odraese commented on a change in pull request #690: HIVE-21910: Multiple target
location generation in HostAffinitySplitLocationProvider
URL: https://github.com/apache/hive/pull/690#discussion_r298302912
##########
File path:
ql/src/java/org/apache/hadoop/hive/ql/exec/tez/HostAffinitySplitLocationProvider.java
##########
@@ -72,11 +78,17 @@ public HostAffinitySplitLocationProvider(List<String>
knownLocations) {
FileSplit fsplit = (FileSplit) split;
String splitDesc = "Split at " + fsplit.getPath() + " with offset= " +
fsplit.getStart()
+ ", length=" + fsplit.getLength();
- List<String> preferredLocations = preferLocations(fsplit);
- String location =
- preferredLocations.get(determineLocation(preferredLocations,
fsplit.getPath().toString(),
- fsplit.getStart(), splitDesc));
- return (location != null) ? new String[] { location } : null;
+ List<String> preferredLocations = new ArrayList<>(preferLocations(fsplit));
+ List<String> finalLocations = new ArrayList<>(numberOfLocations);
+ // Generate new preferred locations until we need more, or we do not have
any preferred
+ // location left
+ while (finalLocations.size() < numberOfLocations &&
preferredLocations.size() > 0) {
+ String nextLocation =
preferredLocations.get(determineLocation(preferredLocations,
+ fsplit.getPath().toString(), fsplit.getStart(), splitDesc));
+ finalLocations.add(nextLocation);
+ preferredLocations.remove(nextLocation);
Review comment:
Instead of having an own array list, from which we remove 1 for each split
(which is quite often), we could simply pass down numberOfLocations (and
decrement it) to determineLocation and change
`int index = Hashing.consistentHash(hash1, locations.size());`
to
`int index = Hashing.consistentHash(hash1, numLocations);`
in determineLocations. Seems to be more efficient.
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