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