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improve javadocs/comments 

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1559086 13f79535-47bb-0310-9956-ffa450edef68
This commit is contained in:
Michael McCandless 2014-01-17 12:06:08 +00:00
parent 021b937b27
commit f33eb408b9
1 changed files with 17 additions and 7 deletions
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24
lucene/core/src/java/org/apache/lucene/index/TieredMergePolicy.java
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@ -154,9 +154,12 @@ public class TieredMergePolicy extends MergePolicy {
}
/** Controls how aggressively merges that reclaim more
* deletions are favored. Higher values favor selecting
* merges that reclaim deletions. A value of 0.0 means
* deletions don't impact merge selection. */
* deletions are favored. Higher values will more
* aggressively target merges that reclaim deletions, but
* be careful not to go so high that way too much merging
* takes place; a value of 3.0 is probably nearly too
* high. A value of 0.0 means deletions don't impact
* merge selection. */
public TieredMergePolicy setReclaimDeletesWeight(double v) {
if (v < 0.0) {
throw new IllegalArgumentException("reclaimDeletesWeight must be >= 0.0 (got " + v + ")");
@ -255,12 +258,16 @@ public class TieredMergePolicy extends MergePolicy {
* merge. */
protected static abstract class MergeScore {
/** Sole constructor. (For invocation by subclass
* constructors, typically implicit.) */
* constructors, typically implicit.) */
protected MergeScore() {
}
/** Returns the score for this merge candidate; lower
* scores are better. */
abstract double getScore();
/** Human readable explanation of how the merge got this
* score. */
abstract String getExplanation();
}
@ -437,9 +444,12 @@ public class TieredMergePolicy extends MergePolicy {
totBeforeMergeBytes += info.sizeInBytes();
}
// Measure "skew" of the merge, which can range
// from 1.0/numSegsBeingMerged (good) to 1.0
// (poor):
// Roughly measure "skew" of the merge, i.e. how
// "balanced" the merge is (whether the segments are
// about the same size), which can range from
// 1.0/numSegsBeingMerged (good) to 1.0 (poor). Heavily
// lopsided merges (skew near 1.0) is no good; it means
// O(N^2) merge cost over time:
final double skew;
if (hitTooLarge) {
// Pretend the merge has perfect skew; skew doesn't