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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (PHOENIX-2417) Compress memory used by row key byte[] of guideposts
Date Sat, 16 Jan 2016 02:32:39 GMT

    [ https://issues.apache.org/jira/browse/PHOENIX-2417?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15102935#comment-15102935
] 

ASF GitHub Bot commented on PHOENIX-2417:
-----------------------------------------

Github user JamesRTaylor commented on a diff in the pull request:

    https://github.com/apache/phoenix/pull/147#discussion_r49925693
  
    --- Diff: phoenix-core/src/main/java/org/apache/phoenix/iterate/BaseResultIterators.java
---
    @@ -510,14 +532,18 @@ private static String toString(List<byte[]> gps) {
                     endRegionKey = regionInfo.getEndKey();
                     keyOffset = ScanUtil.getRowKeyOffset(regionInfo.getStartKey(), endRegionKey);
                 }
    -            while (guideIndex < gpsSize
    -                    && (Bytes.compareTo(currentGuidePost = gps.get(guideIndex),
endKey) <= 0 || endKey.length == 0)) {
    -                Scan newScan = scanRanges.intersectScan(scan, currentKey, currentGuidePost,
keyOffset, false);
    -                scans = addNewScan(parallelScans, scans, newScan, currentGuidePost, false,
regionLocation);
    -                currentKey = currentGuidePost;
    -                guideIndex++;
    -            }
    -            Scan newScan = scanRanges.intersectScan(scan, currentKey, endKey, keyOffset,
true);
    +            try {
    +                while (guideIndex < gpsSize && (currentGuidePost.compareTo(endKey)
<= 0 || endKey.length == 0)) {
    +                    Scan newScan = scanRanges.intersectScan(scan, currentKeyBytes, currentGuidePostBytes,
keyOffset,
    +                            false);
    +                    scans = addNewScan(parallelScans, scans, newScan, currentGuidePostBytes,
false, regionLocation);
    +                    currentKeyBytes = currentGuidePost.copyBytes();
    +                    currentGuidePost = CodecUtils.decode(decoder, input);
    +                    currentGuidePostBytes = currentGuidePost.copyBytes();
    --- End diff --
    
    And here


> Compress memory used by row key byte[] of guideposts
> ----------------------------------------------------
>
>                 Key: PHOENIX-2417
>                 URL: https://issues.apache.org/jira/browse/PHOENIX-2417
>             Project: Phoenix
>          Issue Type: Sub-task
>            Reporter: James Taylor
>            Assignee: Ankit Singhal
>             Fix For: 4.7.0
>
>         Attachments: PHOENIX-2417.patch, PHOENIX-2417_encoder.diff, PHOENIX-2417_v2_wip.patch
>
>
> We've found that smaller guideposts are better in terms of minimizing any increase in
latency for point scans. However, this increases the amount of memory significantly when caching
the guideposts on the client. Guidepost are equidistant row keys in the form of raw byte[]
which are likely to have a large percentage of their leading bytes in common (as they're stored
in sorted order. We should use a simple compression technique to mitigate this. I noticed
that Apache Parquet has a run length encoding - perhaps we can use that.



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