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From "Ted Yu (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-6427) Pluggable compaction and scan policies via coprocessors
Date Tue, 11 Sep 2012 02:48:07 GMT

    [ https://issues.apache.org/jira/browse/HBASE-6427?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13452669#comment-13452669

Ted Yu commented on HBASE-6427:

In the new APIs, some return null as InternalScanner:
+  public InternalScanner preFlushScannerOpen(final ObserverContext<RegionCoprocessorEnvironment>
+      final Store store, final KeyValueScanner memstoreScanner, final InternalScanner s)
+      throws IOException {
+    return null;
some return the passed in scanner:
+  public InternalScanner preFlush(ObserverContext<RegionCoprocessorEnvironment> e,
Store store,
+      InternalScanner scanner) throws IOException {
+    return scanner;
I wonder why the difference.

This feature isn't marked as incompatible feature.
If 0.94.1 user has some jar with custom BaseRegionObserver implementation, I wonder if he/she
needs to recompile his/her code to generate new jar.
> Pluggable compaction and scan 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
>             Fix For: 0.96.0, 0.94.2
>         Attachments: 6427-0.94-addendum.txt, 6427-0.94.txt, 6427-notReady.txt, 6427-v10.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
> 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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