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https://issues.apache.org/jira/browse/HBASE-28692?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17863700#comment-17863700
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Istvan Toth edited comment on HBASE-28692 at 7/8/24 7:54 AM:
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I am not familiar with that part of the code, [~zhangduo].
was (Author: stoty):
I am no familiar with that part of the code, [~zhangduo].
> The GET call for column keys becomes significantly slower when it follows
> lexicographically prior deleted cells. [PERFORMANCE BLOAT]
> ------------------------------------------------------------------------------------------------------------------------------------
>
> Key: HBASE-28692
> URL: https://issues.apache.org/jira/browse/HBASE-28692
> Project: HBase
> Issue Type: Bug
> Components: regionserver
> Affects Versions: 2.5.5
> Environment: Ubuntu 22.04.4 LTS - 64 Bit
> Reporter: Robin Infant A
> Priority: Critical
> Attachments: DataFlow.png, HbaseGet.java,
> RegionServerDummyKeyAdded.png, RegionServerFlame.png
>
>
> *Steps to Reproduce :*
> 1. Ensure the column family of the table is configured with MIN_VERSION = 1
> and KEEP_DELETED_CELLS = true to ensure that deleted cells remain even after
> deletion (this is to ensure that flush/compaction doesn't remove deleted
> cells).
> 2. Add multiple column keys against a single row key. In this case, use a
> timestamp (SET1).
> 3. Use a GET call (GET1) with an iterator-based design to get all the keys.
> Use the ColumnPaginationFilter and RangeKeyFilter to achieve this (refer to
> the attached HbaseGet.java file for implementation details).
> 4. Note the time taken for GET1 (e.g., ~1 second for 100,000 entries).
> 5. Delete all the added column keys (SET1).
> 6. Add another set of 100,000 entries (SET2).
> 7. Use the GET call again (GET2) to retrieve the data and note the time taken.
> *Expected Behavior:*
> The time taken for GET2 should be similar to GET1, approximately ~1 second.
> *Actual Behavior:*
> The time taken for GET2 increases significantly, approximately 60 seconds,
> which is ~50 times longer than GET1.
> *Additional Information:*
> i) If, after the first delete (SET1), data with lexicographically prior
> characters (e.g., "0") are added before the deleted cells (timestamp), the
> GET call time remains consistent with GET1, approximately 1200 ms.
> ii) If all 200,000 entries are retrieved without deleting the first set
> (SET1), the total time is around 2 to 3 seconds. However, deleting SET1
> causes GET2 to take 50 times longer than GET1.
> *Suggested Fix:*
> Temporarily, to fix this issue, add a dummy column key with a
> lexicographically prior character (e.g., "0") to ensure consistent GET call
> times.
> *Note:*
> Please refer to the attached [^HbaseGet.java], RegionserverFlameGraph and
> dataFlow for detailed steps to reproduce the issue.
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