Robin Infant A created HBASE-28692:
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Summary: 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
Attachments: DataFlow.png, HbaseGet.java, 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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