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From "Max Lapan (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HBASE-5416) Improve performance of scans with some kind of filters.
Date Mon, 02 Jul 2012 08:53:47 GMT

     [ https://issues.apache.org/jira/browse/HBASE-5416?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel

Max Lapan updated HBASE-5416:

    Attachment: Filtered_scans_v7.patch

Implemented benchmark of joined scanners.
You can run it with {{mvn test -P localTests --Dtest=TestJoinedScanners}}. It lasts for about
an hour, so, don't foreget to increase {{forkedProcessTimeoutInSeconds}} it pom.xml file.

On my notebook I got the following output:

2012-06-29 22:12:00,182 INFO  [main] regionserver.TestJoinedScanners(102): Make 100000 rows,
total size = 9765.0 MB
2012-06-29 22:56:51,231 INFO  [main] regionserver.TestJoinedScanners(128): Data generated
in 2691.048310914 seconds
2012-06-29 23:03:03,865 INFO  [main] regionserver.TestJoinedScanners(152): Slow scanner finished
in 372.634075184 seconds, got 1000 rows
2012-06-29 23:04:02,443 INFO  [main] regionserver.TestJoinedScanners(172): Joined scanner
finished in 58.577552657 seconds, got 1000 rows
2012-06-29 23:09:41,837 INFO  [main] regionserver.TestJoinedScanners(195): Slow scanner finished
in 339.394307354 seconds, got 1000 rows

I run slow scanners test twice to be sure that it's not a cache effect. So, it's about 5.7
times speedup on this toy data.

> Improve performance of scans with some kind of filters.
> -------------------------------------------------------
>                 Key: HBASE-5416
>                 URL: https://issues.apache.org/jira/browse/HBASE-5416
>             Project: HBase
>          Issue Type: Improvement
>          Components: filters, performance, regionserver
>    Affects Versions: 0.90.4
>            Reporter: Max Lapan
>            Assignee: Max Lapan
>         Attachments: 5416-Filtered_scans_v6.patch, 5416-v5.txt, 5416-v6.txt, Filtered_scans.patch,
Filtered_scans_v2.patch, Filtered_scans_v3.patch, Filtered_scans_v4.patch, Filtered_scans_v5.1.patch,
Filtered_scans_v5.patch, Filtered_scans_v7.patch
> When the scan is performed, whole row is loaded into result list, after that filter (if
exists) is applied to detect that row is needed.
> But when scan is performed on several CFs and filter checks only data from the subset
of these CFs, data from CFs, not checked by a filter is not needed on a filter stage. Only
when we decided to include current row. And in such case we can significantly reduce amount
of IO performed by a scan, by loading only values, actually checked by a filter.
> For example, we have two CFs: flags and snap. Flags is quite small (bunch of megabytes)
and is used to filter large entries from snap. Snap is very large (10s of GB) and it is quite
costly to scan it. If we needed only rows with some flag specified, we use SingleColumnValueFilter
to limit result to only small subset of region. But current implementation is loading both
CFs to perform scan, when only small subset is needed.
> Attached patch adds one routine to Filter interface to allow filter to specify which
CF is needed to it's operation. In HRegion, we separate all scanners into two groups: needed
for filter and the rest (joined). When new row is considered, only needed data is loaded,
filter applied, and only if filter accepts the row, rest of data is loaded. At our data, this
speeds up such kind of scans 30-50 times. Also, this gives us the way to better normalize
the data into separate columns by optimizing the scans performed.

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