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https://issues.apache.org/jira/browse/OMID-102?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16570300#comment-16570300
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ASF GitHub Bot commented on OMID-102:
-------------------------------------
Github user JamesRTaylor commented on a diff in the pull request:
https://github.com/apache/incubator-omid/pull/41#discussion_r207919955
--- Diff:
hbase-coprocessor/src/test/java/org/apache/omid/transaction/TestSnapshotFilter.java
---
@@ -226,8 +222,115 @@ public void testGetFirstResult() throws Throwable {
}
@Test(timeOut = 60_000)
- public void testGetSecondResult() throws Throwable {
--- End diff --
Is there a test which would have failed without this patch (i.e. one that
demonstrates the need for having the visibility filtering done as a pure HBase
filter)?
> Implement visibility filter as pure HBase Filter
> ------------------------------------------------
>
> Key: OMID-102
> URL: https://issues.apache.org/jira/browse/OMID-102
> Project: Apache Omid
> Issue Type: Sub-task
> Reporter: James Taylor
> Assignee: Yonatan Gottesman
> Priority: Major
>
> The way Omid currently filters through it's own RegionScanner won't work the
> way it's implemented (i.e. the way the filtering is done *after* the next
> call). The reason is that the state of HBase filters get messed up since
> these filters will start to see cells that it shouldn't (i.e. cells that
> would be filtered based on snapshot isolation). It cannot be worked around by
> manually running filters afterwards because filters may issue seek calls
> which are handled during the running of scans by HBase.
>
> Instead, the filtering needs to be implemented as a pure HBase filter and
> that filter needs to delegate to the other, delegate filter once it's
> determined that the cell is visible. See Tephra's TransactionVisibilityFilter
> and they way it calls the delegate filter (cellFilters) only after it's
> determined that the cell is visible. You may run into TEPHRA-169 without
> including the CellSkipFilter too.
> Because it'll be easier if you see shadow cells *before* their corresponding
> real cells you can prefix instead of suffix the column qualifiers to
> guarantee that you'd see the shadow cells prior to the actual cells. Or you
> could buffer cells in your filter prior to omitting them. Another issue would
> be if the shadow cells aren't found and you need to consult the commit table
> - I suppose if the shadow cells are first, this logic would be easier to know
> when it needs to be called.
>
> To reproduce, see the Phoenix unit tests
> FlappingTransactionIT.testInflightUpdateNotSeen() and
> testInflightDeleteNotSeen().
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