[
https://issues.apache.org/jira/browse/HBASE-17125?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16057017#comment-16057017
]
ramkrishna.s.vasudevan commented on HBASE-17125:
------------------------------------------------
I was following this discussion previously and lost track. I have seen this
problem consistently arising. In all the different JIRAs related to this the
fix inside the core was always having some side effects one way or the other.
For the Visibility labels and ACL comment from Anoop, I think if we remove the
Logic in VisiblityLabelFilter's filterKV to get the max number of versions and
just add the new filter at the end in VisibiityController and set
scan.setMaxVersion() all the visibilty tests should still pass. Can you try it
out once [~zghaobac]?
I think having a javadoc and a new filter for the user in case where he really
wants multiple versions to be returned back even while filtering means he can
try using the new filter provided (if it is covering all the cases) as the core
side changes are minimal and most importantly bug free.
IMHO - it is fine with me to add a new filter and expose it to user for those
who need this filter + version specific usage.
> 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.
--
This message was sent by Atlassian JIRA
(v6.4.14#64029)
