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https://issues.apache.org/jira/browse/HBASE-5416?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13532937#comment-13532937
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Ted Yu commented on HBASE-5416:
-------------------------------
I ran test suite with the following change based on patch v8:
{code}
+ public static KeyValue createFirstOnRow(final byte [] row, int roffset,
short rlength) {
+ return new KeyValue(row, roffset, rlength,
+ null, 0, 0, null, 0, 0, HConstants.LATEST_TIMESTAMP, Type.Maximum,
null, 0, 0);
+ }
{code}
I got:
{code}
[INFO] HBase ............................................. SUCCESS [3.012s]
[INFO] HBase - Common .................................... SUCCESS [14.056s]
[INFO] HBase - Protocol .................................. SUCCESS [13.557s]
[INFO] HBase - Client .................................... SUCCESS [0.654s]
[INFO] HBase - Hadoop Compatibility ...................... SUCCESS [0.733s]
[INFO] HBase - Hadoop One Compatibility .................. SUCCESS [1.753s]
[INFO] HBase - Server .................................... SUCCESS [44:06.793s]
[INFO] HBase - Hadoop Two Compatibility .................. SUCCESS [9.770s]
[INFO] HBase - Integration Tests ......................... SUCCESS [3.340s]
[INFO] HBase - Examples .................................. SUCCESS [30.981s]
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
{code}
For TestJoinedScanners:
{code}
2012-12-14 19:40:01,764 INFO [pool-1-thread-1]
regionserver.TestJoinedScanners(168): Slow scanner finished in 31.798885086
seconds, got 100 rows
2012-12-14 19:40:03,710 INFO [pool-1-thread-1]
regionserver.TestJoinedScanners(168): Joined scanner finished in 1.946100741
seconds, got 100 rows
...
2012-12-14 19:43:29,757 INFO [pool-1-thread-1]
regionserver.TestJoinedScanners(168): Slow scanner finished in 44.846782189
seconds, got 100 rows
2012-12-14 19:43:31,871 INFO [pool-1-thread-1]
regionserver.TestJoinedScanners(168): Joined scanner finished in 2.11452886
seconds, got 100 rows
{code}
> 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
> Fix For: 0.96.0
>
> 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, HBASE-5416-v7-rebased.patch, HBASE-5416-v8.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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