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https://issues.apache.org/jira/browse/ACCUMULO-2232?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14901918#comment-14901918
]
ASF GitHub Bot commented on ACCUMULO-2232:
------------------------------------------
Github user joshelser commented on a diff in the pull request:
https://github.com/apache/accumulo/pull/47#discussion_r40052512
--- Diff:
core/src/main/java/org/apache/accumulo/core/iterators/Combiner.java ---
@@ -240,15 +299,18 @@ public void init(SortedKeyValueIterator<Key,Value>
source, Map<String,String> op
newInstance.setSource(getSource().deepCopy(env));
newInstance.combiners = combiners;
newInstance.combineAllColumns = combineAllColumns;
+ newInstance.isPartialCompaction = isPartialCompaction;
+ newInstance.deleteHandlingAction = deleteHandlingAction;
return newInstance;
}
@Override
public IteratorOptions describeOptions() {
IteratorOptions io = new IteratorOptions("comb", "Combiners apply
reduce functions to multiple versions of values with otherwise equal keys",
null, null);
- io.addNamedOption(ALL_OPTION, "set to true to apply Combiner to every
column, otherwise leave blank. if true, " + COLUMNS_OPTION
- + " option will be ignored.");
+ io.addNamedOption(ALL_OPTION,
--- End diff --
Nit: unrelated formatting.
> Combiners can cause deleted data to come back
> ---------------------------------------------
>
> Key: ACCUMULO-2232
> URL: https://issues.apache.org/jira/browse/ACCUMULO-2232
> Project: Accumulo
> Issue Type: Bug
> Components: client, tserver
> Reporter: John Vines
>
> The case-
> 3 files with-
> * 1 with a key, k, with timestamp 0, value 3
> * 1 with a delete of k with timestamp 1
> * 1 with k with timestamp 2, value 2
> The column of k has a summing combiner set on it. The issue here is that
> depending on how the major compactions play out, differing values with
> result. If all 3 files compact, the correct value of 2 will result. However,
> if 1 & 3 compact first, they will aggregate to 5. And then the delete will
> fall after the combined value, resulting in the result 5 to persist.
> First and foremost, this should be documented. I think to remedy this,
> combiners should only be used on full MajC, not not full ones. This may
> necessitate a special flag or a new combiner that implemented the proper
> semantics.
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