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From "Ted Yu (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-16296) Reverse scan performance degrades when scanner cache size matches page filter size
Date Fri, 29 Jul 2016 22:48:20 GMT

    [ https://issues.apache.org/jira/browse/HBASE-16296?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15400164#comment-15400164
] 

Ted Yu commented on HBASE-16296:
--------------------------------

I wonder if the following change would help :
{code}
diff --git a/hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/HRegion.java
b/hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/HRegion.java
index 89e723e..fa3836f 100644
--- a/hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/HRegion.java
+++ b/hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/HRegion.java
@@ -5951,6 +5951,10 @@ public class HRegion implements HeapSize, PropagatingConfigurationObserver,
Regi
           // Technically, if we hit limits before on this row, we don't need this call.
           if (filterRowKey(current)) {
             incrementCountOfRowsFilteredMetric(scannerContext);
+            if (isFilterDoneInternal()) {
+                return scannerContext.setScannerState(NextState.NO_MORE_VALUES).hasMoreValues();
+            }
+
             // Typically the count of rows scanned is incremented inside #populateResult.
However,
             // here we are filtering a row based purely on its row key, preventing us from
calling
             // #populateResult. Thus, perform the necessary increment here to rows scanned
metric
{code}

> Reverse scan performance degrades when scanner cache size matches page filter size
> ----------------------------------------------------------------------------------
>
>                 Key: HBASE-16296
>                 URL: https://issues.apache.org/jira/browse/HBASE-16296
>             Project: HBase
>          Issue Type: Bug
>            Reporter: James Taylor
>         Attachments: 16296-MAYBE.txt, generatedata-snippet.java, repro-snippet.java
>
>
> When a reverse scan is done, the server seems to not know it's done when the scanner
cache size matches the number of rows in a PageFilter. See PHOENIX-3121 for how this manifests
itself. We have a standalone, pure HBase API reproducer too that I'll attach (courtesy of
[~churromorales] and [~mujtabachohan]).



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