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https://issues.apache.org/jira/browse/HBASE-6427?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13424671#comment-13424671
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Zhihong Ted Yu commented on HBASE-6427:
---------------------------------------
There is no intersection between memstore scanners and store scanners.
The arbitrary number of scanners is due to the following construct:
{code}
+ for (RegionEnvironment env: coprocessors) {
+ if (env.getInstance() instanceof RegionObserver) {
+ ctx = ObserverContext.createAndPrepare(env, ctx);
+ try {
+ s = ((RegionObserver) env.getInstance()).preCompactScannerOpen(ctx,
store, scanners,
+ scanType, earliestPutTs, s);
{code}
I think we should reduce the complexity (due to scanner chaining) for
preCompactScannerOpen().
If we don't provide a working model for scanner chaining, there is no need to
introduce construct for chaining scanners.
> Pluggable compaction policies via coprocessors
> ----------------------------------------------
>
> Key: HBASE-6427
> URL: https://issues.apache.org/jira/browse/HBASE-6427
> Project: HBase
> Issue Type: New Feature
> Reporter: Lars Hofhansl
> Assignee: Lars Hofhansl
> Priority: Minor
> Attachments: 6427-notReady.txt, 6427-v1.txt, 6427-v2.txt,
> 6427-v3.txt, 6427-v4.txt, 6427-v5.txt, 6427-v7.txt
>
>
> When implementing higher level stores on top of HBase it is necessary to
> allow dynamic control over how long KVs must be kept around.
> Semi-static config options for ColumnFamilies (# of version or TTL) is not
> sufficient.
> This can be done with a few additional coprocessor hooks, or by makeing
> Store.ScanInfo pluggable.
> Was:
> The simplest way to achieve this is to have a pluggable class to determine
> the smallestReadpoint for Region. That way outside code can control what KVs
> to retain.
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