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From "Kannan Muthukkaruppan (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HBASE-3211) Key (Index) Only Fetches
Date Thu, 11 Nov 2010 15:55:16 GMT

    [ https://issues.apache.org/jira/browse/HBASE-3211?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12931050#action_12931050

Kannan Muthukkaruppan commented on HBASE-3211:

Nicolas: Hear your concern about filter vs. map approach. And if a user mixes this with other
filters using a compound filter (such as "or" and "and" filter) and if some of the filters
involved are "value" filters, then the fact the filter implementation has side-effects makes
the behavior dependent on the order in which the filters are processed.

Perhaps a middle ground is to at least not expose this feature as a "filter" to the end user.
Instead, we could add a explicit method (on Get & Scan), say "keysOnly". But its implementation
could maybe still use the filter approach--- i.e. just before we serialize the Get/Scan request,
if keysOnly() is requested, we could tack on this special (internal-only) filter to the very
top of any user provided filters. This will prevent the ambiguous cases we are worried about
from arising, and will still interop nicely with other filters.

> Key (Index) Only Fetches
> ------------------------
>                 Key: HBASE-3211
>                 URL: https://issues.apache.org/jira/browse/HBASE-3211
>             Project: HBase
>          Issue Type: Improvement
>            Reporter: Kannan Muthukkaruppan
>            Assignee: Jonathan Gray
>             Fix For: 0.90.0
>         Attachments: HBASE-3211-v2.patch, HBASE-3211-v3.patch
> When you retrieve data from HBase you get Key (Row+Column+Timestamp) + Values. 
> It would be nice to have a mode where we only fetch the keys (i.e. the index) but not
the values.

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