Decrease minimum deletes percentage in TMP #14893
Open
+13
−3
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
github-project-automation
bot
moved this to Open
in OpenSearch Lucene & Core Performance Tracking
msokolov
reviewed
Jul 3, 2025
| @@ -139,9 +139,9 @@ public double getMaxMergedSegmentMB() { | |||
| * amplification factor will lead to higher CPU and I/O activity as indicated above. | |||
| */ | |||
| public TieredMergePolicy setDeletesPctAllowed(double v) { | |||
| if (v < 5 || v > 50) { | |||
| if (v <= 0 || v > 50) { | |||
There was a problem hiding this comment.
I like that we still enforce > 0. It makes it more apparent that you are approaching a singular pathological case as you go to 0.001 or whatever
mikemccand
reviewed
Jul 5, 2025
| @@ -130,7 +130,7 @@ public double getMaxMergedSegmentMB() { | |||
| /** | |||
| * Sets the maximum percentage of doc id space taken by deleted docs. The denominator includes | |||
| * both active and deleted documents. Lower values make the index more space efficient at the | |||
| * expense of increased CPU and I/O activity. Values must be between 5 and 50. Default value is | |||
| * expense of increased CPU and I/O activity. Values must be between 0 and 50. Default value is | |||
There was a problem hiding this comment.
Can we enhance this javadoc to note the dangers of very low (< 5%) target deletions? Something like:
Values below 5% can lead to exceptionally high merge cost where indexing will continuously
merge nearly all segments, and select newly merged segments immediately for merging again,
often forcing degenerate merge selection like singleton merges. If you venture into this dark
forest, consider limiting the maximum number of concurrent merges and threads (link to
ConcurrentMergeScheduler's setMaxMergesAndThreads) as a coarse attempt to bound the
otherwise pathological indexing behavior.
There was a problem hiding this comment.
Thank you for the suggestion @mikemccand! I added the paragraph almost exactly as you wrote it.
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
Description
This will allow users to set lower deletes percentages on their merge policies, which can be used to create indexes that are more efficient to search.
Previous discussion: #11761