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https://issues.apache.org/jira/browse/HBASE-17125?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16056973#comment-16056973
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Anoop Sam John commented on HBASE-17125:
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What Ted 2 reasons why I fear abt the way of asking new Filter usage.. I did
not check his suggestion fully wrt code and side effects if any.. But IMHO we
should try it out.. With out much perf penalty if we can do, why not! If the
code itself can handle this that is always better and users will be much more
happy(Than they have to remember and use another filter).. Lets be open for
all possible ways. My request he would be pls see possible ways with which we
can solve it on our own.. All agree here that the present situation is a bug
and really bad behave from system. We never give back deterministic results.
(All depends on other factors like compaction done or not etc)
> Inconsistent result when use filter to read data
> ------------------------------------------------
>
> Key: HBASE-17125
> URL: https://issues.apache.org/jira/browse/HBASE-17125
> Project: HBase
> Issue Type: Bug
> Reporter: Guanghao Zhang
> Assignee: Guanghao Zhang
> Priority: Critical
> Fix For: 2.0.0
>
> Attachments: example.diff, HBASE-17125.master.001.patch,
> HBASE-17125.master.002.patch, HBASE-17125.master.002.patch,
> HBASE-17125.master.003.patch, HBASE-17125.master.004.patch,
> HBASE-17125.master.005.patch, HBASE-17125.master.006.patch,
> HBASE-17125.master.007.patch, HBASE-17125.master.008.patch,
> HBASE-17125.master.009.patch, HBASE-17125.master.009.patch,
> HBASE-17125.master.010.patch, HBASE-17125.master.011.patch
>
>
> Assume a cloumn's max versions is 3, then we write 4 versions of this column.
> The oldest version doesn't remove immediately. But from the user view, the
> oldest version has gone. When user use a filter to query, if the filter skip
> a new version, then the oldest version will be seen again. But after compact
> the region, then the oldest version will never been seen. So it is weird for
> user. The query will get inconsistent result before and after region
> compaction.
> The reason is matchColumn method of UserScanQueryMatcher. It first check the
> cell by filter, then check the number of versions needed. So if the filter
> skip the new version, then the oldest version will be seen again when it is
> not removed.
> Have a discussion offline with [~Apache9] and [~fenghh], now we have two
> solution for this problem. The first idea is check the number of versions
> first, then check the cell by filter. As the comment of setFilter, the filter
> is called after all tests for ttl, column match, deletes and max versions
> have been run.
> {code}
> /**
> * Apply the specified server-side filter when performing the Query.
> * Only {@link Filter#filterKeyValue(Cell)} is called AFTER all tests
> * for ttl, column match, deletes and max versions have been run.
> * @param filter filter to run on the server
> * @return this for invocation chaining
> */
> public Query setFilter(Filter filter) {
> this.filter = filter;
> return this;
> }
> {code}
> But this idea has another problem, if a column's max version is 5 and the
> user query only need 3 versions. It first check the version's number, then
> check the cell by filter. So the cells number of the result may less than 3.
> But there are 2 versions which don't read anymore.
> So the second idea has three steps.
> 1. check by the max versions of this column
> 2. check the kv by filter
> 3. check the versions which user need.
> But this will lead the ScanQueryMatcher more complicated. And this will break
> the javadoc of Query.setFilter.
> Now we don't have a final solution for this problem. Suggestions are welcomed.
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