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https://issues.apache.org/jira/browse/HBASE-13374?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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stack updated HBASE-13374:
--------------------------
Priority: Blocker (was: Major)
> Small scanners (with particular configurations) do not return all rows
> ----------------------------------------------------------------------
>
> Key: HBASE-13374
> URL: https://issues.apache.org/jira/browse/HBASE-13374
> Project: HBase
> Issue Type: Bug
> Affects Versions: 1.0.0, 2.0.0, 1.1.0, 0.98.13
> Reporter: Jonathan Lawlor
> Priority: Blocker
> Attachments: small-scanner-data-loss-tests-0.98.patch,
> small-scanner-data-loss-tests-branch-1.0+.patch
>
>
> I recently ran into a couple data loss issues with small scans. Similar to
> HBASE-13262, these issues only appear when scans are configured in such a way
> that the max result size limit is reached before the caching limit is
> reached. As far as I can tell, this issue affects branches 0.98+
> I should note that after investigation it looks like the root cause of these
> issues is not the same as HBASE-13262. Rather, these issue are caused by
> errors in the small scanner logic (I will explain in more depth below).
> Furthermore, I do know that the solution from HBASE-13262 has not made its
> way into small scanners (it is being addressed in HBASE-13335). As a result I
> made sure to test these issues with the patch from HBASE-13335 applied and I
> saw that they were still present.
> The following two issues have been observed (both lead to data loss):
> 1. When a small scan is configured with a caching value of Integer.MAX_VALUE,
> and a maxResultSize limit that is reached before the region is exhausted,
> integer overflow will occur. This eventually leads to a preemptive skip of
> the regions.
> 2. When a small scan is configured with a maxResultSize that is smaller than
> the size of a single row, the small scanner will jump between regions
> preemptively. This issue seems to be because small scanners assume that,
> unless a region is exhausted, at least 2 rows will be returned from the
> server. This assumption isn't clearly state in the small scanners but is
> implied through the use of {{skipRowOfFirstResult}}.
> Again, I would like to stress that the root cause of these issues is *NOT*
> related to the cause of HBASE-13262. These issues occur because of
> inappropriate assumption made in the small scanner logic. The inappropriate
> assumptions are:
> 1. Integer overflow will not occur when incrementing caching
> 2. At least 2 rows will be returned from the server unless the region has
> been exhausted
> I am attaching a patch that contains tests to display these issues. If these
> issues should be split into separate JIRAs please let me know.
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