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https://issues.apache.org/jira/browse/HBASE-9778?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Lars Hofhansl updated HBASE-9778:
---------------------------------
Description:
The issue of slow seeking in ExplicitColumnTracker was brought up by
[~vrodionov] on the dev list.
My idea here is to avoid the seeking if we know that there aren't many versions
to skip.
How do we know? We'll use the column family's VERSIONS setting as a hint. If
VERSIONS is set to 1 (or maybe some value < 10) we'll avoid the seek and call
SKIP repeatedly.
HBASE-9769 has some initial number for this approach:
Interestingly it depends on which column(s) is (are) selected.
Some numbers: 4m rows, 5 cols each, 1 cf, 10 bytes values, VERSIONS=1,
everything filtered at the server with a ValueFilter. Everything measured in
seconds.
Without patch:
||Wildcard||Col 1||Col 2||Col 4||Col 5||Col 2+4||
|6.4|8.5|14.3|14.6|11.1|20.3|
With patch:
||Wildcard||Col 1||Col 2||Col 4||Col 5||Col 2+4||
|6.4|8.4|8.9|9.9|6.4|10.0|
Variation here was +- 0.2s.
So with this patch scanning is 2x faster than without in some cases, and never
slower. No special hint needed, beyond declaring VERSIONS correctly.
was:
The issue of slow seeking in ExplicitColumnTracker was brought up by
[~vrodionov] on the dev list.
My idea here is to avoid the seeking if we know that there aren't many rows to
skip.
How do we know? We'll use the column family's VERSIONS setting as a hint. If
VERSIONS is set to 1 (or maybe some value < 10) we'll avoid the seek and call
SKIP repeatedly.
HBASE-9769 has some initial number for this approach:
Interestingly it depends on which column(s) is (are) selected.
Some numbers: 4m rows, 5 cols each, 1 cf, 10 bytes values, VERSIONS=1,
everything filtered at the server with a ValueFilter. Everything measured in
seconds.
Without patch:
||Wildcard||Col 1||Col 2||Col 4||Col 5||Col 2+4||
|6.4|8.5|14.3|14.6|11.1|20.3|
With patch:
||Wildcard||Col 1||Col 2||Col 4||Col 5||Col 2+4||
|6.4|8.4|8.9|9.9|6.4|10.0|
Variation here was +- 0.2s.
So with this patch scanning is 2x faster than without in some cases, and never
slower. No special hint needed, beyond declaring VERSIONS correctly.
> Avoid seeking to next column in ExplicitColumnTracker when possible
> -------------------------------------------------------------------
>
> Key: HBASE-9778
> URL: https://issues.apache.org/jira/browse/HBASE-9778
> Project: HBase
> Issue Type: Bug
> Reporter: Lars Hofhansl
> Assignee: Lars Hofhansl
> Fix For: 0.98.0, 0.94.13, 0.96.1
>
> Attachments: 9778-0.94.txt, 9778-trunk.txt
>
>
> The issue of slow seeking in ExplicitColumnTracker was brought up by
> [~vrodionov] on the dev list.
> My idea here is to avoid the seeking if we know that there aren't many
> versions to skip.
> How do we know? We'll use the column family's VERSIONS setting as a hint. If
> VERSIONS is set to 1 (or maybe some value < 10) we'll avoid the seek and call
> SKIP repeatedly.
> HBASE-9769 has some initial number for this approach:
> Interestingly it depends on which column(s) is (are) selected.
> Some numbers: 4m rows, 5 cols each, 1 cf, 10 bytes values, VERSIONS=1,
> everything filtered at the server with a ValueFilter. Everything measured in
> seconds.
> Without patch:
> ||Wildcard||Col 1||Col 2||Col 4||Col 5||Col 2+4||
> |6.4|8.5|14.3|14.6|11.1|20.3|
> With patch:
> ||Wildcard||Col 1||Col 2||Col 4||Col 5||Col 2+4||
> |6.4|8.4|8.9|9.9|6.4|10.0|
> Variation here was +- 0.2s.
> So with this patch scanning is 2x faster than without in some cases, and
> never slower. No special hint needed, beyond declaring VERSIONS correctly.
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