the server b/c the client will be specifying
smaller chunks. We'll also get better fairness between queries, b/c no one
query will dominate a thread for too long a time. It also simplifies things
quite a bit.
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