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_r298304091
##########
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:
Something else to consider: let's say that we generate multiple locations
for each split now, we will run through the determineLocation multiple times
(vs. once) to generate locations that most likely are not used later down the
code path. This means that we spend more cycles on TezAM, potentially
increasing the query execution time there always where the benefits are only
seen in rejection cases....
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