hbase-issues mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "hongbin ma (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-14269) FuzzyRowFilter omits certain rows when multiple fuzzy key exist
Date Wed, 26 Aug 2015 06:26:46 GMT

    [ https://issues.apache.org/jira/browse/HBASE-14269?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14712582#comment-14712582

hongbin ma commented on HBASE-14269:

As [~vrodionov] suggested I performed another test with TestFuzzyRowFilterEndToEnd:

50 fuzzykeys:

||  ||Pre HBASE-13761||HBASE-14269||
|runTest1's first run|180ms|204ms|
|runTest1's second run|82ms|62ms|
|runTest2's first run|209ms|230ms|
|runTest2's second run|92ms|109ms|

100 fuzzykeys: 
||  ||Pre HBASE-13761||HBASE-14269||
|runTest1's first run|183ms|177ms|
|runTest1's second run|82ms|56ms|
|runTest2's first run|218ms|214ms|
|runTest2's second run|98ms|107ms|

500 fuzykeys:
||  ||Pre HBASE-13761||HBASE-14269||
|runTest1's first run|184ms|192ms|
|runTest1's second run|72ms|61ms|
|runTest2's first run|260ms|226ms|
|runTest2's second run|127ms|101ms|

Unfortunately the I don't think post HBASE-13761 optimizations have boost the performance
very much.
I don't have the condition to profile very large dataset,  [~vrodionov] will you please share
your numbers?

Despite the bad news, the bug in HBASE-13761 still needs to be fixed.
It seems the new approach is not degrading when compared with  pre HBASE-13761. 
And as the number of fuzzykeys increases, HBASE-14269 tends to be faster than  pre HBASE-13761.
So I thinks it is okay to commit this patch.

Suggestions for FuzzyRowFilter users:
FuzzyRowFilter is good when you have handful of fuzzy filters, when the number of fuzzy filters
grow out of control (In apache Kylin we witnessed user queries caused using more than 100000
fuzzy filters) Normal it will bring more performance issues than benefit.

> FuzzyRowFilter omits certain rows when multiple fuzzy key exist
> ---------------------------------------------------------------
>                 Key: HBASE-14269
>                 URL: https://issues.apache.org/jira/browse/HBASE-14269
>             Project: HBase
>          Issue Type: Bug
>          Components: Filters
>            Reporter: hongbin ma
>            Assignee: hongbin ma
>             Fix For: 2.0.0, 1.2.0, 1.3.0, 0.98.15, 1.0.3, 1.1.3
>         Attachments: HBASE-14269-v1.patch, HBASE-14269-v2.patch, HBASE-14269.patch
> https://issues.apache.org/jira/browse/HBASE-13761 introduced a RowTracker in FuzzyRowFilter
to avoid performing getNextForFuzzyRule() for each fuzzy key on each getNextCellHint() by
maintaining a list of possible row matches for each fuzzy key. The implementation assumes
that the prepared rows will be matched one by one, so it removes the first row in the list
as soon as it is used. However, this approach may lead to omitting rows in some cases:
> Consider a case where we have two fuzzy keys:
> 1?1
> 2?2
> and the data is like:
> 000
> 111
> 112
> 121
> 122
> 211
> 212
> when the first row 000 fails to match, RowTracker will update possible row matches with
cell 000 and fuzzy keys 1?1,2?2. This will populate RowTracker with 101 and 202. Then 101
is popped out of RowTracker, hint the scanner to go to row 101. The scanner will get 111 and
find it is a match, and continued to find that 112 is not a match, getNextCellHint will be
called again. Then comes the bug: Row 101 has been removed out of RowTracker, so RowTracker
will jump to 202. As you see row 121 will be omitted, but it is actually a match for fuzzy
key 1?1.
> I will illustrate the bug by adding a new test case in TestFuzzyRowFilterEndToEnd. Also
I will provide the bug fix in my patch. The idea of the new solution is to maintain a priority
queue for all the possible match rows for each fuzzy key, and whenever getNextCellHint is
called, the elements in the queue that are smaller than the parameter currentCell will be
updated(and re-insert into the queue). The head of queue will always be the "Next cell hint".

This message was sent by Atlassian JIRA

View raw message